ARTICLE OPEN ACCESS

Heterozygous STUB1 missense variants causeataxia cognitive decline and STUB1mislocalizationDong-Hui Chen MD PhD Caitlin Latimer MD PhD Mayumi Yagi PhD Mesaki Kenneth Ndugga-Kabuye MD

Elyana Heigham BS Suman Jayadev MD James S Meabon PhD Christopher M Gomez MD PhD

C Dirk Keene MD PhD David G Cook PhD Wendy H Raskind MD PhD and Thomas D Bird MD

Neurol Genet 20206e397 doi101212NXG0000000000000397

Correspondence

Dr Bird

tomnrozuwedu

AbstractObjectiveTo identify the genetic cause of autosomal dominant ataxia complicated by behavioral ab-normalities cognitive decline and autism in 2 families and to characterize brain neuropatho-logic signatures of dominant STUB1-related ataxia and investigate the effects of pathogenicvariants on STUB1 localization

MethodsClinical and research-based exome sequencing was used to identify the causative variants forautosomal dominant ataxia in 2 families Gross and microscopic neuropathologic evaluationswere performed on the brains of 4 affected individuals in these families

ResultsMutations in STUB1 have been primarily associated with childhood-onset autosomal recessiveataxia but here we report heterozygous missense variants in STUB1 (pIle53Thr and pThe37-Leu) confirming the recent reports of autosomal dominant inheritance Cerebellar atrophy onimaging and cognitive deficits often preceded ataxia Unique neuropathologic examination of the4 brains showed the marked loss of Purkinje cells (PCs) without microscopic evidence ofsignificant pathology outside the cerebellum The normal pattern of polarized somatodendriticSTUB1 protein expression in PCs was lost resulting in aberrant STUB1 localization in the distalPC dendritic arbors

ConclusionsThis study confirms a dominant inheritance pattern in STUB1-ataxia in addition to a recessiveone and documents its association with cognitive and behavioral disability including autism Inthe most extensive analysis of cerebellar pathology in this disease we demonstrate disruption ofSTUB1 protein in PCs as part of the underlying pathogenesis

From the Department of Neurology (D-HC EH SJ TDB) University of Washington Seattle Department of Pathology (CL CDK) Neuropathology Division University ofWashington Seattle Geriatric Research Education and Clinical Center (GRECC) (MY DGC WHR TDB) VA Puget Sound Health Care System Seattle WA Department ofMedicine (MKN-K WHR TDB) Division of Medical Genetics University of Washington Seattle Mental Illness Research Education and Clinical Center (MIRECC) (JSM WHR)VA Puget Sound Health Care System Seattle WA Department of Psychiatry and Behavioral Sciences (JSM WHR) University of Washington Seattle Department of Neurology(CMG) University of Chicago IL Department of Medicine (DGC) Division of Gerontology and Geriatric Medicine University of Washington Seattle and Department ofPharmacology (DGC) University of Washington Seattle

Go to NeurologyorgNG for full disclosures Funding information is provided at the end of the article

The Article Processing Charge was funded by the authors

This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License 40 (CC BY-NC-ND) which permits downloadingand sharing the work provided it is properly cited The work cannot be changed in any way or used commercially without permission from the journal

Copyright copy 2020 The Author(s) Published by Wolters Kluwer Health Inc on behalf of the American Academy of Neurology 1

There are more than 40 genetic types of autosomal dominantcerebellar ataxia referred to as the spinocerebellar ataxias(SCAs)1 In addition there are more than 100 autosomal re-cessive disorders in which cerebellar ataxia is a prominentfeature variably denoted as spinocerebellar ataxia recessive(SCAR) or ARCA (autosomal recessive cerebellar ataxia)1

One recessive variety SCAR-16 is caused by homozygous orcompound heterozygous mutations in the STUB1 (Stip1 ho-mologous and Ubox-containing protein 1) gene23 Mostindividuals with SCAR-16 have an onset of a cerebellar syn-drome in childhood or adolescence sometimes associated withcognitive disability The single brain autopsy reported showedsevere loss of Purkinje cells (PCs) and neurons of the granularlayer accompanied by reactive Bergmann gliosis but it lackedinformation about STUB1 staining in the cerebellum4 Auto-somal dominant inheritance of heterozygous STUB1 variantshave been recently been reported but without neuropathologicevaluations56

STUB1 protein also called C terminus of HSP 70 interactingprotein (CHIP) contains a tetratricopeptide repeat anda U-box Among other functions it is an E3 ubiquitin ligasecochaperone that targets a broad range of chaperone proteinsubstrates including Hsp70 Hsc70 Hsp90 and DNA poly-merase beta for ubiquitin proteasome degradation7

We report 2 families with autosomal dominant cerebellar ataxiaprogressive cognitive decline and in one individual childhoodautism spectrum disorder associated with missense variants inSTUB1 The availability of 4 brain autopsies from these familiesallowed a detailed evaluation of the cerebellar pathology andrevealed aberrant intracellular location of STUB1

MethodsStandard protocol approvals registrationsand patient consentsRecruitment and sampling of the families was approved by theInstitutional Review Board of the University of Washington(UW) and informed consent was provided by all patients

Genetics studiesThe pedigrees of the 2 families with familial cerebellar ataxia areshown in figure 1 A and B Clinical testing for the commonhereditary ataxias was performed for the probands III-1 infamily A and III-2 in family B as described below in the clinicaldescriptions Blood samples from the affected and unaffectedpatients (indicated in the pedigree) were collected and geno-mic DNA was extracted by standard methods

Exome sequencing was performed at the UW Center for Pre-cision Diagnostics on affected patients A III-1 and A IV-1Target enrichment by NimbleGen solution capture array andexome sequencing were performed and processed using Illu-mina HiSeq Analysis Software as previously described8 Thereads were aligned and compared with the Homo SapiensGRCh37 reference genome Sequences that failed GenomeAnalysis Toolkit quality filters were not further consideredFiltering of the variants was based on (1) coding region se-quence effectmdashmissense nonsense coding indels and splicesites (2) heterozygosity given the autosomal dominant in-heritance pattern of the disease in the family (3) shared byboth exomes or not read in one of the exomes (specified as ldquoNrdquoin the exome sequence data) (4) variant frequencymdashabsencefrom the 1000 Genomes Project database and frequencythreshold less than 00001 in gnomAD (5) high evolutionaryconservation gt3 by Genomic Evolutionary Rate Profiling(GERP)9 (6) a predicted damaging or probably damagingeffect on protein structure and function by Sorting IntolerantFrom Tolerant10 and PolyPhen1112 and (7) Combined An-notation Dependent Depletion (CADD) score13 gt15 Variantsthat met these criteria were prioritized by gene expressionfunction in cerebellum information from animal models andrelevance to neurologic diseases

To confirm the exome variants and to investigate its cose-gregation with the disease in family A we performed PCRcapillary sequencing using customized primers to amplify thefragment encompassing the candidate variants from genomicDNA using Hot Start Taq Polymerase (Qiagen Hilden Ger-many) as previously described14

Neuropathologic studiesIn both families consent for autopsy was obtained from thelegal next of kin according to the protocols approved bythe UW Institutional Review Board At the time of autopsy thebrain was removed in the usual fashion In family A for patientsII-2 and III-1 the left halves were coronally sectioned andfrozen for possible biochemical studies and the right halveswere fixed in formalin For patient A IV-1 the entire brain wasfixed in formalin After fixation the cerebrum was sectionedcoronally the brainstem was sectioned axially and the cere-bellum sectioned sagittally In family B the brain was fixed in10 neutral buffered formalin After fixation the cerebrum wassectioned coronally and the cerebellum and brainstem weresectioned axially

A microtome was used to cut 4 μm-thick tissue sections fromformalin-fixed paraffin-embedded tissue blocks Hematoxylinand eosin (HampE) Luxol fast blue (LFB) and Bielschowsky

GlossaryCADD = Combined Annotation Dependent Depletion CHIP = C terminus of HSP 70 interacting proteinGERP = GenomicEvolutionary Rate Profiling HampE = hematoxylin and eosin PC = Purkinje cell SCA = Spinocerebellar Ataxia SCAR =Spinocerebellar Ataxia Recessive UW = University of Washington WAIS-R = Wechsler Adult Intelligence ScalemdashRevised

2 Neurology Genetics | Volume 6 Number 2 | April 2020 NeurologyorgNG

silver stained slides were prepared Using previously optimizedconditions immunohistochemistry was performed usinga Leica Bond III Fully Automated IHC and ISH StainingSystem (Leica Biosystems Wetzlar Germany) The sectionswere immunostained with mouse monoclonal antibody againstpaired helical filament tau (AT8 11000 dilution) (PierceTechnology Waltham MA) mouse monoclonal againstβ-amyloid (6E10 15000) (Covance Princeton NJ) ratmonoclonal against phosphorylated TDP-43 (ser409ser41011000) (Millipore Burlington MA) mouse monoclonalagainst α-synuclein (LB509 1500) (Invitrogen CarlsbadCA) rabbit polyclonal against glial fibrillar acidic protein(Z033401-2 12000) (DAKO-Agilent Santa Clara CA)mouse monoclonal against calbindin protein (CB-955 11000) (Sigma-Aldrich St Louis MO) mouse monoclonalagainst ubiquitin (ubi-1 150000) (Millipore) and mousemonoclonal against p62 (2C11 14000) Appropriate positiveand negative controls were included with each antibody andeach run

STUB1 immunofluorescence microscopyParaffin-embedded brain sections were stained using reagentsand protocols from a commercially available kit (Opal ManualIHC Kit Akoya Bioscience Menlo Park CA) The primaryantibodies used were anti-calbindin D28k (11000 dilutionEMD Millipore) anti-EAAT4 (1200 dilution Abcam Cam-bridge United Kingdom) and anti-STUB1 (11000 dilutionAbcam) Briefly the sections were deparaffinized in xyleneand rehydrated through graded alcohol and fixed in neutral-buffered formalin Heat-mediated antigen retrieval was

performed in AR6 buffer for 15 minutes at 98degC The sectionswere treated for 10 minutes in antibody diluentblock andincubated with primary antibody diluted in the same bufferThe slides were washed in tris-buffered saline and polysorbate20 incubated with the peroxidase-conjugated antimouserabbitsecondary antibody and then washed and incubated with Opalfluorescent substrate diluted in amplification buffer (Opal-650Opal-520 and Opal-570 presented as pseudocolored immu-nostaining in purple green and red respectively) The sectionswere washed and heat-treated to remove the antibody and thenblocked and incubated with the second primary antibody asfollowed by secondary and Opal substrate as before The cyclewas repeated once more with the third primary antibody Afterthe third cycle the sections were incubated briefly with Hoechst33256 rinsed with distilled H2O and mounted with ProLongDiamond Antifade Mountant (ThermoFisher Waltham MA)Confocal microscopy was performed using a Leica TCS SP5II microscope Confocal images were acquired with the LeicaApplication Suite and processed using identical data acqui-sition settings for the images in each specific figure Allconfocal images are single z-plane scans Postacquisitionimage processing and figure preparation were accomplishedusing Leica Application Suite and Photoshop software thatwere limited to linear contrast and brightness adjustmentsonly and were applied identically to all images regarding eachspecific figure

Data availabilityDeidentified data included in this study are available from thecorresponding author on reasonable request

Figure 1 Four generation pedigrees of 2 families with hereditary cerebellar ataxia and cognitive disability

If alive current age in years is shown below the symbol = deceased A = brain autopsy ASD = autism spectrumdisorder black symbol = affected with ataxiad = age at death The variant or wild-type STUB1 allele is shown for individuals who were tested

NeurologyorgNG Neurology Genetics | Volume 6 Number 2 | April 2020 3

ResultsClinical descriptionsFamily A The index case (III-1 in figure 1A) is a 60-year-oldman who developed cognitive problems and clumsiness in hisearly 40s He had 2 years of college education and wasemployed as a mechanical engineer Examination at 44 years ofage showed delayed but accurate responses to cognitive ques-tions saccadic interruptions in smooth pursuit eye movementsand random brief jerking movements of his hands and legsRepeat examination at 48 years of age showed a Mini-MentalStatus Examination score of 26 of 30 mild gait ataxia moderatedysarthria irregular smooth pursuit and saccadic eye move-ments and hyperactive tendon reflexes at the knees A brainMRI revealed cerebellar atrophy that appeared out of pro-portion to the relatively mild physical findings Formal neu-ropsychometric testing at 49 years of age revealed generallynormal intelligence but abnormal scores for executive functionand verbal memory (table 1) Repeat examination over the next10 years showed slow and steady progression of his disease Hisspeech remained slurred and his gait became more unsteadyalthough he was still ambulatory with a walker He hada stooped posture and was bradykinetic but had no rigidity andno tremor Repeat MRIs showed increased cerebellar atrophy(figure 2A) He had cognitive decline became less verbal andsometimes demonstrated agitation and belligerence Psycho-metric testing documented deterioration with deficiencies inverbal and visual memory general language ability processingspeed executive functions and abstract reasoning with manysubtests in the 1st to 10th percentile Medical comorbiditiesincluded adult-onset diabetes mellitus and central sleep apneatreated with nocturnal continuous positive airway pressureMedications included olanzapine lorazepam Neurontin andbaclofen Molecular testing for SCAs 1 2 3 6 7 8 14 and 12and DRPLA were negative He died at the age of 60 years in anassisted living facility and his brain autopsy was obtained

The father (II-2 in figure 1A) of the index patient had an onsetof cognitive problems and poor coordination in his early 60sHe had been a pilot mechanic and homebuilder A singleneurologic examination at 68 years of age revealed mild gaitataxia dysarthria poor hand coordination abnormal saccadiceye movements hyperactive knee reflexes and extensor plantarreflexes He had intact short-termmemory and could do simplearithmetic but exhibited paraphasias inability to performa three-step command or do a word problem in his head andhad concrete thinking and poor performance of the Luria handsequence His ataxia and cognitive problems progressed and hestarted using a wheelchair He died at the age of 79 years anda brain autopsy was obtained

The brother (III-3 in figure 1A) of the index patient had a ju-nior college education He had an onset of poor coordination inhis late 20s Examination at 34 years of age revealedmarked gaitataxia saccadic smooth pursuit eye movements with hyper-metric saccades dysarthria dysmetria and hyperactive tendonreflexes Detailed mental status examination revealed moderate

difficulty with memory andmarked problems with visual spatialskills calculations insight and judgment Wechsler Adult In-telligence ScalemdashRevised (WAIS-R) testing15 revealed a verbalIQ of 74 performance IQ of 68 and full scale IQ of 71 He waslabeled ldquodementedrdquo He had a childlike affect with in-appropriate and tangential responses MRI revealed markedcerebellar atrophyHe experienced both alcohol and drug abuseand died at the age of 45 years without autopsy

The daughter of the index patient (IV-1 in figure 1A) had anunremarkable labor and delivery and reached developmentalmotor milestones of childhood within the range of normal Shehad average to below-average grades in school and was able toattend community college but dropped out of several coursesAt 21 years of age formal psychological testing showed a verbalIQ score of 84 performance score of 83 and full scale score of83 (13th percentileWAIS-R) Her highest score was in readingrecognition (30th percentile) but other subscale scores werebelow the 20th percentile Special weaknesses were in digitspan object assembly arithmetic and visual spatial analysis Shehad great difficulty with social interactions and was labeled withldquoextreme shynessrdquo and avoidant personality disorder Sheseemed ldquodisconnected from realityrdquo was frequently teased andhad a ldquonervous breakdownrdquo at 13 years of age A detailedanalysis by a neuropsychologist at the age of 24 years demon-strated that she fell within the autism spectrum disorder WAIS-R IQ and memory testing was similar to the age of 21 yearswith mental arithmetic comprehension block design objectassembly and visual memory at or below the fifth percentile(table 1) Neurologic examination at the age of 24 years wasremarkable only for occasional saccadic interruptions in smoothpursuit and mild deep tendon hyper-reflexia She had no nys-tagmus no dysarthria no intention tremor and no gait ataxiaHowever because of her family history of hereditary ataxia shereceived a brain MRI that showed definite cerebellar atrophyOver the next 10 years there was no change in her neurologicexamination and she did not develop ataxia A repeat brainMRIat 32 years of age showed mild increase in the degree of cere-bellar atrophy and mild generalized cerebral volume loss thatwas greater than expected for her age (figure 2B) She movedout of state and began to deteriorate in her late 30s and early40s She developed gait ataxia and started using a wheelchairShe developed severe cognitive decline with confusion disori-entation poor judgment and deficient problem solving Shedeveloped bladder incontinence and became fully dependenton nursing care She died at the age of 43 years and her brainautopsy was obtained Her brother (IV-2) had a normal ex-amination and normal brain MRI at the age of 40 years

Family B The index patient (III-2 in figure 1B) was a womanwho developed difficulty with coordination mental confusionand a personality change at approximately 40 years of ageNeurologic examination at the age of 42 years revealed gaitataxia dysarthria gaze-evoked horizontal nystagmus and dys-metria Tendon reflexes and sensory examination were un-remarkable Brain MRI at the age of 48 years showed moderatecerebellar atrophy (figure 2 C andD) TheMini-Mental Status

4 Neurology Genetics | Volume 6 Number 2 | April 2020 NeurologyorgNG

Examination score was 28 of 30 Detailed formal neuro-psychological testing revealed intact verbal memory but withnumerous cognitive test scores at or below the fifth percentileand she was noted to have marked general difficulties in themanagement and production of cognitive processes (table 1)She was a college graduate and had been a schoolteacher butwas no longer able to perform her teaching duties Multiplegenetic tests for ataxia were all normal including SCAs 1 2 3 56 7 10 14 21 dentatorubral-pallidoluysian atrophy Frie-dreichrsquos ataxia and senataxin

Her family history was positive for additional affected peopleHer father had died at the age of 75 years with ataxia and herpaternal aunt died at the age of 73 years and had been usinga wheelchair for 10 years with ataxia Her paternal grandmotherdied at the age of 68 years after admission to a state mentalinstitution with ataxia cognitive decline and psychotic featuresThe patient had younger siblings who were not symptomaticone of whom (III-3) had a normal examination at the age of 56years and remains unaffected at the age of 67 years

The patient had a slowly progressive course eventually re-quiring a wheelchair Her personality change included episodesof agitation and belligerence treated with olanzapine Later inlife she developed a large excursion movement disorder of herupper and lower limbs that was described as an unusual wing-

Table 1 Neuropsychological testing

Family A IV-1 age 24

Wechsler AdultIntelligenceScalemdashRevised15

Wechsler MemoryScale Revised43

Verbal IQ 78 (7) Verbal memoryindex

27

Performance IQ 88(21)

Visual memoryindex

4

Full scale IQ 80 (9) General memoryindex

14

Mental arithmetic 5 Attentionconcentration index

2

Comprehension 5 Delayed memoryindex

30

Vocabulary 25 Immediate recall 29

Block design 5 Delayed recall 22

Object assembly 2 Digits forward 12

Digit symbols 50 Digits backward 26

Digit span 38 Visual memory spanforward

10

Similarities 9 Trail-making test A44 80

Information 50 Trail-making test B 10

Picture completion 84

Picture arrangement 75

Family A III-1 age 49

Woodcock Johnson testsof cognitive ability4546

Wide-rangeassessment ofmemory andlearning47

Board cognitive ability 12 Picture memory 63

Memory for name 43 Design memory 9

Memory for sentences 1 Verbal memory 9

Visual matching 2 Story memory 2

Incomplete words 20 Wisconsin cardsorting48

Visual closure 44 All subtests 2ndash

12

Picture vocabulary 72

Analysis synthesis 33

Family B III-1 age 42

Wechsler AdultIntelligence ScaleRevised15

Controlled oralword associationtest49

Digit span lt10 FAS lt1

Picture completion 37 Animals lt1

Picture arrangement 50

Block design 10

Table 1 Neuropsychological testing (continued)

Family B III-1 age 42

Wechsler AdultIntelligence ScaleRevised15

Controlled oralword associationtest49

Wechsler memoryscale

Wisconsin cardsorting test48

Verbal immediate 95 Categories 16

Verbal delayed 75 No presev errors 30

Visual immediate 37 No error 34

Visual delayed 25

California verbal learningtest50

Hooper visualorganizationtest49

20

Trial 1 2

Trial 5 lt1

B List 2

Immediate recall 14

Cued 14

Delayed recall 2

Cued 14

Recognition 14

Intrusions 85

NeurologyorgNG Neurology Genetics | Volume 6 Number 2 | April 2020 5

beating tremor She died at the age of 61 years and her brainautopsy was obtained

Genetic studiesWhole exome sequence data were obtained from the individualsIII-1 and IV-1 in family A The average allele depth of coveragewas 100times with more than gt99 of the exome covered at morethan 20times We first scanned the exome data for variants in genesfor autosomal dominant SCAs no potential pathogenic variantswere present Both exomes contained a small CTG repeat ex-pansion (9CTG13CTG) in ATXN3 but the same allele wascarried by the unaffected patient (III-2) and is reported asa benign polymorphism in ClinVarWe then followed a stepwisefiltering protocol to prioritize candidate causative variants Basedon the autosomal dominant inheritance pattern of the disease inthe family and the population prevalence of 1ndash5100000 forcombined SCAs116 we selected heterozygous variants detectedin both exomes with a conservative minor allele frequencythreshold of lt00001 to avoid overfiltering Other criteria in-cluded highmoderate functional effect based on variant type(missense nonsense coding indels and splice site) and pre-diction algorithms and high evolutionary conservation

This process left 4 candidate variants (table e-1 linkslwwcomNXGA222) of which the missense variant in STUB1 was themost compelling The variant in exon 1 c158TgtC pIle53Thr(RefSeq NM_005861) affects an evolutionarily conserved resi-due (GERP366 phastCons 1) and is predicted to be deleteriousby SIFT (0001) PolyPhen2 (100) and CADD (241) The

variant is not present in the gnomAD database STUB1 has beenassociatedwith SCAR16 an autosomal recessive SCA217 Sangersequencing confirmed the variant and identified it in all 4 affectedpatients and not in the unaffected one None of the other 3prioritized candidate variants showed complete cosegregationwith the disease in family A In family B clinical exome se-quencing reported a heterozygous STUB1 variant of uncertainsignificance c111CgtG pThe37Leu in the proband The variantis located in a highly conserved residue (GERP 35 phastCons1) and is predicted to be disease causing by SIFT (001) Poly-Phen2 (100) andCADD(247) Furthermore the variant is notpresent in the gnomAD database This variant was not detectedby targeted sequencing in the unaffected sibling Other membersof these 2 families were not available for testing

We performed a literature search using PubMed and multiplepublic variant databases including ClinVar MARRVEL18

Varsome19 and VarCards20 for variants reported in STUB1(figure 3) Considering the phenotypes evidence for cose-gregation and predicted or experimentally shown effect onprotein function we found 26 homozygous or compoundheterozygous-likely pathogenic variants all of which werereported in SCAR16 cases none of these STUB1 variants werereported in autosomal dominant SCAMost of these mutationsare included in a recent report on SCAR1621 While we werepreparing this manuscript one case with SCA and a frame-shiftmutation pL275Dfs16 and 2 withmissensemutations pG33Sand pP228S in STUB1 were reported56 This deletion andpP228S are located in the U-box domain whereas the 2

Figure 2 Neuroimaging

(A) MRI of patient III-1 in family A at 53 years ofage showing marked midline cerebellar atrophymildly enlarged lateral ventricle and normalcorpus callosum (B) MRI of patient A IV-1 at 32years of age showing marked midline cerebellaratrophy before the onset of ataxia but havingcognitive disability and autism spectrum disor-der (C and D) MRI of patient III-2 in family B at 48years of age showing midline (C) and lateral (D)cerebellar atrophy

6 Neurology Genetics | Volume 6 Number 2 | April 2020 NeurologyorgNG

variants in families A and B are both in the N-terminal tetra-tricopeptide repeat domain (also pG33S figure 3)

Neuropathologic studies

Gross findings

Patient A II-2The brain only showed atrophy of the superior vermis anddorsal region of the cerebellar hemisphere No other signifi-cant pathologic findings were noted

Patient A III-1The 1120 g (fresh) brain had mild cortical atrophy involvingfrontal lobes without significant temporal parietal or occipitalcortical atrophy On cut sections the lateral ventricles wereenlarged bilaterally and the hippocampus was moderatelyatrophic The cerebellar vermis was small and firm and thedentate nucleus appeared mildly atrophic on cut sections

Patient A IV-1The 939 g (fresh) brain had moderate cortical atrophy andsevere cerebellar atrophy (figure e-1 linkslwwcomNXG

A221) The cerebellar atrophy globally included the cortexwith marked thinning of the folia but the deep cerebellarnuclei appeared unremarkable (figure e-1)

Patient B III-2The 1040 g (fresh) brain had no significant cortical atrophyhowever the cerebellum was markedly atrophic in a diffuseglobal pattern In addition the basis pontis was mildlyflattened

Histopathologic findingsEach case in family A showed similar histologic findings inthe cerebellum (figure 4) HampELFB-stained slides showthinning of the cerebellar folia with marked loss of PCsBielschowsky silver stain demonstrates empty baskets inassociation with the loss of PCs and there is reduced cal-bindin immunohistochemistry There is also increasedastrogliosis and Bergmann gliosis highlighted on the GFAPimmunostain Scattered ubiquitinated inclusions are pres-ent but no p62 inclusions are identified Notably therewas no evidence of TDP-43 or alpha-synuclein-positiveinclusions

Figure 3 Ataxia-related variants in STUB1

(A) STUB1 gene showing reported variants associated with autosomal dominant and recessive ataxias and the corresponding locations in the protein Colorsindicate the TPR (turquoise) coiled-coil (purple) and E3 ubiquitin ligase (U-box) domains in STUB1 Bold = heterozygous autosomal dominant variantsreported by Genis et al5 andDeMichele et al6 and in this report (in red) Arrow = an intronicmutation at the donor splice site of exon 4 (B) Diagramdepicts thelocation of the pIle53Thr (red amino acid) and pPhe37Leu (yellow amino acid) missense variants within a 3-D model of a STUB1 homodimer (the functionalisoform) STUB1 was modeled with PyMOL (pymolorg) using the data from the protein data bank (rcsborg PDB ID2C2L) TPR = tetratricopeptide repeat

NeurologyorgNG Neurology Genetics | Volume 6 Number 2 | April 2020 7

In patient A II-2 other neuropathologic findings includingneurofibrillary tangles present within several regions of thehippocampus including CA2 and subiculum in addition to thetransentorhinal cortex (Braak III) without evidence of beta-amyloid pathology (Thal 0 Consortium to Establish a Registryfor Alzheimerrsquos Disease [CERDAD] score absent) In patient AIII-1 scattered neurofibrillary tangles were limited to the pre-alpha cells of the transentorhinal cortex (Braak I) with patchydiffuse neocortical amyloid plaques (Thal 1) and no neuriticplaques were identified (CERAD absent) In patient A IV-1there are rare neurofibrillary tangles limited to the pre-alpha cellsof the transentorhinal cortex without the evidence of beta-amyloid pathology (Braak I Thal 0 CERAD absent) Therewere also patchy white matter lesions located in the subcorticalwhite matter corpus callosum anterior commissure and theinternal capsule characterized by a loss of myelinated axonsmost consistent with acutemicroinfarcts No pathologic findingswere noted in the basal ganglia in any of the cases in this family

In patient B III-2 HampE-stained slides show diffuse bilateralPC loss and cerebellar cortical atrophy Bielschowsky stainsconfirm PC loss highlighted by diffuse empty baskets andrare torpedo axons Calbindin immunostain showed markedloss of fibers and GFAP immunostain highlighted Bergman

and astrogliosis Scattered ubiquitin-positive inclusions arenoted but no p62- TDP-43-positive or alpha-synuclein-positive inclusions are identified Other neuropathologicchanges include sparse neuritic plaques in the neocortex(CERAD sparse) and diffuse amyloid plaques present inisocortex hippocampus and striatum (Thal 3) Neurofi-brillary tangles are limited to the pre-alpha cells of thetransentorhinal cortex (Braak I) No pathologic changeswere noted in the basal ganglia

STUB1 confocal microscopy findingsThere are at least 29 previously reported pathogenic variants inSTUB1 (figure 3) 3 dominant and 26 recessive some of whichdestabilize the protein in vitro3 but currently there are noreported data regarding the effects of mutant STUB1 proteinexpression in the cerebellum of an individual harboring anataxia-related STUB1 variant To address this question wecarried out confocal microscopy using the rare neuropathologiccerebellum specimens from our 4 autopsied cases (II-2 III-1and IV-1 in family A and III-2 in family B)

Figure 5A shows results from 2 normal controls (andashh) wherethe STUB1 expression in the cerebellar molecular layer wasexpressed prominently in PCs Additional information about

Figure 4 Microscopic neuropathology

Microscopic sections of the patients from both families showing marked cerebellar atrophy with thinning of the folia (HampELFB low magnification) andPurkinje cell (PC) loss (HampELFB high magnification) The loss of PCs is also highlighted by the empty baskets noted on Bielschowsky silver stain and by thesevere reduction in calbindin-positive fibers (calbindin and GFAP immunostaining available on request) HampE = hematoxylin and eosin

8 Neurology Genetics | Volume 6 Number 2 | April 2020 NeurologyorgNG

the localization of STUB1 was revealed by coimmunostainingcalbindin and the neuronal glutamate transporter EAAT4which is known to be expressed virtually exclusively in PCplasma membranes2223 EAAT4 immunostaining was carried

out to augment the calbindin staining because EAAT4 morecomprehensively labels distal dendritic compartments of thePCs (compare b and c in figure 5A) In a normal controlSTUB1 expression was polarized in PCs with the most

Figure 5 Loss of polarized STUB1 expression in Purkinje cells in patients with STUB1-cerebellar ataxia

Immunostaining was performed withantibodies to STUB1 (pseudocoloredpurple) EAAT4 (green) and calbindin(red) and all scanning acquisition andpostprocessing parameters were car-ried out identically among the casesabout the controls in each panel In 3different normal control individuals(AandashAd BandashBd CandashCd) STUB1 im-munoreactivity was uniformly localizedprimarily in PC cell bodies and proximaldendrites with little expression in distalPC dendritic arbors (A and B) Family Awith STUB1-Ile53Thr Loss of STUB1polarization results in aberrant ex-pression in distal PC dendritic arborsand cell bodies in patients III-1 (AendashAh)IV-1 (BendashBh) and II-2 (BindashBl) Scalebars = 100 μm (C) Family B with STUB1-Phe37Leu In individual III-2 STUB1 wasaberrantly expressed in PC distalarbors (CendashCh) Scale bars = 50 μm

NeurologyorgNG Neurology Genetics | Volume 6 Number 2 | April 2020 9

prominent expression confined to cell bodies and proximaldendrites (somatodendritic) and much less in the distal den-dritic compartments that project prominently into the cere-bellar molecular layer Note that although EAAT4immunostaining (figure 5Ab) confirmed that the image fieldincluded extensive normal-appearing PC dendritic arborsSTUB1 expression was restricted mostly to the PC cell bodiesand proximal dendrites (figure 5Aa) In marked contrast tothis STUB1 immunostaining from patient III-1 in family Awith Ile53Thr-STUB1 (figure 5Aindashl) revealed an apparent lossof normal STUB1 polarization that was evidenced by expres-sion throughout the distal PC arbors in addition to the soma-todendritic compartments As with patient A III-1 STUB1immunoreactivity was aberrantly expressed in distal PC den-dritic processes of patient A IV-1 (figure 5Bendashh) and A II-2(figure 5Bindashl) Inspection of the cerebellum from family Bpatient III-2 with Phe37Leu-STUB1 (figure 5Cendashh) alsorevealed the same pattern of aberrant distal PC arbor STUB1expression

To address the possibility that loss of polarized PC STUB1expression could be due to nonspecific neurodegenerative

processes we also examined STUB1 expression in SCA5SCA3 and SCA-7 In SCA5 (figure 6 EndashH) and SCA3(figure 6 IndashL) STUB1 immunostaining was not differentfrom the control (figure 6 AndashD) These findings suggest thataberrant STUB1 expression in PCs is not mediated solely bynonspecific PC degeneration However in the SCA7 case(figure 6 MndashP) STUB1 appeared mislocalized in distaldendritic arbors Thus it is unlikely that PC STUB1 mis-localization is mediated selectively by these 2 dominantlyinherited STUB1 variants

DiscussionSTUB1was previously associated with SCAR16 an autosomalrecessive ataxia3 Recently 3 families with ataxia segregatingheterozygous frameshift (pL275Dfs16) or a missense(pGly33Ser or pPro228Ser) variant in STUB1 have beenreported but neuropathology was not included56 The 2 newfamilies we describe herein confirm that heterozygous variantsin STUB1 can cause autosomal dominant hereditary cere-bellar ataxia expand the associated pathogenic missense

Figure 6 STUB1 expression pattern in Purkinje cells in a number of non-STUB1-associated ataxias and cerebellardegeneration

In a normal individual (AndashD) STUB1immunoreactivity was expressedmostly in PC cell bodies and proximaldendrites (pseudocolored purple)Calbindin (red) and EAAT4 (green)immunostained PC bodies and den-drites STUB1 localization appearednormal in PCs from SCA5 (EndashH) andSCA3 (IndashL) In an SCA7 case STUB1expression was aberrantly localizedin distal PC dendritic arbors (MndashP)Scale bars = 100 μm

10 Neurology Genetics | Volume 6 Number 2 | April 2020 NeurologyorgNG

variants broaden the age at onset range and neuro-developmental manifestations to include childhood autismspectrum disorder document that the cerebellum is theprominent target of the pathologic process and provide evi-dence that there is a change in cellular distribution of STUB1in PCs Taken together these 5 families document thatSTUB1-related dominant ataxia is commonly associated withcognitive and behavioral disturbances that may precede theataxia by years

With advances in sequencing and improvements in variantinterpretation techniques the tremendous heterogeneity ofneurogenetic disorders is more evident and it is increasinglyapparent that genes once associated only with one form ofinheritance are in fact capable of causing both recessive anddominant forms24ndash27 The nomenclature that assigns a se-quential number to each gene in a disease category providesno clarifying information and has limited clinical or researchutility As proposed regarding the nomenclature of re-cessive cerebellar ataxia28 and other genetic movementdisorders29 we suggest ATX-STUB1 and SCA-STUB1 toreplace SCAR16 and SCA48

The features of the recessive and dominant forms of SCA-STUB1 ataxia overlap including progressive cognitiveimpairment However in the recessive form the behavioraldeficit is usually mild and the onset of ataxia is usually inearly childhood to the mid-20s23031 Additional features ofthe recessive formmay include spasticity of the lower limbsmild peripheral sensory neuropathy and hypogonado-tropic hypogonadism303233 As with other dominant dis-orders clinical manifestations and age at onset are variableeven within families The mild parkinsonian features notedin III-1 (family A) and the wing beating-like tremor seenlate in the disease in III-2 (family B) are apparently addi-tional features that may occur in the dominant form of thissyndrome

A role for the cerebellum in autism has been previously sug-gested and both decreased cerebellar vermis volume and PCdensity have been observed34ndash36 The single case of autismspectrum disorder in the present family does not prove anassociation with STUB1 mutations but is noteworthy andcontinued search for additional examples in other families It isof interest that this family memberrsquos MRI showed cerebellaratrophy at the time of her diagnosis of autism but before theonset of ataxia and cognitive decline

The neuropathologic findings in the 4 brains from the 2families reported here are remarkably similar in the prom-inent cerebellar atrophy with the loss of PCs Our casessupport the direct effect of cerebellar pathology on thecognitivebehavioral features of SCA-STUB1 because cere-bellar atrophy was found on imaging when the cognitivebehavioral abnormality was evident before the clinical signsof ataxia were displayed and because no significant brainpathology outside the cerebellum was identified on autopsy

This is consistent with the hypothesis that the cerebellumparticipates in cognitive processing and emotionalcontrol3738 The only previous neuropathologic descriptionassociated with SCA-STUB1 disease is in an autosomal re-cessive case that also showed marked PC loss4 CHIP(STUB1) immunostaining labeled primarily cytoplasm inthe neurons of the paraventricular nuclei of the hypothala-mus and nuclear staining of pyramidal neurons of the medial-entorhinal cortex No CHIP staining of the cerebellum wasreported The authors speculated that the involvement offrontal and temporal cortex was likely related to the dementiathat developed in the later stages of the disease The remarkablylow total brain weight in our patient A IV-1 suggests there maybe abnormalities in the cerebral cortex beyond what we wereable to detect microscopically and may be related to thehypometabolism on fluorodeoxyglucose-PET studies of thecerebellum striatum and cerebral cortex reported6

The CHIP ubiquitin ligase encoded by STUB1 functions asa homodimer39 A number of variants responsible for therecessive form of ATX-STUB1 have been shown to reduceSTUB1 protein stability in vitro suggesting that thesemutations may lead to lower steady-state STUB1 expressionlevels3 yet the carriers remain unaffected Therefore hap-loinsufficiency and dominant negative mechanisms seemunlikely for the dominant presentation The autosomaldominant missense and frameshift variants may have a toxicgain of function effect56

In support of a toxic gain of function we found that theintracellular location of STUB1 protein in PCs is altered bythe missense variants In PCs STUB1 is normally polar-ized with the most prominent expression in somatoden-dritic compartments and lower expression in the distaldendritic arbors that extend into the cerebellar molecularlayer The molecular layer is filled with a dense network ofEAAT4-positive ldquoknotted lace-likerdquo PC arbors that is quitelarge compared with the PC somatodendritic compart-ments hence further emphasizing the highly polarizednature of normal STUB1 protein expression in PCs In thepIle53Thr and pPhe37Leu cases in this study STUB1appeared to lose somatodendritic polarization allowingSTUB1 to localize in distal PC arbors and cell bodies Thefaint cytoplasmic staining of STUB1 and extension intodendrites and axons were also observed in the cortex of thepatient with recessive ATX-STUB14 however the cere-bellum was not evaluated for STUB1 in that study Addi-tional functional studies of the pathogenic variantsresponsible for these ataxias may clarify the biochemicalconsequences of this location shift

The involvement of STUB1 in disease extends beyond itscausative role in STUB1-ataxia The CHIP and ataxin-1 pro-teins directly interact and CHIP promotes ubiquitination ofexpanded ataxin-140 Ataxin-3 is involved in the degradation ofmisfolded chaperone substrates through its interaction withSTUB1CHIP41 Ataxin-3 is recruited to monoubiquitinated

NeurologyorgNG Neurology Genetics | Volume 6 Number 2 | April 2020 11

STUB1CHIP where it prevents further ubiquitin chain ex-tension These reports led us to examine STUB1 mislocaliza-tion in other type of SCAs The shift in subcellular localizationin our patients was not seen in SCA3 SCA5 or a nongeneticcase with chronic ischemic cerebellar injury (data not shown)Taken together these findings argue against the possibility thatSTUB1 mislocalization is mediated nonspecifically by degen-erating PCs However we also found evidence of disturbedSTUB1 polarization in the SCA7 case Therefore it is unlikelythat STUB1 mislocalization is restricted to these dominantlyexpressed STUB1mutations Detailed study of more cases andmore subtypes of SCA may shed light on the possible roleof STUB1 in a common pathway with relevance to SCAdevelopment

It is also noteworthy that the 4 brains from the 2 families wereport demonstrated no tau pathology other than low Braakstages consistent with the patientsrsquo ages This is in contrastto a report of substantial tau pathology in CHIPSTUB1knockout mice and Caenorhabditis elegans consistent withthis protein being involved in the ubiquitination of tau42

This contrast is additional evidence that the missensemutations reported here are unlikely to cause a loss offunction

In conclusion a variety of mutations in STUB1 can cause eitherautosomal recessive or autosomal dominant cerebellar ataxiaoften associated with a prominent cognitive affective syndromethat may include the autism spectrum disorder The dominantform presents with cognitive impairment at an earlier stage andataxia at a later stage in comparison to the recessive form Thebrunt of the pathologic process affects PCs where there isa mislocalization of the STUB1 protein from the cytoplasm tothe dendritic arbor Further resolution of this pathologic pro-cess will help explain the extensive variability of the hereditaryataxias

AcknowledgmentThe authors are grateful to the families whose participationmade this work possible and to JohnWolff Allison Beller LisaKeene Kim Howard and Emily Trittschuh for their excellenttechnical assistance

Study fundingSupported by NIH (1R01NS069719 U01AG005136 and5T32GM007454) and the United States (US) Department ofVeterans Affairs (Merit ReviewAward Number 101 CX001702from the Clinical Sciences RampD [CSRD] Service and RDIS0005 from the Office of Research and Development MedicalResearch Service)

DisclosureDisclosures available NeurologyorgNG

Publication historyReceived by Neurology Genetics October 16 2019 Accepted in finalform November 7 2019

References1 Bird T Hereditary ataxia overview In GeneReviews at GeneTests Medical

Genetics Information Resource [Database Online] 1993-2019 Seattle University ofWashington 2019

2 Depondt C Donatello S Simonis N et al Autosomal recessive cerebel-lar ataxia of adult onset due to STUB1 mutations Neurology 2014821749ndash1750

3 Kanack AJ Newsom OJ Scaglione KM Most mutations that cause spinocerebellarataxia autosomal recessive type 16 (SCAR16) destabilize the protein quality-controlE3 ligase CHIP J Biol Chem 20182932735ndash2743

4 Bettencourt C de Yebenes JG Lopez-Sendon JL et al Clinical and neuropathologicalfeatures of spastic ataxia in a Spanish family with novel compound heterozygousmutations in STUB1 Cerebellum 201514378ndash381

Appendix Authors

Name Location Role Contribution

Dong-HuiChen MDPhD

University ofWashington Seattle

Author Designed andconceptualized thestudy collected andanalyzed the datadrafted themanuscript forintellectual contentand edited themanuscript

CaitlinLatimerMD PhD

University ofWashington Seattle

Author Collected andanalyzed the data anddrafted themanuscript forintellectual content

MayumiYagi PhD

VA Puget SoundHealth Care SystemSeattle

Author Collected andanalyzed the data

MesakiKennethNdugga-Kabuye MD

University ofWashington Seattle

Author Collected andanalyzed the data andedited the manuscript

ElyanaHeigham

University ofWashington Seattle

Author Collected andanalyzed the data

SumanJayadev MD

University ofWashington Seattle

Author Collected the data

James SMeabonPhD

VA Puget SoundHealth Care SystemSeattle

Author Analyzed the data

ChristopherM GomezMD PhD

University of Chicago Author Collected the data

C DirkKeene MDPhD

University ofWashington Seattle

Author Collected andanalyzed the data

David GCook PhD

VA Puget SoundHealth Care SystemSeattle

Author Conceptualized thestudy collected andanalyzed the data

Wendy HRaskindMD PhD

University ofWashington Seattle

Author Designed andconceptualized thestudy drafted themanuscript forintellectual contentand edited themanuscript

Thomas DBird MD

University ofWashington VAPuget Sound HealthCare System Seattle

Author Conceptualized thestudy drafted themanuscript forintellectual contentand edited themanuscript

12 Neurology Genetics | Volume 6 Number 2 | April 2020 NeurologyorgNG

5 Genis D Ortega-Cubero S San Nicolas H et al Heterozygous STUB1 mutation causesfamilial ataxia with cognitive affective syndrome (SCA48) Neurology 201891e1988ndashe1998

6 De Michele G Lieto M Galatolo D et al Spinocerebellar ataxia 48 presenting withataxia associated with cognitive psychiatric and extrapyramidal features a report oftwo Italian families Parkinsonism Relat Disord 20196591ndash96

7 McDonough H Patterson C CHIP a link between the chaperone and proteasomesystems Cell Stress Chaperones 20038303ndash308

8 Chen D-H Below JE Shimamura A et al Ataxia-pancytopenia syndrome is caused bymissense mutations in SAMD9L Am J Hum Genet 2016981146ndash1158

9 Davydov EV Goode DL Sirota M Cooper GM Sidow A Batzoglou S Identifyinga high fraction of the human genome to be under selective constraint using GERP++PLoS Comput Biol 20106e1001025

10 Ng PC Henikoff S SIFT predicting amino acid changes that affect protein functionNucleic Acids Res 2003313812ndash3814

11 Sunyaev S Ramensky V Koch I Lathe W III Kondrashov AS Bork P Prediction ofdeleterious human alleles Hum Mol Genet 200110591ndash597

12 Ramensky V Bork P Sunyaev S Human non-synonymous SNPs server and surveyNucleic Acids Res 2002303894ndash3900

13 Kircher M Witten DM Jain P OrsquoRoak BJ Cooper GM Shendure J A generalframework for estimating the relative pathogenicity of human genetic variants NatGenet 201446310ndash315

14 Chen YZ Matsushita MM Robertson P et al Autosomal dominant familial dyski-nesia and facial myokymia single exome sequencing identifies a mutation in adenylylcyclase 5 Arch Neurol 201269630ndash635

15 Wechsler D Wechsler Adult Intelligence ScalemdashRevised (WAIS-R) San AntonioThe Psychological Corporation 1981

16 Ruano L Melo C SilvaMC Coutinho P The global epidemiology of hereditary ataxiaand spastic paraplegia a systematic review of prevalence studies Neuroepidemiology201442174ndash183

17 Pakdaman Y Sanchez-GuixeM Kleppe R et al In vitro characterization of six STUB1variants in spinocerebellar ataxia 16 reveals altered structural properties for theencoded CHIP proteins Biosci Rep 201737BSR20170251

18 Wang J Al-Ouran R Hu Y et al MARRVEL integration of human and modelorganism genetic resources to facilitate functional annotation of the human genomeAm J Hum Genet 2017100843ndash853

19 Kopanos C Tsiolkas V Kouris A et al VarSome the human genomic variant searchengine Bioinformatics 2018351978ndash1980

20 Li J Shi L Zhang K et al VarCards an integrated genetic and clinical databasefor coding variants in the human genome Nucleic Acids Res 201846D1039ndashD1048

21 Turkgenc B Sanlidag B Eker A et al STUB1 polyadenylation signal variant AACAAAdoes not affect polyadenylation but decreases STUB1 translation causing SCAR16Hum Mutat 2018391344ndash1348

22 Bar-Peled O Ben-Hur H Biegon A et al Distribution of glutamate transportersubtypes during human brain development J Neurochem 1997692571ndash2580

23 Dehnes Y Chaudhry FA Ullensvang K Lehre KP Storm-Mathisen J Danbolt NCThe glutamate transporter EAAT4 in rat cerebellar Purkinje cells a glutamate-gatedchloride channel concentrated near the synapse in parts of the dendritic membranefacing astroglia J Neurosci 1998183606ndash3619

24 Chen DH Meneret A Friedman JR et al ADCY5-related dyskinesia broaderspectrum and genotype-phenotype correlations Neurology 2015852026ndash2035

25 Barrett MJ Williams ES Chambers C Dhamija R Autosomal recessive inheritance ofADCY5-related generalized dystonia and myoclonus Neurol Genet 20173193

26 Lise S Clarkson Y Perkins E et al Recessive mutations in SPTBN2 implicate beta-IIIspectrin in both cognitive and motor development PLoS Genet 20128e1003074

27 Morimoto Y Yoshida S Kinoshita A et al Nonsense mutation in CFAP43 causes normal-pressure hydrocephalus with ciliary abnormalities Neurology 201992e2364ndashe2374

28 Rossi M Anheim M Durr A et al The genetic nomenclature of recessive cerebellarataxias Mov Disord 2018331056ndash1076

29 Marras C Lang A van de Warrenburg BP et al Nomenclature of genetic movementdisorders recommendations of the international Parkinson and movement disordersociety task force Mov Disord 201631436ndash457

30 Shi Y Wang J Li JD et al Identification of CHIP as a novel causative gene forautosomal recessive cerebellar ataxia PLoS One 20138e81884

31 Heimdal K Sanchez-Guixe M Aukrust I et al STUB1 mutations in autosomalrecessive ataxiasmdashevidence for mutation-specific clinical heterogeneity Orphanet JRare Dis 20149146

32 Shi CH Schisler JC Rubel CE et al Ataxia and hypogonadism caused by the loss ofubiquitin ligase activity of the U box protein CHIP Hum Mol Genet 2014231013ndash1024

33 Synofzik M Schule R Schulze M et al Phenotype and frequency of STUB1 muta-tions next-generation screenings in Caucasian ataxia and spastic paraplegia cohortsOrphanet J Rare Dis 2014957

34 Webb SJ Sparks BF Friedman SD et al Cerebellar vermal volumes and behavioralcorrelates in children with autism spectrum disorder Psychiatry Res 200917261ndash67

35 Skefos J Cummings C Enzer K et al Regional alterations in purkinje cell density inpatients with autism PLoS One 20149e81255

36 Wang SS Kloth AD Badura A The cerebellum sensitive periods and autism Neuron201483518ndash532

37 Schmahmann JD The cerebellum and cognition Neurosci Lett 201968862ndash7538 Liang KJ Carlson ES Resistance vulnerability and resilience a review of the cognitive

cerebellum in aging and neurodegenerative diseases Neurobiol LearnMem 2019 doi101016jnlm201901004 Epub 2019 Jan 7

39 Nikolay RWiederkehr T RistW Kramer GMayerMP Bukau B Dimerization of thehuman E3 ligase CHIP via a coiled-coil domain is essential for its activity J Biol Chem20042792673ndash2678

40 Al-Ramahi I Lam YC Chen HK et al CHIP protects from the neurotoxicity ofexpanded and wild-type ataxin-1 and promotes their ubiquitination and degradationJ Biol Chem 200628126714ndash26724

41 Scaglione KM Zavodszky E Todi SV et al Ube2w and ataxin-3 coordinately regulatethe ubiquitin ligase CHIP Mol Cell 201143599ndash612

42 Dickey CA Yue M Lin WL et al Deletion of the ubiquitin ligase CHIP leads to theaccumulation but not the aggregation of both endogenous phospho- and caspase-3-cleaved tau species J Neurosci 2006266985ndash6996

43 Wechsler DWMS-RWechsler Memory ScalemdashRevised San Antonio PsychologicalCorp Harcourt Brace Jovanovich 1987

44 King FW Bird TD Trail making test norms for college males and relationship toscholastic aptitude Percept Mot Skills 196521199ndash206

45 Woodcock RW Johnson B Woodcock-Johnson Psycho-Educational BatteryndashRevised Rolling Meadows IL Riverside 1989

46 Woodcock R Johnson B Woodcock-Johnson Psychoeducational Battery-RevisedTests of Achievement Chicago Riverside Publishing 1990

47 Sheslow D Adams WWide Range Assessment of Memory and Learning (WRAML)Wilmington DE Jastak 1990

48 GrantDA Berg E A behavioral analysis of degree of reinforcement and ease of shifting tonew responses in Weigl-type card-sorting problem J Exp Psychol 194838404ndash411

49 Hooper H Hooper Visual Organization Test (VOT) Los Angeles Western Psy-chological Services 1983

50 Wiens AN Tindall AG Crossen JR California verbal learning test a normative datastudy J Clin Neuropsychologist 1994875ndash90

NeurologyorgNG Neurology Genetics | Volume 6 Number 2 | April 2020 13

DOI 101212NXG000000000000039720206 Neurol Genet

Dong-Hui Chen Caitlin Latimer Mayumi Yagi et al mislocalization

missense variants cause ataxia cognitive decline and STUB1STUB1Heterozygous

This information is current as of February 20 2020

ServicesUpdated Information amp

httpngneurologyorgcontent62e397fullhtmlincluding high resolution figures can be found at

References httpngneurologyorgcontent62e397fullhtmlref-list-1

This article cites 43 articles 7 of which you can access for free at

Subspecialty Collections

httpngneurologyorgcgicollectionspinocerebellar_ataxiaSpinocerebellar ataxia

httpngneurologyorgcgicollectiongait_disorders_ataxiaGait disordersataxiafollowing collection(s) This article along with others on similar topics appears in the

Permissions amp Licensing

httpngneurologyorgmiscaboutxhtmlpermissionsits entirety can be found online atInformation about reproducing this article in parts (figurestables) or in

Reprints

httpngneurologyorgmiscaddirxhtmlreprintsusInformation about ordering reprints can be found online

reserved Online ISSN 2376-7839Published by Wolters Kluwer Health Inc on behalf of the American Academy of Neurology All rightsan open-access online-only continuous publication journal Copyright Copyright copy 2020 The Author(s)

is an official journal of the American Academy of Neurology Published since April 2015 it isNeurol Genet