MON-LB017 Natural Genetic Variation in Humans Determines Basal and PPAR-Inducible Expression of PM20D1, a Putative Thermogenic Gene

Abstract

Thermogenesis by brown and beige adipocytes is a potential avenue to increased energy expenditure and thus management of obesity and metabolic syndrome. In mice, Pm20d1 has been previously identified as a candidate thermogenic gene, with its mRNA levels cold-induced and enriched in brown and beige versus white adipocytes, and with the potential mechanism of generating a novel uncoupling metabolite. Thiazolidinedione (TZD) antidiabetic drugs, which activate the PPARγ nuclear receptor, are potent stimuli for adipocyte browning, yet they fail to induce Pm20d1 expression mouse adipocytes or adipose tissue. In contrast, we show here that PM20D1 is one of the most strongly TZD-induced transcripts in human adipocytes, though not in samples from all individuals. Two putative PPARγ binding sites were identified near the gene’s transcription start site (TSS) in human but not mouse adipocytes. The ~4kb upstream binding site falls in a segmental duplication of a nearly identical intronic region ~2.5kb downstream of the TSS, and this duplication event occurred in the primate lineage and is absent in other mammals like mice. We demonstrate by chromatin immunoprecipitation and reporter assays that PPARγ binding and gene activation occur via this upstream duplicated site, thus explaining the species difference. Furthermore, this functional upstream PPARγ site has genetic variation in the human population, with one single nucleotide polymorphism (SNP) allele disrupting a PPAR response element. We show that this allele gives less activation by PPARγ and TZDs in reporter assays and reduced TZD activation of PM20D1 in patient-derived cultured adipocytes. In addition to this upstream variant that determines PPARγ regulation of PM20D1 in adipocytes, genotype at a distinct and unlinked variant >40kb downstream of the TSS strongly correlates with overall levels of PM20D1 expression in human fat as well as multiple other tissues. Seven tightly linked downstream SNP alleles correlate with very low PMD201 expression and correspondingly high DNA methylation at the TSS. These low PM20D1 expression variants may have phenotypic consequences, accounting for human genetic associations in this region with metabolic and neurodegenerative diseases. Overall, human PM20D1 expression is genetically variable at two levels, with genotype at downstream SNPs correlating with overall PM20D1 expression across tissues (an “on/off switch”), while the upstream PPARγ site SNP determines PPARγ and TZD regulation in adipose tissue (a “rheostat”). This human genetic variation in PM20D1 expression may ultimately inform precision medicine approaches. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. s presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.