Eukaryotic initiation factor 4E binding protein family members are widely expressed in fish tissues: Cloning and distribution of 4E-BPs in Schizothorax prenanti

Schizothorax prenanti (Cypriniformes, Cyprinidae, Schizothoracinae) is an endemic, valuable fish in the southwest of China. Although a series of studies concerning the genetic and endocrine control of feeding and growth in S. prenanti have been examined in our laboratory, the mechanism is still unclear. To better understand these mechanisms, complete coding sequences of the eukaryotic initiation factor 4E binding proteins (4E-BP1, 4E-BP2 and 4E-BP3) were isolated in S. prenanti and their mRNA distributions examined in different tissues. S. prenanti 4E-BP1, 4E-BP2 and 4E-BP3 consisted of 120, 113 and 111 amino acids and exhibited a quite high degree of amino acid identity, respectively, to their cyprinid fish homologs. Phylogenetic analysis of the 4E-BPs sequences showed three main branches of vertebrate 4E-BPs. However, it was of interest that teleost 4E-BP1 clustered with vertebrate 4E-BP3, while the tetrapod 4E-BP1 formed a distinct clade. The mRNAs of all 4E-BPs were ubiquitously expressed in S. prenanti tissues, including brain, pituitary, eye, heart, gut, hepatopancreas, kidney, spleen, gonad, muscle, skin and gill. The widespread distributions suggest that 4E-BPs might have distinct physiological actions in S. prenanti, in particular on the brain, pituitary, gut, hepatopancreas and muscle, which involved feeding and growth regulation. This preliminary study opens the way for further functional studies on the mechanisms of the regulation of feeding and growth in S. prenanti and other teleost.