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Adipogenesis is accomplished via a complex series of steps, and the events at the earliest stage remain to be elucidated. To clarify the molecular mech-anisms of adipocyte differentiation, we previously isolated 102 genes expressed early in mouse 3T3-L1 preadipocyte cells using a PCR subtrac-tion system. | ễFEBS Journal A novel gene fad49 plays a crucial role in the immediate early stage of adipocyte differentiation via involvement in mitotic clonal expansion Tomoaki Hishida Tsuyoshi Eguchi Shigehiro Osada Makoto Nishizuka and Masayoshi Imagawa Department of Molecular Biology Graduate Schoolof PharmaceuticalSciences Nagoya City University Aichi Japan Keywords 3T3-L1 cell adipocyte differentiation CCAAT enhancer-binding protein obesity peroxisome proliferator-activated receptor c Correspondence M. Imagawa Department of Molecular Biology Graduate Schoolof Pharmaceutical Sciences Nagoya City University 3-1 Tanabe-dori Mizuho-ku Nagoya Aichi 4678603 Japan Fax 81 52 836 3455 Tel 81 52 836 3455 E-mail imagawa@phar.nagoya-cu.ac.jp Received 24 July 2008 revised 7 September 2008 accepted 11 September 2008 doi 10.1111 j.1742-4658.2008.06682.x Adipogenesis is accomplished via a complex series of steps and the events at the earliest stage remain to be elucidated. To clarify the molecular mechanisms of adipocyte differentiation we previously isolated 102 genes expressed early in mouse 3T3-L1 preadipocyte cells using a PCR subtraction system. About half of the genes isolated appeared to be unknown. After isolating full-length cDNAs of the unknown genes one of them named factor for adipocyte differentiation 49 fad49 appeared to be a novel gene as the sequence of this clone showed no identity to known genes. FAD49 contains a phox homology PX domain and four Src homology 3 SH3 domains suggesting that it may be a novel scaffold protein. We found that the PX domain of FAD49 not only has affinity for phosphoinositides but also binds to its third SH3 domain. Expression of fad49 was transiently elevated 3 h after differentiation was induced and diminished 24 h after induction. Induction of the fad49 gene was observed in adipocyte differentiable 3T3-L1 cells but not in non-adipogenic NIH-3T3 cells. RNAi-mediated knockdown of fad49 significantly impaired adipocyte differentiation. Moreover
