A novel germline and somatic cell expression of two sexual differentiation genes, Dmrt1 and Foxl2 in marbled goby (Oxyeleotris marmorata)

Marbled goby (Oxyeleotris marmorata) is a freshwater cultured fish in which males grow faster and larger than females, therefore, the efficient development of sex control biotechnologies will be helpful to increase the production and value in this species. However, the mechanisms governing sex determination in marbled goby are poorly understood, and little information about molecular factors of sexual differentiation is available. Dmrt1 and Foxl2 are two known factors that play critical roles in sexual differentiation in many animals. Here, we characterized a Dmrt1 homologue (omDmrt1) and two Foxl2 homologues (omFoxl2a and omFoxl2b) by analyzing their expression and localization during gonadal development in marbled goby. The expression of omDmrt1 was gonad-specific and testis-biased. omFoxl2a and omFox2b were mainly distributed in brain-pituitary-ovary axis, although their expression levels were quite different. The germline and somatic cell localization of omDmrt1, omFoxl2a and omFoxl2b in developing and mature gonads were revealed by fluorescent in situ hybridization. The expression of omDmrt1 was weak in spermatids, oogonia and early oocytes, moderate in testicular somatic cells, strong in spermatogenic cells including spermatocytes and spermatogonia where it was co-localized with the germ plasm-specific component omVasa. omFoxl2a was expressed not only in granulosa cells but also in female germlines including oogonia and oocytes at various stage. Notably, omFoxl2a was colocalized with omVasa in Balbiani bodies of early oocytes, suggesting that omFoxl2a might be involved in establishment of oocyte polarity, early oogenesis and ovarian differentiation. omFoxl2b was also weakly expressed in granulosa cells, oogonia and stage I oocyte. In summary, a novel germline and somatic cell expression pattern of omDmrt1, omFoxl2a and omFoxl2b was revealed in marbled goby, suggesting that they might play an important role in sexual differentiation and germ cell development in marbled goby.