Forkhead box O1 in grass carp Ctenopharyngodon idella: Molecular characterization, gene structure, tissue distribution and mRNA expression in insulin-inhibited adipocyte lipolysis

FoxO1a and FoxO1b, were firstly isolated and characterized from grass carp Ctenopharyngodon idella, encoding peptides of 654 and 631 amino acids, respectively. Phylogenetic and synteny analyses suggested that FoxO1a and FoxO1b were derived from paralogous genes that could be originated from teleost-specific genome duplication (TSGD) event. Analysis of the exon-intron structures clarified that grass carp FoxO1a and FoxO1b comprise 3 coding exons and contain a extra intron compared with human and mouse FoxO1. Both FoxO1a and FoxO1b mRNAs were expressed in a wide range of tissues, but the abundance of each FoxO1 mRNA showed the tissue- dependent expression patterns. Time-course analysis of FoxO1 expressions indicated that the level of FoxO1a mRNA reached almost maximal level at day 2, while that of FoxO1b mRNA reached almost maximal level at day 4 during grass carp primary preadipocyte differentiation. In insulin-inhibited adipocyte lipolysis, only FoxO1a showed a significant decrease in adipocyte, indicating that two FoxO1 isoforms may serve somewhat different roles in the regulation of lipolysis by insulin. These results suggested that grass carp FoxO1a and FoxO1b may play different roles in tissues, and their expression levels were differently modulated by insulin in adipocyte.