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

Abstract

The production of an adequate number of gametes is necessary for normal reproduction, for which the regulation of proliferation from early gonadal development to adulthood is key in both sexes. Cystic proliferation of germline stem cells is an especially important step prior to the beginning of meiosis; however, the molecular regulators of this proliferation remain elusive in vertebrates. Here, we report that ndrg1b is an important regulator of cystic proliferation in medaka. We generated mutants of ndrg1b that led to a disruption of germ cells cystic proliferation. 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 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.

Reproductive roles of the vasopressin/oxytocin neuropeptide family in teleost fishes

“…In addition to oxtr paralogues, the expression of other teleost nonapeptide receptors and in some instances specific paralogues have been localized to tissues relevant to teleost reproduction (63)(64)(65)(66)(67)(68)(69)(70)(71)(72)(73) and are summarized in Table 3. Much of our current information on reproductive roles of nonapeptides has been derived from studies of otocephalan species including the airbreathing catfish (4, 5, 24, 84), goldfish (85-87), and zebrafish (35).…”

Sperm collection and computer-assisted sperm analysis in the teleost model Japanese medaka (Oryzias latipes)

“…While fish sperm is usually activated in the surrounding water, ovarian fluid increases or extends the duration of sperm motility in many species (Zadmajid et al, 2019). Although medaka are externally fertilizing freshwater fish, their spawning behavior, which includes fin wrapping and quivering, puts them in much closer proximity than broadcast spawners (Arias Padilla et al, 2021). As the osmolality of ovarian fluid in freshwater fish (about 300 mOsmol/kg) is close to HBSS (Zadmajid et al, 2019), it is possible that fluid released by the female activates the sperm, not the aquarium water.…”

“…Reproduction is one of the fields in biology where teleosts and medaka have been extensively used as model organisms. Indeed, medaka males show interesting reproductive and social behaviors, such as mate guarding (Arias Padilla et al, 2021; Okuyama et al, 2017). In addition, several transgenic lines exist to study the neuroendocrine control of reproduction in this species (Hodne et al, 2019; Karigo et al, 2014; Okubo et al, 2006).…”

Paternal methotrexate exposure affects sperm small RNA content and causes craniofacial defects in the offspring

“…Dissected testis from adult males (Control and 10MTX groups) were used for gene expression analysis. For this purpose, a complete testis from 8 males were individually grinded in 300 µl of TRIzol Reagent (Life Technologies) and total RNAs (~800ng/testis) were isolated and retrotranscribed 85 . Expression of target genes were measured by qPCR using Fast Start Universal SYBR green Supermix (Roche Diagnostics, USA) on Thermal Cycler…”

“…StepOne Plus (Applied Biosystem,USA), using ribosomal protein L7 (rpl7) and elongation factor 1 alpha (ef1α) as reference genes with the geometric mean calculation as described by Padilla et al 85 . Real-time PCR primers are listed in Supplementary Table 6.…”