Mi, S. | bioRxiv Science

bioRxiv2022

Polygenic Transcriptome Risk Scores Can Translate Genetic Results Between Species

Genome-wide association studies (GWAS) have implicated specific alleles and genes as risk factors for numerous complex traits. However, translating GWAS results into biologically and therapeutically meaningful discoveries remains extremely challenging. Most GWAS results identify noncoding regions of the genome, suggesting that differences in gene regulation are the major driver of trait variability. To better integrate GWAS results with gene regulatory polymorphisms, we previously developed PrediXcan (also known as "transcriptome-wide association studies" or TWAS), which maps SNPs to predicted gene expression using GWAS data. In this study, we developed RatXcan, a framework that extends this methodology to outbred heterogeneous stock (HS) rats. RatXcan accounts for the close familial relationships among HS rats by modeling the relatedness with a random effect that encodes the genetic relatedness. RatXcan also corrects for polygenic-driven inflation because of the equivalence between a relatedness random effect and the infinitesimal polygenic model. To develop RatXcan, we trained transcript predictors for 8,934 genes using reference genotype and expression data from five rat brain regions. We found that the cis genetic architecture of gene expression in both rats and humans was sparse and similar across brain tissues. We tested the association between predicted expression in rats and two example traits (body length and BMI) using phenotype and genotype data from 5,401 densely genotyped HS rats and identified a significant enrichment between the genes associated with rat and human body length and BMI. Thus, RatXcan represents a valuable tool for identifying the relationship between gene expression and phenotypes across species and paves the way to explore shared biological mechanisms of complex traits. Author SummaryUnderstanding how genetic variation affects phenotypic variation is critical to leveraging the wealth of genetic studies to make biologically and therapeutically useful discoveries. Since most of the genetic loci associated with complex diseases are regulatory in nature--meaning that they do not alter protein coding but rather subtly affect gene expression--transcriptome-wide association studies have been developed. However, these apply only to human data where large samples of unrelated individuals are available. For animal models, relatedness is much higher, causing higher false-positive rates. We propose a computationally efficient method to address this problem and find shared biology between humans and rats. Taken together, our development paves the way to further explore shared biological mechanisms of complex traits across species.

genomics↗

bioRxiv2020

Vulnerability of ARID1A deficient cancer cells to pyrimidine synthesis blockade

Here we report the discovery and preclinical validation of a novel precision medicine strategy for ARID1A-mutated cancer. Unbiased proteomics reveals for the first time that ARID1A protein (BAF250a) binds aspartate transcarbamoylase (ATCase), a key regulatory enzyme of the de novo pyrimidine synthesis pathway. Using isogenic paired ARID1A proficient/deficient cancer cell lines, we show that ARID1A protein deficiency (as occurs in ARID1A mutant cancers) leads to metabolic reprogramming and pyrimidine synthesis dependency. Pyrimidine synthesis blockade using the FDA-approved drug teriflunomide (a DHODH inhibitor) suppresses tumor growth and selectively induces DNA damage in ARID1A-deficient tumor models. Combining pyrimidine synthesis inhibition with DNA damage repair blockade, using teriflunomide and AZD6738 (an ATR inhibitor), achieves potent synergy and induces sustained tumor regression in ARID1A-mutant ovarian cancer patient-derived xenografts (PDX). These compelling preclinical data support the evaluation of this novel combination treatment in patients with ARID1A-mutated cancers. SIGNIFICANCEWe identified that ARID1A-deficient cells are selectively vulnerable to pyrimidine synthesis blockade. Preclinical studies demonstrate the in vivo efficacy of a synergistic drug combination that concurrently inhibits the de novo pyrimidine synthesis pathway and DNA damage repair to induce regression in patient-derived xenograft models of ARID1A-mutated cancer.

cancer biology↗