Genome-wide association studies (GWAS) traditionally assume an additive model of genetic inheritance, where the genetic effect of a heterozygous genotype is exactly intermediate to the genetic effects of the two homozygous genotypes. However, we know that many alleles act in either a dominant or recessive fashion. Detecting the phenotypic effects of rare, recessive variants is especially challenging, due to the scarcity of rare, homozygous genotypes. Here, we propose to use data from 96,000 individuals from the Pakistan Genomic Resource (PGR) to quantify the effects of rare, recessive variants on a wide range of phenotypic traits and common, complex diseases. Our study leverages the high rates of inbreeding within the PGR (which increases the frequency of rare, homozygous genotypes), as well as extensive lifestyle, family history and genetic data from all participants.
The specific aims for our project are (1) Phase and impute variants into more than 96,000 PGR genomes using a reference panel that includes 6,200 high- coverage genome sequences from South Asia; (2) Test for associations between a wide range of phenotypes and genotype, using a combination of standard single-variant tests and novel homozygosity-mapping approaches; and (3) Infer historical models of consanguinity within the PGR, using the distributions of long runs of homozygosity (caused by consanguineous marriages) both within and between individuals.
The Pakistan Genomic Resource (PGR) is a unique cohort of individuals with extensive phenotypic data and high rates of consanguinity. We plan to leverage these attributes, along with the availability of genome-wide genotype data from PGR samples, to discover novel genetic variants that can help predict disease susceptibility and help improve our understanding of the genetic contributions to medically relevant biomarkers such as blood pressure and cholesterol levels.
