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Mozaffari, S. V.

Publications and source records attributed to Mozaffari, S. V..

3 recordsLinked to original sources

Parent of origin gene expression in a founder population identifies two new imprinted genes at known imprinted regions

Genomic imprinting is the phenomena that leads to silencing of one copy of a gene inherited from a specific parent. Mutations in imprinted regions have been involved in diseases showing parent of origin effects. Identifying genes with evidence of parent of origin expression patterns in family studies allows the detection of more subtle imprinting. Here, we use allele specific expression in lymphoblastoid cell lines from 306 Hutterites related in a single pedigree to provide formal evidence for parent of origin effects. We take advantage of phased genotype data to assign parent of origin to RNA-seq reads in individuals with gene expression data. Our approach identified known imprinted genes, two putative novel imprinted genes, and 14 genes with asymmetrical parent of origin gene expression. We used gene expression in peripheral blood leukocytes (PBL) to validate our findings, and then confirmed imprinting control regions (ICRs) using DNA methylation levels in the PBLs.\n\nAuthor SummaryLarge scale gene expression studies have identified known and novel imprinted genes through allele specific expression without knowing the parental origins of each allele. Here, we take advantage of phased genotype data to assign parent of origin to RNA-seq reads in 306 individuals with gene expression data. We identified known imprinted genes as well as two novel imprinted genes in lymphoblastoid cell line gene expression. We used gene expression in PBLs to validate our findings, and DNA methylation levels in PBLs to confirm previously characterized imprinting control regions that could regulate these imprinted genes.

genetics

Parent of Origin Effects on Quantitative Phenotypes in a Founder Population

The impact of the parental origin of associated alleles in GWAS has been largely ignored. Yet sequence variants could affect traits differently depending on whether they are inherited from the mother or the father. To explore this possibility, we studied 21 quantitative phenotypes in a large Hutterite pedigree. We first identified variants with significant single parent (maternal-only or paternal-only) effects, and then used a novel statistical model to identify variants with opposite parental effects. Overall, we identified parent of origin effects (POEs) on 11 phenotypes, most of which are risk factors for cardiovascular disease. Many of the loci with POEs have features of imprinted regions and many of the variants with POE are associated with the expression of nearby genes. Overall, our results indicate that POEs, which are often opposite in direction, are relatively common in humans, have potentially important clinical effects, and will be missed in traditional GWAS.

genetics

Rare non-coding variants are associated with plasma lipid traits in a founder population

Founder populations are ideally suited for studies on the clinical effects of alleles that are rare in general populations but occur at higher frequencies in these isolated populations. Whole genome sequencing in 98 South Dakota Hutterites, a founder population of European descent, and subsequent imputation to the Hutterite pedigree revealed 660,238 single nucleotide polymorphisms (SNPs; 98.9% non-coding) that are rare (<1%) or absent in European populations, but occur at frequencies greater than 1% in the Hutterites. We examined the effects of these rare in European variants on plasma levels of LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), total cholesterol and triglycerides (TG) in 828 Hutterites and applied a Bayesian hierarchical framework to prioritize potentially causal variants based on functional annotations. We identified two novel non-coding rare variants associated with LDL-C (rs17242388 in LDLR) and HDL-C (rs189679427 between GOT2 and APOOP5), and replicated previous associations of a splice variant in APOC3 (rs138326449) with TG and HDL-C. All three variants are at well-replicated loci in genome wide association study (GWAS) but are independent from and have larger effect sizes than the known common variation in these regions. We also identified variants at two novel loci (rs191020975 in EPHA6 and chr1:224811120 in CNIH3) at suggestive levels of significance with LDL-C. Candidate expression quantitative loci (eQTL) analyses in lymphoblastoid cell lines (LCLs) in the Hutterites suggest that these rare non-coding variants are likely to mediate their effects on lipid traits by regulating gene expression. Overall, we provide insights into the mechanisms regulating lipid traits and potentially new therapeutic targets.

genetics