Adipogenesis, a differentiation process that transitions preadipocytes to adipocytes, is key to understanding the biology of fat accumulation and obesity. During this process, there many crucial transcription factors, such as PPAR gamma and the C/EBP family. Here we show a transcription factor in preadipocytes - Sox5, that has a function in porcine adipogenesis. In our porcine subcutaneous-derived preadipocyte differentiation model, we found Sox5 expression displayed a significant upregulation after initial induction and decreased afterwards, which resembles the PPAR gamma expression pattern. siRNA knockdown of Sox5 in porcine preadipocytes significantly promoted cell growth and accelerated cell cycle progression. After inducing differentiation, knockdown of Sox5 notably down-regulated the expression of adipogenic marker genes: PPAR gamma, aP2, FAS and impaired lipid accumulation. Mechanistically, the deletion of Sox5 down-regulated the BMP R-Smads signal pathway, a crucial signal pathway for controlling preadipocyte fate commitment and adipogenesis. After using BMP4 recombinant protein to activate the BMP R-Smads signal, Sox5 function was partially rescued. In conclusion, our findings uncovered a function of Sox5 in porcine adipogenesis and reveal an interaction between Sox5 and BMP signaling. (C) 2020 Elsevier Inc. All rights reserved.