Fibronectin Type III Domain Containing Protein 3B (FNDC3B)

The deduced mouse protein contains 1,207 amino acids. Both the mouse and human proteins contain 9 repeats of the fibronectin type III domain and a single transmembrane domain. Northern blot analysis and quantitative PCR (Q-PCR) in mouse 3T3-L1 preadipocytes and 3T3-F442A cells showed that Fndc3b is expressed transiently at the early stages of adipocyte differentiation, reaching a peak at 3 hours after induction of adipogenesis. Fndc3b expression was detected in adipocyte differentiable 3T3-L1 cells but not in the nonadipogenic NIH-3T3 cell line. Q-PCR detected high levels of Fndc3b expression in mouse white adipose tissue, with predominant expression in preadipocytes, but low expression in other organs, including brown adipose tissue.