Molecular Characterization, Expression Pattern and Transcriptional Regulation of Figla During Gonad Development in Japanese Founder (Paralichthys olivaceus)

The factor in the germline alpha (figla), as a member of the basic helix-loop-helix family, has been reported to be involved in ovary development in mammals and teleosts. However, the regulatory mechanisms of figla in teleosts remain unclear. Here, figla in P. olivaceus (Pofigla) was characterized with encoding a 202 amino acid protein that contains a conserved basic region and helix-loop-helix (HLH) domain. Amino acids alignment and synteny analysis revealed that Pofigla was conserved with the orthologous gene sequences in other vertebrates. The results of qRT-PCR showed Pofigla was maternally inherited during embryonic development. For tissue distribution, Pofigla showed a sexually dimorphic gene expression in the gonad of different genders, with a higher expression in ovary than in testis. In situ hybridization (ISH) results demonstrated Pofigla was specifically expressed in germ cells including oocytes, spermatogonia and spermatocytes. By screening and analyzing two proximal regions (-2966/-2126 and -772/-444) with high promoter activity, we found SOX5, LEF1, FOXP1 and GATA1 may play important roles in the transcriptional regulation of Pofigla. Furthermore, we observed the co-localization between Figla and LEF1 in HEK 293T cells. And the significant up-regulation effect of the canonical Wnt signaling pathway on the expression of Pofigla was found in cultured ovarian cells. This study provided the first evidence that figla not only has an important function in ovary development, but also plays some potential roles in testis development and/or male germ cell differentiation during early testis development in P. olivaceus. The results provide valuable reference in exploring the regulatory network of figla in teleost.