Erik HaleyChronic Diseases

4/1/13

Genomics

GenomicsPublic Health Genomics focuses on the

application of genomic research to health benefits.

Genomics plays a role in 9 of the 10 leading causes of death in the US- most in cancer or heart disease

One of the main risks for heart disease is familial hypercholesterolemia – a family condition that results in high levels of bad cholesterol

Genetics of HumansHumans have approximately 29,000 genes

but this only amounts to about 2% of the genome

The remaining DNA is either non-coding introns, transposable elements, regulatory sequences or a variety of other elements

Of the known proteins in the human body, only half have a well known function

EpigeneticsEpigenetics involves looking at environmental

or developmental factors that influence gene expression

Methods of modifying DNA expression include histone modification, methylation, non-coding RNA interference – all of which help reprogram the genome during embryogenesis

This reprogramming is essential for cell differentiation – understanding how it occurs can allow deprogramming

Family HistoryPeople who have a family member with a

chronic health condition have an increased risk of developing the disease

A good record of family history would contain three generations of family members, ages and causes of death and age of diagnosis for any chronic diseases

Family Health Portrait Website: https://familyhistory.hhs.gov/fhh-web/home.action

Family History Data

Genetic TestingCurrently, there are over 2000 genetic

tests available at clinical settings. Most diagnose rare genetic disorders such as duchenne muscular dystrophy.

Research is trying to develop tests that will measure an individual’s risk factors for chronic diseases or response to medicine

Genetic Testing- DrawbacksMost genetic testing available now has limited

use due to the genetic components for many chronic diseases being unknown. Effective testing mostly for uncommon ailments

Many genetic tests are misused due to premature marketingEvaluation of Genomic Applications in Practice &

Prevention

Some genetic tests for hereditary cancers not effectively implemented into practice

Genetic TestingOne of the main fears of genetic testing is

the possibility of genetic discrimination

In 2008, the Genetic Information Nondisclosure Act was put into practice to prevent discrimination in both employment and insurance on the basis of genetics

The Affordable Care Act also prohibits variation of insurance premiums based on disease or genetics

Perinatal GenomicsPre-conception genetic screening is currently

available that can identify inheritable conditions before a child is conceived as well as pre-implantation genetic screening

Pre-implanatation screening can lead to parents selecting which embryo to implant via in vitro fertilization

Newborn screening involves a genetic screen for several conditions upon birth – amount varies by state

Autoimmune DiseasesMost autoimmune diseases, including

Diabetes Type 1 and Rheumatoid Arthritis, have a genetic component

Over 200 genetic loci have been linked to autoimmune disorders- no causal information has been currently identified

Most genetic factors carry moderate risk but are involved with other environmental factors- cannot use genomics alone

Gene TherapyGene therapy involves replacing a harmful

mutant gene with an accurate copy using a viral vector

Currently, no gene therapy programs have FDA approval, yet over 2000 clinical trials were performed within the last 5 years

Additional use for gene therapy is to treat cancer by having an oncolytic virus insert a sequence that leads to cell death

Gene Therapy

Gene Therapy TechniquesOne method of gene therapy is to insert

proper alleles to replace mutant forms – nonsense mutants (early stop codon) can also be repaired by inserting a random amino acid into the mutation site

Alternative methods include using miRNA to silence certain genes by preventing transcription or changing splice sites of the pre-messenger RNA

Gene Therapy- DrawbacksOne of the drawbacks of using viral vectors

is non-specific insertion into a cell – one 2002 case had 25% insert before a proto-oncogene leading to leukemia

Many cancer cells contain an over-expression of surface proteins found on normal cells – normal cells can uptake oncolytic viruses leading to tissue death

RegenerationGenetic analysis of newts and zebrafish

determined that they are able to re-grow limbs by using highly proliferative muscle, cartilage, neural cells

In humans, Rb protein and ARF prevent muscle cells from continuing mitosis- RNAi was shown to relieve this blockade

Risks for such a procedure involve an higher risk for cancer in cells with mitotic controls inhibited

Gene MappingThe 1000 Genomes Project published a

map of the variation in the human genome to show differences in disease risk and physical attributes

The project results showed that common mutations were global while rarer ones are often limited to ethnic groups/nations

Limited use – no phenotype data and population size

Health EquityOne of the hopes of genomics is that it will help

reduce the inequality of health care between racial and ethnic groups

However, genomic data has shown that there is little difference between groups compared to within groups; many variants have low risk factors

Genomic information may be helpful by providing better information about who should receive specific treatments and the size of the expected benefit

State ParticipationCurrently, only four states have health

departments that have integrated genomic knowledge into chronic disease prevention problems (MI, MN, OR, UT)

Many more states have programs to analyze newborn infants and education/awareness programs

Human Genome Epidemiology Network

OPGH established the HuGE network to help translate genetic research findings into opportunities for preventative medicine

HuGE is currently a network containing scientific research data as well as synthesis of new research projects and translation of results to humans

http://hugenavigator.net/HuGENavigator/home.do

ValueThe current benefit from genetic testing remains

small – genetics only plays a small role in many chronic diseases and few therapies exist to treat diseaseWhole genome sequencing fails to predict risk of

most common diseases

Ideally, genomics can reveal areas for possible interventions to take place – ie. B and T cell inhibitors for patients who show autoimmune disorders

Unfortunately, most genetic information about chronic diseases is very limited

CostPharmaceutical companies have used genomic

strategies for drug development but this has normally not led to late- stage development

Cost of therapeutic development has tripled since 1990 while the number of FDA approved drugs per year remains constant – many drug failures after investment

Drug companies often work with academia or government to increase effectiveness of produced drugs

Future PlansOne of the largest gaps in genetic research is

why individuals respond differently to drugs and treatment

CDC’s Office of Public Health Genetics has the following goals for 2013:1. Integrate evidence based genomic applications

into public health2. Evaluate genomic tests to identify opportunities

to improve health/transform healthcare3. Develop and provide communications about

public health genomics to various audiences

SourcesCDC Genomics:

http://www.cdc.gov/genomics/about/AAG/index.htm

Targeting DNA: http://www.commed.vcu.edu/Chronic_Disease/genetics/2013/clinicalintervention.pdf

Epigenetics: http://www.commed.vcu.edu/Chronic_Disease/genetics/whatisepigenetics.pdf

Genome Sequencing Failures: http://www.commed.vcu.edu/Chronic_Disease/genetics/2013/practicalgenetics.pdf