Transcript expression-aware annotation improves rare variant interpretation
Authors: Cummings Beryl B. , Karczewski Konrad J. , Kosmicki Jack A. , Seaby Eleanor G. , Watts Nicholas A. , Singer-Berk Moriel , Mudge Jonathan M. , Karjalainen Juha , Satterstrom F. Kyle , O’Donnell-Luria Anne H. , Poterba Timothy , Seed Cotton , Solomonson Matthew , Alföldi Jessica ,   Genome Aggregation Database Production Team, Alföldi Jessica , Armean Irina M. , Banks Eric , Bergelson Louis , Cibulskis Kristian , Collins Ryan L. , Connolly Kristen M. , Covarrubias Miguel , Cummings Beryl B. , Daly Mark J. , Donnelly Stacey , Farjoun Yossi , Ferriera Steven , Francioli Laurent , Gabriel Stacey , Gauthier Laura D. , Gentry Jeff , Gupta Namrata , Jeandet Thibault , Kaplan Diane , Karczewski Konrad J. , Laricchia Kristen M. , Llanwarne Christopher , Minikel Eric V. , Munshi Ruchi , Neale Benjamin M. , Novod Sam , O’Donnell-Luria Anne H. , Petrillo Nikelle , Poterba Timothy , Roazen David , Ruano-Rubio Valentin , Saltzman Andrea , Samocha Kaitlin E. , Schleicher Molly , Seed Cotton , Solomonson Matthew , Soto Jose , Tiao Grace , Tibbetts Kathleen , Tolonen Charlotte , Vittal Christopher , Wade Gordon , Wang Arcturus , Wang Qingbo , Ware James S. , Watts Nicholas A. , Weisburd Ben , Whiffin Nicola ,   Genome Aggregation Database Consortium, Salinas Carlos A. Aguilar , Ahmad Tariq , Albert Christine M. , Ardissino Diego , Atzmon Gil , Barnard John , Beaugerie Laurent , Benjamin Emelia J. , Boehnke Michael , Bonnycastle Lori L. , Bottinger Erwin P. , Bowden Donald W. , Bown Matthew J. , Chambers John C. , Chan Juliana C. , Chasman Daniel , Cho Judy , Chung Mina K. , Cohen Bruce , Correa Adolfo , Dabelea Dana , Daly Mark J. , Darbar Dawood , Duggirala Ravindranath , Dupuis Josée , Ellinor Patrick T. , Elosua Roberto , Erdmann Jeanette , Esko Tõnu , Färkkilä Martti , Florez Jose , Franke Andre , Getz Gad , Glaser Benjamin , Glatt Stephen J. , Goldstein David , Gonzalez Clicerio , Groop Leif , Haiman Christopher , Hanis Craig , Harms Matthew , Hiltunen Mikko , Holi Matti M. , Hultman Christina M. , Kallela Mikko , Kaprio Jaakko , Kathiresan Sekar , Kim Bong-Jo , Kim Young Jin , Kirov George , Kooner Jaspal , Koskinen Seppo , Krumholz Harlan M. , Kugathasan Subra , Kwak Soo Heon , Laakso Markku , Lehtimäki Terho , Loos Ruth J. F. , Lubitz Steven A. , Ma Ronald C. W. , MacArthur Daniel G. , Marrugat Jaume , Mattila Kari M. , McCarroll Steven , McCarthy Mark I. , McGovern Dermot , McPherson Ruth , Meigs James B. , Melander Olle , Metspalu Andres , Neale Benjamin M. , Nilsson Peter M. , O’Donovan Michael C. , Ongur Dost , Orozco Lorena , Owen Michael J. , Palmer Colin N. A. , Palotie Aarno , Park Kyong Soo , Pato Carlos , Pulver Ann E. , Rahman Nazneen , Remes Anne M. , Rioux John D. , Ripatti Samuli , Roden Dan M. , Saleheen Danish , Salomaa Veikko , Samani Nilesh J. , Scharf Jeremiah , Schunkert Heribert , Shoemaker Moore B. , Sklar Pamela , Soininen Hilkka , Sokol Harry , Spector Tim , Sullivan Patrick F. , Suvisaari Jaana , Tai E. Shyong , Teo Yik Ying , Tiinamaija Tuomi , Tsuang Ming , Turner Dan , Tusie-Luna Teresa , Vartiainen Erkki , Vawter Marquis P. , Ware James S. , Watkins Hugh , Weersma Rinse K. , Wessman Maija , Wilson James G. , Xavier Ramnik J. , Daly Mark J. , MacArthur Daniel G. 
Published: May 2020

The acceleration of DNA sequencing in samples from patients and population studies has resulted in extensive catalogues of human genetic variation, but the interpretation of rare genetic variants remains problematic. A notable example of this challenge is the existence of disruptive variants in dosage-sensitive disease genes, even in apparently healthy individuals. Here, by manual curation of putative loss-of-function (pLoF) variants in haploinsufficient disease genes in the Genome Aggregation Database (gnomAD)1, we show that one explanation for this paradox involves alternative splicing of mRNA, which allows exons of a gene to be expressed at varying levels across different cell types. Currently, no existing annotation tool systematically incorporates information about exon expression into the interpretation of variants. We develop a transcript-level annotation metric known as the ‘proportion expressed across transcripts’, which quantifies isoform expression for variants. We calculate this metric using 11,706 tissue samples from the Genotype Tissue Expression (GTEx) project2 and show that it can differentiate between weakly and highly evolutionarily conserved exons, a proxy for functional importance. We demonstrate that expression-based annotation selectively filters 22.8% of falsely annotated pLoF variants found in haploinsufficient disease genes in gnomAD, while removing less than 4% of high-confidence pathogenic variants in the same genes. Finally, we apply our expression filter to the analysis of de novo variants in patients with autism spectrum disorder and intellectual disability or developmental disorders to show that pLoF variants in weakly expressed regions have similar effect sizes to those of synonymous variants, whereas pLoF variants in highly expressed exons are most strongly enriched among cases. Our annotation is fast, flexible and generalizable, making it possible for any variant file to be annotated with any isoform expression dataset, and will be valuable for the genetic diagnosis of rare diseases, the analysis of rare variant burden in complex disorders, and the curation and prioritization of variants in recall-by-genotype studies.