Abstract 51: LincAQPEP, an Adipocyte-Specific Intergenic Noncoding RNA, Modulates Lipid Metabolism in Human Adipocytes

Long intergenic noncoding RNAs (lincRNAs) have emerged as key mediators of cellular functions and are increasingly implicated in human diseases. Recently a set of lincRNAs was identified to regulate adipogenesis in mice and humans. Here we report that lincAQPEP, a lincRNA predominantly expressed in adipose tissue, is one of the most abundant lincRNAs detected in human fat by RNA sequencing. It is highly expressed in mature adipocytes but not detected in pre-adipocytes, monocytes or macrophages, indicating its adipocyte specificity. Interestingly, no syntenic or conserved RNA transcript was detected in mouse genome for lincAQPEP, suggesting it might be a human specific lincRNA. A binding motif for PPAR gamma (PPARγ), a critical transcription factor in adipogenesis, was found in the promoter region of lincAQPEP (-612 to -596 bp relative to transcription start site). In addition, chromatin immunoprecipitation sequencing confirmed high occupancy of PPARγ around lincAQPEP transcription start site in human adipose tissue and cultured adipocytes, suggesting PPARγ may mediate adipocyte-specific lincAQPEP transcription. LincAQPEP knockdown (~70%) by lentiviral-based short hairpin RNAs resulted in ~35% decrease in triglyceride content as well as 30-70% reduction of lipogenic gene expression (e.g. SREBP1, FASN, FABP4) in human adipocytes, suggesting a modulatory role of lincAQPEP in adipocyte function. To investigate the molecular mechanisms of its regulatory function, we performed RNA pulldown assays with biotinylated lincAQPEP and lincAQPEP antisense transcript (negative control), followed by mass spectrometry to discover potential lincAQPEP-interacting proteins. IGF2BP3 (Insulin-like growth factor 2 mRNA-binding protein 3), implicated in post-transcriptional regulation of gene expression, was identified as one of top candidates to physically bind lincAQPEP. Interestingly, lincAQPEP knockdown resulted in ~30% reduction in IGF2BP3 mRNA abundance. These data suggested that lincAQPEP may impact mRNA stability and translation of specific genes by interacting with IGF2BP3. In summary, our data indicate that lincAQPEP, an adipose-specific lincRNA, plays important roles in adipocyte biology likely through interaction with IGF2BP3.