The broad goal of the proposed research is to contribute to our knowledge base of how adipocyte differentiation works through both creative discovery and innovative experimental approaches. To do this, a possible regulatory role for the lipid metabolic enzyme Stearoyl-CoA Desaturase-1 (SCD-1) in the differentiation of adipocytes will be examined. Although a passive function for SCD-1 in adipocyte metabolism has been recognized for years, new evidence is accumulating that this enzyme helps to control fat cell development. Specifically, adipocytes from mice with a targeted deletion of SCD-1 are smaller and have increased levels of the transcription factor PPAR-gamma, the master regulator of adipogenesis. In addition, depletion of SCD-1 in 3T3-L1 adipocytes with shRNA technology both enhances adipogenesis and up-regulates PPAR-gamma expression/activity. However, the mechanism(s) for these remains unknown. The major aims of this research are 1) to confirm that lack of SCD-1 enhances adipogenesis in fibroblasts derived from SCD-1 -/- mice;2) to examine the putative gene and metabolic changes brought about by SCD-1 deficiency in adipocytes;and 3) to determine the molecular mechanism for the observed effect of loss of SCD-1 on adipogenesis, either by identifying a novel protein interaction partner for SCD-1 or an active metabolite produced (or removed) by this enzyme. The proposed research is divided into two parts, an observational arm and a mechanistic arm. In the observational arm, microarray and lipidomics analyses will be used to gain insight into the transcriptional and metabolite changes incurred by SCD-1 deficiency, respectively. In the mechanistic arm, complementation studies using "dead" mutant proteins will be employed to determine whether the enzymatic activity of SCD-1 is required for the effect of this gene on adipogenesis. Then, tandem affinity purification or high-pressure liquid chromatography and mass spectrometry will be used to either identify a protein partner for SCD-1 or a lipid metabolic product, respectively, that is responsible for the observed phenomenon in adipocytes. PUBLIC HEALTH RELEVANCE: Obesity and its medical consequences is one of the biggest health issues in our nation right now, and conventional wisdom dictates that preventing the growth of new adipocytes (fat cells) would be an effective way to combat this. However, evidence suggests that the failure of a person to generate new adipocytes may be a primary cause of the morbidities that often result from excess weight. Understanding the mechanisms that govern adipocyte development, including the roles of lipid metabolism genes such as Stearoyl-CoA Desaturase, is an important step towards reaching our goal of alleviating the negative health effects linked with obesity.