Evidence that Microtubules Do Not Mediate Opsin Vesicle Transport ...
Inner retinal and extraretinal photoreceptor up-dates: Isolation and characterisation of VA opsin in...
1
Society for Experimental Biology Annual Main Meeting 6th – 10th July 2008, Marseille, France C2 — CIRCADIAN CLOCKS C2.1 Inner retinal and extraretinal photoreceptor up-dates: Isolation and characterisation of VA opsin in Xenopus and the chicken R. Foster (University of Oxford); S. Pires (University of Oxford); M. Turton (University of Oxford); S. Peirson (University of Oxford); L. Zheng (University of Oxford); J. Garcia-Fernández (University of Oviedo); M. Hankins (University of Oxford); S. Halford (University of Oxford) Vertebrate Ancient (VA) opsin was first isolated from Atlantic salmon ocular cDNA in 1997. Salmon VA-opsin shares 37–41% amino acid identity with the classical retinal opsins and 42% identity with chicken P-opsin. Furthermore, Salmon VA-opsin forms a functional photopigment when expressed in vitro and reconstituted with 11-cis-retinal. Significantly, VA- opsin is expressed in a subset of horizontal and ganglion cells in the retina and electrophysiological recordings have explored the photoreceptor capacity of these retinal neurones. Subsequent in situ hybridisation studies demonstrated that Salmon VA-opsin is also expressed in the pineal organ and habenular region of the brain, both structures either known to be or implicated in photoreception. Similar findings have been reported in many fish species including the common carp and zebrafish. Despite the isolation of a VA-opsin homologue from the marine lamprey, all attempts to isolate VA-opsin from other vertebrate classes failed. This failure led to the suggestion that the VA-opsins were ancestral to the tetrapod P-opsins and that direct homologues of VA-opsins would not be found in terrestrial vertebrates. This assumption was incorrect. The presentation will describe the isolation, characterisation, functional expression and distribution of VA-opsins from both Xenopus and the chicken. In the chicken at least, this discovery provides some insight as to how “deep brain photoreceptors” might regulate photoperiodic and circadian responses to light. doi:10.1016/j.cbpa.2008.04.374 C2.2 Neurobiology of food-entrainable circadian rhythms in mammals R. Mistlberger (Simon Fraser University) Circadian rhythms in mammals are regulated by a light- entrainable circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). In nocturnal rodents, SCN output suppresses activity and promotes sleep during the day, and promotes activity, wake and feeding at night. If food is restricted to one daytime meal, circadian oscillators outside of the SCN are engaged that generate a daily rhythm of food anticipatory activity, overriding SCN-mediated behavioral suppression. The properties of food-entrainable circadian rhythms have been well-characterized, but neurobiological analysis has been slow until recently. Progress has been catalysed by the discovery that circadian clock genes at the core of the SCN pacemaker also exhibit circadian rhythms of expression in numerous other brain regions and peripheral organs, and that in most cases the phase of these rhythms is set by mealtime. Knockout of the Per2 gene in mice confirms a role for these clock genes in food-entrainable behavioral rhythms. The site of oscillators critical for food-entrainable behavioral rhythms remains an open question. Lesion experiments have ruled out numerous areas as necessary, but controversy has emerged over the role of food-entrainable oscillators in the hypothalamic dorsomedial nucleus (DMH). One lab has reported severe attenuation or loss of food-anticipatory rhythms after neurotoxic ablation of DMH cell bodies (Gooley et al., 2006), while two labs (Landry et al., 2006, 2007; Moriya et al., 2007) report normal food-entrainable rhythms after radiofrequency ablation of this region. Discrepancies may be attributable to lesion and behavior methods, and can be accom- modated by assigning the DMH a role inhibiting SCN-dependent behavioral suppression. doi:10.1016/j.cbpa.2008.04.375 C2.3 A genome-wide RNAi screen for novel components of the mammalian circadian clock A. Kramer, B. Maier, S. Wendt (Charité Universitätsmedizin Berlin) Comparative Biochemistry and Physiology, Part A 150 (2008) S148–S154 Contents lists available at ScienceDirect Comparative Biochemistry and Physiology, Part A journal homepage: www.elsevier.com/locate/cbpa
Transcript of Inner retinal and extraretinal photoreceptor up-dates: Isolation and characterisation of VA opsin in...
Society for Experimental Biology Annual Main Meeting6th – 10th July 2008, Marseille, France
C2 — CIRCADIAN CLOCKS
C2.1Inner retinal and extraretinal photoreceptor up-dates: Isolationand characterisation of VA opsin in Xenopus and the chicken
R. Foster (University of Oxford); S. Pires (University of Oxford); M.Turton (University of Oxford); S. Peirson (University of Oxford); L. Zheng(University of Oxford); J. Garcia-Fernández (University of Oviedo); M.Hankins (University of Oxford); S. Halford (University of Oxford)
Vertebrate Ancient (VA) opsin was first isolated from Atlantic salmonocular cDNA in 1997. Salmon VA-opsin shares 37–41% amino acid identitywith the classical retinal opsins and 42% identity with chicken P-opsin.Furthermore, Salmon VA-opsin forms a functional photopigment whenexpressed in vitro and reconstituted with 11-cis-retinal. Significantly, VA-opsin is expressed in a subset of horizontal and ganglion cells in the retinaand electrophysiological recordings have explored the photoreceptorcapacity of these retinal neurones. Subsequent in situhybridisation studiesdemonstrated that Salmon VA-opsin is also expressed in the pineal organand habenular region of the brain, both structures either known to be orimplicated inphotoreception. Similar findingshavebeen reported inmanyfish species including the common carp and zebrafish. Despite theisolation of a VA-opsin homologue from themarine lamprey, all attemptsto isolate VA-opsin from other vertebrate classes failed. This failure led tothe suggestion that the VA-opsinswere ancestral to the tetrapod P-opsinsand that direct homologues of VA-opsinswould not be found in terrestrialvertebrates. This assumptionwas incorrect. The presentationwill describethe isolation, characterisation, functional expression and distribution ofVA-opsins from bothXenopus and the chicken. In the chicken at least, thisdiscovery provides some insight as to how “deep brain photoreceptors”might regulate photoperiodic and circadian responses to light.
doi:10.1016/j.cbpa.2008.04.374
C2.2Neurobiology of food-entrainable circadian rhythms in mammals
R. Mistlberger (Simon Fraser University)
Circadian rhythms in mammals are regulated by a light-entrainable circadian pacemaker located in the hypothalamicsuprachiasmatic nucleus (SCN). In nocturnal rodents, SCN outputsuppresses activity and promotes sleep during the day, andpromotes activity, wake and feeding at night. If food is restrictedto one daytime meal, circadian oscillators outside of the SCN areengaged that generate a daily rhythm of food anticipatory activity,overriding SCN-mediated behavioral suppression. The properties offood-entrainable circadian rhythms have been well-characterized,but neurobiological analysis has been slow until recently. Progresshas been catalysed by the discovery that circadian clock genes at thecore of the SCN pacemaker also exhibit circadian rhythms ofexpression in numerous other brain regions and peripheral organs,and that in most cases the phase of these rhythms is set bymealtime. Knockout of the Per2 gene in mice confirms a role forthese clock genes in food-entrainable behavioral rhythms. The site ofoscillators critical for food-entrainable behavioral rhythms remainsan open question. Lesion experiments have ruled out numerousareas as necessary, but controversy has emerged over the role offood-entrainable oscillators in the hypothalamic dorsomedialnucleus (DMH). One lab has reported severe attenuation or loss offood-anticipatory rhythms after neurotoxic ablation of DMH cellbodies (Gooley et al., 2006), while two labs (Landry et al., 2006,2007; Moriya et al., 2007) report normal food-entrainable rhythmsafter radiofrequency ablation of this region. Discrepancies may beattributable to lesion and behavior methods, and can be accom-modated by assigning the DMH a role inhibiting SCN-dependentbehavioral suppression.
doi:10.1016/j.cbpa.2008.04.375
C2.3A genome-wide RNAi screen for novel components of themammalian circadian clock
A. Kramer, B. Maier, S. Wendt (Charité Universitätsmedizin Berlin)
Comparative Biochemistry and Physiology, Part A 150 (2008) S148–S154
Contents lists available at ScienceDirect
Comparative Biochemistry and Physiology, Part A
j ourna l homepage: www.e lsev ie r.com/ locate /cbpa
