Molecular characterization and transcriptional analysis of fad24 in pigs

Fad24 is a novel gene involved in initiating adipogenesis. Most of the current information on fad24 is limited to mice, and the transcriptional regulation of fad24 remains unknown. Here we revealed that porcine fad24 encodes a protein structurally homologous to its human and rodent orthologs. Like its mouse counterpart, pig fad24 had positive effect on the adipogenic differentiation of mesenchymal stem cells (MSCs). Distinct fad24 expression patterns were observed during development of skeletal muscle and subcutaneous fat in pigs. The proximal promoter region of porcine fad24 was predicted to contain a number of transcription factor binding motifs related to both adipogenesis and myogenesis. Among them, a putative binding site for krüppel-like factor (KLF)-15 was chosen for further analysis because the role of KLF15 in early adipogenesis is unclear, although its expression in preadipocytes is up-regulated shortly after adipogenic induction. We demonstrated that expression of fad24 and klf15 is concomitantly up-regulated at the onset of adipogenesis in MSCs. Functional KLF15 significantly enhanced the promoter activity of fad24, whereas dominant negative KLF15 had no such effects. Transactivation of fad24 by KLF15 was further confirmed by site-directed mutation and chromatin immunoprecipitation assays. Taken together, our findings provide additional information on fad24 that may contribute to understanding the molecular events involved in early adipocyte differentiation.