A Novel pro-adipogenesis factor abundant in adipose tissues and over-expressed in obesity acts upstream of PPARγ and C/EBPα.

An important question about adipogenesis is how master adipogenesis factors (defined as being able to initiate adipogenesis when expressed alone) peroxisome proliferator-activated receptor (PPAR) initiate adipogenesis only in differentiating preadipocytes. The objective of our research was to find previously unidentified factors that are unique or highly enriched in cells of the adipocyte lineage during adipogenesis that may provide functional tissue specificity to preadipocytes. We reasoned that such factors may alter expression profile specifically in obese individuals. Omental adipose tissues were obtained from obese and non-obese male patients undergoing emergency abdominal surgery. mRNAs extracted from either group were used for suppression subtraction hybridization (SSH). Genes corresponding to mRNAs enriched in obese versus non-obese patients were identified through sequencing and further analyzed for tissue distribution. Out of ~20 genes, we found several that showed clear fat cell specific expression patterns. In this study, we functionally studied one of these genes, previously designated as open reading frame C10orf116. Our data demonstrated that C10orf116 is highly expressed in adipose tissue and is localized primarily within the nucleus. Over-expression studies in 3T3-L1 cells indicated that it up-regulates the levels of CCAAT/enhancer binding protein α (C/EBPα) and PPARγ and promotes adipogenic differentiation starting from the early stage of adipogenesis. Over-expressed in omental tissues from obese patients, C10orf16 manifested the characteristics of an adipocyte lineage-specific nuclear factor that can modulate the master adipogenesis transcription factors early during differentiation. Further studies of this factor should help reveal tissue-specific events leading to fat cell development at the transcriptional level.