Characterizing the Epigenetic and Transcriptional Regulation of the Conjoined CHKB-CPT1B Locus

Abstract

The emergence of brown adipose tissue was an important event for vertebrate development; however, much is still unknown about this emergence. Previously, our lab showed that, in placental mammals, the Chkb and Cpt1b genes are conjoined and regulated by a singular upstream promoter region, whereas an intergenic CpG island prevents the conjunction of these genes in marsupials. Chkb encodes for choline kinase B (CHKB), which catalyzes the first step in phosphatidylcholine synthesis, while Cpt1b encodes for carnitine palmitoyltransferase 1B (CPT1B), which is the rate-limiting enzyme in fatty acid oxidation. We believe the loss of the marsupial intergenic CGI led to the conjunction of the Chkb-Cpt1b gene locus, and that CHKB is necessary for the brown adipocyte phenotype. In addition, we also believe lactylation, a novel form of epigenetic modification, is present across the Chkb-Cpt1b locus. In this dissertation, we show the intergenic CGI possesses enhancer and weak promoter activity and that CHKA, and not CHKB, is responsible for the majority of phosphatidylcholine synthesis in C2C12 and DE2.3 cells. We also show the presence of lactylation in these cells. We hope this data can be used to further our understanding of the emergence of brown adipocytes and provide future therapies to various diseases such as obesity.