Abstract
Male and female animals display innate sex-specific mating behaviors. In teleost fish, altering the adult sex steroid milieu can effectively reverse sex-typical mating behaviors, suggesting remarkable sexual lability of their brains as adults. In the teleost medaka, neuropeptide B (NPB) is expressed female-specifically in the brain nuclei implicated in mating behavior. Here, we demonstrate that NPB is a direct mediator of estrogen action on female mating behavior, acting in a female-specific but reversible manner. Analysis of regulatory mechanisms revealed that the female-specific expression of NPB is dependent on direct transcriptional activation by estrogen via an estrogen-responsive element and is reversed in response to changes in the adult sex steroid milieu. Behavioral studies of NPB knockouts revealed that female-specific NBP mediates female receptivity to male courtship. The female-specific NPB signaling identified herein is presumably a critical element of the neural circuitry underlying sexual dimorphism and lability of mating behaviors in teleosts.
Highlights
From invertebrates to humans, males and females of a given species exhibit profound differences in mating behavior; in general, males perform elaborate courtship displays to attract females for mating, and females evaluate male courtship displays to decide whether to mate
In the mutant female brain, npba expression was significantly reduced by ovariectomy and restored by E2 treatment, but E2 was not able to restore npba expression to the level present in wild-type females (p=0.0023 for the mutant versus wild-type females) (Figure 1G). These results demonstrate that estrogen elicits the female-specific expression of npba by direct transcriptional activation through the estrogen-responsive element (ERE) present in the npba promoter, other mechanisms are likely involved in this estrogen effect
We showed that npba expression in Vs/Vp and PMm/PMg of females was abolished by ovariectomy but restored by estrogen replacement (Hiraki et al, 2014)
Summary
Males and females of a given species exhibit profound differences in mating behavior; in general, males perform elaborate courtship displays to attract females for mating, and females evaluate male courtship displays to decide whether to mate. In the teleost species medaka (Oryzias latipes), we previously found that estrogen and androgen receptors are expressed almost exclusively in females in two brain regions: the supracommissural/ posterior nucleus of the ventral telencephalic area (Vs/Vp) and the magnocellular/gigantocellular portion of the magnocellular preoptic nucleus (PMm/PMg) (Hiraki et al, 2012) (Figure 1A,B). These regions are likely to represent female-specific target sites for both estrogen and androgen in the teleost brain. Our results demonstrate that NPB acts directly downstream of estrogen in a female-specific but reversible manner to mediate female sexual receptivity
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