Risk = odds of developing illness. Both parents with the illness put you at higher risk than if single parent
Go from epidemiologic point of view to genetics Phenotypes from DSM now IV may not match what we get in genetic factors. So as Cornblatt pointed out looking at certain features of an illness like psychosis can be important
Ven diagram highlighting the likely polygenetic and multifactorial nature of these syndromes and in fact thinking of them as syndromes rather than single illnesses- One can have PSYCHOSIS with either SCZ or BP
Gene expression arrays allow you to look at function not just structure Looking at homogenous samples seems to have been helpful
One of first linkage findings pointing the scz linkage on 5 q but with none above 3 which is what look for Linkage= a particular form of a chromosome in a region is being transmitted more commonly to patients that those without the illness. AND it implies that some genetic factor within that region is likely to play a causative role in the phenotype of the illness.
These genes sit under this region so it seemed to make sense to look there, 5q region rich in interesting candidates , glutamate, gaba, 5ht YET TO DATE NO DEFINITIVE FINDINGS
Now we can map much more densely. The current standard is more than 1,000,000 snp (single nucleotide polymorphisms- meaning variation at a single base pair) This is a change from the original work that was to look at just 400 polymorphic markers (variations in sequence at larger sequences) gone away from these big pieces to be more specific which gives us much higher resolution
Also focusing on expression profiling we have begun to develop possible diagnostic tests based on gene expression profiles from leucocytes (WBC). We have been able to discriminate with nearly 99% accuracy patients with Scz , from pts with BP, from controls. In these particular 5 genes had the highest diagnostic utility . What I mean is the pattern of expression of these 5 genes provided the most information of the dx *scz vs bp vs control that the subject fell into. Interesting there were 6 subjects in this 33 who were not able to be classified and in looking at there DSM diagnosis were schizoaffective!!
CNV-copy number variants- less or more including deletions- chromo 22, 15, 1
The red lines represent the areas of deletion in each of the 13 subjects. It differs a little from subject to subject put there is some overlap.
DeCode is the Iceland group
DeCode is the Iceland group
We continue as we did from the beginning to id the genes involved and we are looking and their function as well as their structure. And in function we are going down to the proteins ( proteomics) that they code for.And we are starting to begin to think of studies of at risk and symptom treatment development and broader risk. If we could identify you as being at risk maybe we could tx you to prevent full blown illness
Understanding Genetics of Schizophrenia Carlos N. Pato, M.D. , Ph.D. Professor and Chair of Psychiatry Center for Genomic Psychiatry Keck School of Medicine University of Southern California
Lifetime Risk for Schizophrenia <ul><li>Schizophrenia </li></ul><ul><li>0.5-1.0% General Population </li></ul><ul><li>10-15% If a parent or sibling (including dizygotic twin) is schizophrenic </li></ul><ul><li>40% If both parents are schizophrenic </li></ul><ul><li>45-75% If monozygotic twin is schizophrenic </li></ul><ul><ul><li>(Same risk to children- Fisher) </li></ul></ul>
Phenotype Definition A C H D Schizophrenia Bipolar Disorder Psychosis G F E J B
Genetic Strategies <ul><li>What is linkage ? </li></ul><ul><ul><li>What is a LOD score or a NPL ? </li></ul></ul><ul><li>What is an association ? </li></ul><ul><ul><li>How to understand statistical significance. </li></ul></ul><ul><li>Candidate genes </li></ul><ul><li>Genome wide scans (genomic mapping) </li></ul><ul><li>Gene expression arrays </li></ul>
Human Mapping Assay <ul><li>A rapid, reliable and cost-effective assay for simultaneously genotyping many thousands of SNPs distributed across the genome </li></ul>Accuracy >99% AA BB AB Generic complexity reduction scheme Hybridization-based allele discrimination
Transcript probes with the highest diagnostic utility for distinguising BP, SCZ, and control subjects The expression patterns of the 35 most predictive genes correctly classified all BP and control subjects and 27 of 33 SCZ subjects.
Genome-wide Survey of CNVs Nature (2008) <ul><li>3380 patients with schizophrenia and 3139 ancestrally-matched controls </li></ul><ul><li>identified three regions </li></ul><ul><li>large (>500kb) deletions increase disease risk </li></ul><ul><li>Deletions easier to detect because of their size and replicability compared to single point mutations (single SNP) </li></ul>
Genome-wide Survey of CNVs Nature (2008) <ul><li>On chromosome 22q11.2 - identified deletions in ~0.3% of schizophrenia patients ( P =0.00056 versus controls) </li></ul><ul><li>Odds ratio = 21.6 </li></ul>
Genome-wide Survey of CNVs Chromosome 22 deletion
Genome-wide Survey of CNVs Nature (2008) <ul><li>On chromosome 15q13.2- identified deletions in ~0.3% of schizophrenia patients ( P =0.00056 versus controls) </li></ul><ul><li>Odds ratio= 17.9 </li></ul>
Genome-wide Survey of CNVs Nature (2008) <ul><li>In the same issue of Nature, a parallel paper by DeCode showed the same results </li></ul><ul><li>Extremely strong evidence for these relatively rare mutations </li></ul><ul><li>Proves the necessity for extremely large studies </li></ul>
<ul><li>Common polygenic variation contributes to risk </li></ul><ul><li>Rare variants likely to contribute to risk </li></ul><ul><li>major histocompatibility complex strongly replicated association with schizophrenia </li></ul>MHC and Common Variants Nature, 2009
Genomic Psychiatry Cohort <ul><li>We have established the goal of studying 30,000 patients and 30,000 controls </li></ul><ul><li>Schizophrenia and Bipolar disorder </li></ul><ul><li>We have begun to bring together the funding for this large-scale program </li></ul><ul><li>The NIMH launched this program with an initial $25 million dollars in grants to USC and MGH/Broad </li></ul>
Future Directions <ul><li>Gene identification </li></ul><ul><li>Gene expression </li></ul><ul><li>Proteomics </li></ul><ul><li>Treatment development </li></ul><ul><li>At risk studies- with a focus on development of pre-clinical diagnosis + treatment </li></ul>
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.