Two DM domain genes, DMY and DMRT1, involved in testicular differentiation and development in the medaka, Oryzias latipes

Abstract

The recent discovery of the DMY gene (DM domain gene on Y chromosome and one of the DMRT1 family genes) as a key determinant of male development in the medaka (Oryzias latipes) has led to its designation as the prime candidate gene for sex-determination in this species. This study focused on the sites and pattern of expression of DMY and DMRT1 genes during gonadal differentiation of medaka to further determine their roles in testis development. DMY mRNA and protein are expressed specifically in the somatic cells surrounding primordial germ cells (PGCs) in the early gonadal primordium, before morphological sex differences are seen. However, somatic cells surrounding PGCs never express DMY during the early migratory period. Expression of DMY persists in Sertoli cell lineage cells, from PGC-supporting cells to Sertoli cells, indicating that only DMY-positive cells enclose PGCs during mitotic arrest after hatching. DMRT1 is expressed in spermatogonium-supporting cells after testicular differentiation (20 -30 days after hatching), and its expression is much higher than that of DMY in mature testes. In XX sex-reversed testes, DMRT1 is expressed in the Sertoli cell lineage, similar to the expression of DMY in XY testes. These results suggest strongly that DMY regulates PGC proliferation and differentiation sex-specifically during early gonadal differentiation of XY individuals and that DMRT1 regulates spermatogonial differentiation. Developmental Dynamics 231:518 -526, 2004.

Sexual dimorphic expression of DMRT1 and Sox9a during gonadal differentiation and hormone‐induced sex reversal in the teleost fish Nile tilapia (Oreochromis niloticus)

“…A recent report on a study using chickens showed that ZW sex reversal from female to male was accompanied by DMRT1 expression in medullary cells, which developed into Sertoli cells (Smith et al, 2003). Furthermore, our recent study indicates that medaka DMRT1 is expressed in the germ-cell-surrounding cells and the intratesticular efferent duct, al- though medaka DMRT1 is expressed after testicular differentiation, unlike in tilapia (Kobayashi et al, 2004). In medaka, however, sex determining gene DMY, a DMRT1 orthologue, is expressed in germ-cell-surrounding cell lineage cells before sex differentiation (Kobayashi et al, 2004).…”

“…Furthermore, our recent study indicates that medaka DMRT1 is expressed in the germ-cell-surrounding cells and the intratesticular efferent duct, al- though medaka DMRT1 is expressed after testicular differentiation, unlike in tilapia (Kobayashi et al, 2004). In medaka, however, sex determining gene DMY, a DMRT1 orthologue, is expressed in germ-cell-surrounding cell lineage cells before sex differentiation (Kobayashi et al, 2004). Taken together, these results indicate that DMRT1 is expressed in Sertoli-celllineage cells specifically, suggesting that the findings from human, bird, and reptile models are consistent with the results for tilapia.…”

“…However, information on the distribution of DMRT1 within the gonads is limited to the mouse (Raymond et al, 1999) and the chicken (Smith et al, 2003). Although the distribution of DMRT1 in the gonads in medaka (Kobayashi et al, 2004) and zebrafish (Guo et al, 2005) was reported, these reports were not as thoroughly described. These studies have all shown that DMRT1 is dominantly expressed in the testis.…”

“…These findings strongly suggest that DMRT1 homologs are involved in testicular differentiation in the process of normal sex development and sex reversal in nonmammalian vertebrates. Unfortunately, in teleost fish, the expression profiles of DMRT1 compared with those of morphological sexual dimorphisms in terms of germ cell number and histogenesis have not been reported in any species except for medaka (Kobayashi et al, 2004). In medaka (Oryzias latipes), the sex-determining gene DMY has been identified, and this gene is a DMRT1 homolog (Matsuda et al, 2002(Matsuda et al, , 2003.…”

Characterization of early molecular sex differentiation in rainbow trout, Oncorhynchus mykiss

“…Using gene expression profiling and ISH, we were able to demonstrate that gonadal differentiation occurred much sooner, i.e., shortly after hatching and at least one month before the first signs of morphological gonadal differentiation. In fish, this early molecular differentiation period has been poorly investigated and is only well documented in the medaka, Oryzias latipes, with the early testicular expression of the DM domain gene, dmy (Kobayashi et al, 2004).…”