Molecular Cloning, Expression, and In Situ Hybridization Analysis of Forkhead Box Protein L2 during Development in Macrobrachium nipponense

Forkhead box protein L2 (Foxl2) has dramatic effects on early differentiation and development of the female gonad in mammals and fish through the repression of SOX9 expression. In this study, we aimed to isolate a full-length cDNA sequence encoding Foxl2 from the Macrobrachium nipponense (Mn-Foxl2) and investigated its gene function. The full-length cDNA sequence of Mn-Foxl2 was 2097bp with an open reading frame of 1740bp, encoding 579 amino acids. Phylogenetic analysis revealed considerable evolutionary divergence between Mn-Foxl2 and Foxl2 from fish. Mn-Foxl2 may be involved in gonadal sex differentiation, based on its dramatically high expression during the sex-differentiation sensitive period. Tissue distributions indicated that Mn-Foxl2 mRNA expression was higher in the testis than that in the ovary and higher in males than in females in the same tissues, implying that Foxl2 may promote both male and female sexual development in M. nipponense. In situ hybridization analysis and quantitative polymerase chain reaction analysis in the gonad during the reproductive cycle further confirmed the important roles of Foxl2 in early gonad development in M. nipponense. This study advances our understanding of the role of Foxl2 in M. nipponense and provides the basis for further studies of Foxl2 in crustaceans.