Rosa, I. F. | Search bioRxiv

bioRxiv2021

Gdnf, a germ cell-derived factor, regulates zebrafish germ cell stemness through the creation of new spermatogonial niches (germ and Sertoli cells) and inhibition of spermatogonial differentiation in an autocrine and paracrine manners

Glial cell line-derived neurotrophic factor (GDNF) and its receptor (GDNF Family Receptor 1 - GFR1) are well known to mediate spermatogonial stem cell (SSC) proliferation and survival in the mammalian testes. In nonmammalian species, Gdnf and Gfr1 orthologs have been found but their functions remain poorly investigated in the testis. Considering this background, this study aimed to understand the roles of Gdnf-Gfr1 signaling pathway in the zebrafish testis by combining in vivo, in silico and ex vivo approaches. Our analysis showed that zebrafish exhibited two paralogs of Gndf (gdnfa and gdnfb) and its receptor, Gfr1 (gfr1a and gfr1b), in agreement with the teleost-specific third round (3R) of whole genome duplication. Expression analysis further revealed that gdnfa and gfr1a were the most expressed copies in the zebrafish adult testes. Subsequently, we demonstrated that gdnfa is expressed in the germ cells, while Gfr1a was detected in early spermatogonia (mainly in types Aund and Adiff) and Sertoli cells. Functional ex vivo analysis showed that Gdnf promoted the creation of new available niches by stimulating proliferation of both type Aund spermatogonia and their surrounding Sertoli cells, but without changing pou5f3 mRNA levels. Strikingly, Gdnf also inhibited late spermatogonial differentiation as shown by the decrease of type B spermatogonia and down-regulation of dazl in the co-treatment with Fsh. Altogether, our data revealed for the first time that a germ cell-derived factor is associated with maintaining germ cell stemness through the creation of new available niches, supporting development of differentiating spermatogonial cysts and inhibiting late spermatogonial differentiation in autocrine and paracrine manners.

cell biology↗

bioRxiv2020

Cystic proliferation of embryonic germ stem cells is necessary to reproductive success and normal mating behavior in medaka

The production of an adequate number of gametes in both sexes is necessary for normal reproduction, for which the regulation of proliferation from early gonadal development to adulthood is key. Cystic proliferation of embryonic stem germ cells prior the onset of gametogenesis is an especially important step prior to the beginning of meiosis. However, in vertebrates, the molecular regulators of cystic proliferation remain unknown. Here, we report that ndrg1b, a member of the N-myc downstream regulated family, is an important regulator of cystic proliferation in medaka. We generated mutants of ndrg1b that led to a disruption of proliferation type II, independently of the TGF-{beta} signaling pathway. This loss of cystic proliferation was observed from embryogenic to adult stages, impacting the success of gamete production and reproductive parameters such as spawning and fertilization. Interestingly, the depletion of cystic proliferation of the ndrg1b mutant also impacted male sexual behavior, with a decrease of mating vigor. These data illustrate why it is also necessary to consider gamete production capacity in order to analyze reproductive behavior. HIGHLIGHTSO_LINdrg1b is involved in the regulation of cystic proliferation in gonad from embryo to adulthood. C_LIO_LIThe cystic proliferation is independently of the TGF-{beta} signaling pathway. C_LIO_LIDecrease of production of gametes declines reproductive success for both sexes. C_LIO_LIReduction of cystic proliferation declines male sexual behavior, with a decrease of mating vigor. C_LI

developmental biology↗