Identification, molecular characterization and gene expression analysis of sox1a and sox1b genes in Japanese flounder, Paralichthys olivaceus

• We isolated and characterized the two orthologs of sox1 from Paralichthys olivaceus.
• We analyzed the Posox1a and Posox1b promoter regions for potential TF binding sites.
• The gene expression profiles of Posox1a and Posox1b were analyzed by qRT-PCR.
• Posox1a and Posox1b were abundantly expressed at neurula stage and in adult brain.
• Posox1a and Posox1b may have a conserved function between teleosts and mammals.

The transcription factor, Sox1 has been implicated in neural determination and differentiation as well as in the maintenance of neural progenitor cell status in mammals. However, the molecular cloning and expression of sox1 gene in marine fish have not been reported yet. In this study, we first cloned and characterized the full-length cDNAs and the partial 5′-flanking regions of Paralichthys olivaceus sox1a (Posox1a) and sox1b (Posox1b). Phylogenetic, gene structure, and chromosome synteny analyses revealed that Posox1a and Posox1b were co-orthologs and homologous to mammalian Sox1. The promoter regions of Posox1a and Posox1b were also analyzed and several potential transcription factor (TF) binding sites were identified which might modulate gene expression. Quantitative real-time RT-PCR (qRT-PCR) results showed that Posox1a and Posox1b were consistently expressed during embryogenesis, with the highest level at the neurula stage. Tissue distribution analyses revealed that Posox1a and Posox1b were abundant in the adult brain. Moreover, Posox1a had a faster evolution rate and much higher expression levels than Posox1b. These results provide a foundation for further surveying the function of PoSox1 genes during Japanese flounder development and neurogenesis.