HW2: exome sequencing and complex disease Jacquemin Jonathan de Bournonville Sébastien

Table of contents Introduction Study design: o Sample selection o Sequencing strategy Variant calling Association analysis Approaches for follow-up of promising signals The role of functional assays in interpreting ESS Conclusion Exome sequencing2

Introduction Exome = only 1% of the entire genome Exome sequencing3

Introduction 4

Study design: Sample selection Objectives definition: o What kind of variants o What scale (survey range variations in individuals, find variants linked to specific trait) Samples inventory with interesting traits Focus on samples with extreme outcome o Quantitative traits → Extremes o Discrete traits → Unsuals Sequencing related individuals? Restricted geographic distribution Founder populations Exome sequencing5

Study design: Sequencing strategy High quality bases coverage Reach >20x in ~90% of the protein coding sequences Enrichment → Local variations → Aim for average depth of 60 to 80x Light coverage of the rest of the genome Exome sequencing6

Variant calling Process raw sequences into high-quality genotypes: o Cleaning the DNA o Alignment of the short sequences reads to the reference genome o Removal of the duplicate reads o Quality metrics of each sample: Exome sequencing7

Variant calling Process raw sequences into high-quality genotypes: o New quality metrics o Identification of variant sites + inspection Exome sequencing8

Variant calling Exome sequencing9

Variant calling Drawback: o Many choices for these steps -> impacts the final result Exome sequencing10

Association analysis A same variant alters different transcripts → focus on o Canonical transcript o Most deleterious transcript, etc. Should always start with single variant association tests In order to generate QQ plots and quality check o Population structure o Variants relevance Groups variants that impact gene function Exome sequencing11

Association analysis Exome sequencing12

Approaches for follow-up of promising signals Goal: identify very rare variants Different methods: o Data from other samples o Statistical imputation o Targeted sequencing Exome sequencing13

Conclusion Forward genetics Exome sequencing14

Conclusion Challenges for future: o Apply it to complex and commom diseases o Methods to combine results from different studies o New protocols or statistical methods Exome sequencing15

Thank you for listening Exome sequencing16

References savage-each-other-over-junk-dna-study-while-journalists-mis- report-the-science/#.UqXNaeLZ2os savage-each-other-over-junk-dna-study-while-journalists-mis- report-the-science/#.UqXNaeLZ2os 18+Xavier+de+Pedro+Pipeline+for+Exome+Variant+Analysis 18+Xavier+de+Pedro+Pipeline+for+Exome+Variant+Analysis ame=figures.htm ame=figures.htm sequencing sequencing Exome sequencing17