A novel, functional, and highly divergent sex hormone-binding globulin that may participate in the local control of ovarian functions in salmonids.

A cDNA encoding for a novel rainbow trout SHBG was identified and characterized. Phylogenetic analysis showed that this novel SHBG, named SHBGb, was a highly divergent paralog of the classical SHBG (SHBGa) form previously known in vertebrates including zebrafish, seabass, and rainbow trout. Using all available sequences, no SHBGb-like sequence could be identified in any fish species besides Atlantic salmon. Rainbow trout SHBGa and SHBGb share only 26% sequence identity at the amino acid level and exhibit totally distinct tissue distribution, thus demonstrating a functional shift of SHBGb. Indeed, shbga mRNA was predominantly expressed in liver and spleen but could not be detected in the ovary, whereas shbgb had a predominant ovarian expression but could not be detected in liver. Despite its high divergence, rainbow trout SHBGb expressed in COS-7 cells could bind estradiol and testosterone with high affinity and specificity. Both rainbow trout shbgb mRNA and proteins were localized to the granulosa cells of vitellogenic ovarian follicles, whereas SHBGb immunoreactivity was also found in theca cells. Finally, shbgb ovarian mRNA expression exhibited a significant drop between late vitellogenesis and oocyte maturation at a time when ovarian aromatase (cyp19a) gene expression and estradiol circulating levels exhibited a dramatic decrease. Together, these observations show that SHBGb is a functional and highly divergent SHBG paralog probably arising from a salmonid-specific duplication of the shbg gene.

Rainbow trout gonadal masculinization induced by inhibition of estrogen synthesis is more physiological than masculinization induced by androgen supplementation.

The present study was designed to obtain new insights into fish gonadal sex differentiation by comparing the effects of two different masculinizing treatments on some candidate gene expression profiles. Masculinization was induced in rainbow trout, Oncorhynchus mykiss, genetic all-female populations using either an active fish androgen (11betaAnd, 11beta-hydroxyandrostenedione) or an aromatase inhibitor (ATD, 1,4,6-androstatriene-3,17-dione). The expression profiles of 100 candidate genes were obtained by real-time RT-PCR, and 46 profiles displayed a significant differential expression between control populations (males and females) and ATD/11betaAnd-treated populations. These expression profiles were grouped in four temporally correlated expression clusters. Among the common responses shared by the two masculinizing treatments, the inhibition of some early female differentiating genes (cyp19a1, foxl2a, fst, and fshb) appears to be crucial for effective masculinization, suggesting that these genes act together via a short regulation loop to maintain high sex-specific ovarian expression of cyp19a1. This simultaneous down-regulation of female-specific genes could be triggered by some testicular genes, such as dmrt1, nr0b1 (also known as dax1), and pdgfra, which are quickly up-regulated by the two masculinizing treatments. In contrast to 11betaAnd, ATD quickly restored the expression levels of steroidogenesis related genes (cyp11b2.1, cyp11b2.2, hsd3b1, cyp17a, star, and nr5a1) and some Sertoli cell markers (sox9a2 and amh) to the expression levels observed during control testicular differentiation. This demonstrates that these genes are probably not needed for active masculinization and that the inhibition of endogenous estrogen synthesis produces a much more complete and specific testicular pattern of gene expression than that observed following androgen-induced masculinization.

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

Early differentiation in rainbow trout gonads was investigated by expression profiling and in situ hybridization (ISH). Expression of cyp19a1 and fst in females and sox9a1 in males were sexually dimorphic between 32 to 35 days post-fertilization (dpf). After 35 dpf, the differentiation proceeded with sexually dimorphic profiles for sox9a2, dmrt1, cyp11b2.1, amh in males and foxl2a, foxl2b, hsd3b1, inha in females. cyp17a1, cyp11a1, star, nr5a1b increased only after 40 dpf in both sexes with a slightly higher expression in females. cyp19a1 expression was localized in a cluster of somatic cells in the ventral side of female gonads, and sox9a2 and amh in somatic cells surrounding the germ cells, at 28 dpf and thereafter, both in male and female gonads. cyp11b2.1, cyp17a1, and cyp11a1 expressions were only detected in scattered somatic cells in males after 46 dpf. This confirms the early implication of cyp19a1 in trout ovarian differentiation and suggests that early testicular differentiation does not need androgen production.

Histología del ovario de Macrodon ancylodon (Bloch y Schneider, 1801) Teleostei: Sciaenidae) ovogénesis: folículos post-ovulatorios; atresia / Histology of the ovary of Macrodon ancylodon (Bloch and Schneider, 1801) Teleostei: Sciaenidae) oogenesis, post-ovulatory follicles, atresia

Realizou-se neste trabalho um estudo histológico do ovário de Macrodon ancylodon, com especial atençäo à ovogênese, aos folículos pós-ovulatórios e à atresia. Na seqüência da maturaçäo ovocitária se evidenciou a existência de 6 tipos celulares: ovogônias, ovócitos basófilos, ovócitos com vitelogênese lipídica, ovócitos com vitelogênese protéica, ovócitos com vitelogênese total e ovócitos hidratados. Os folículos pós-ovulatórios se caracterizaram por estruturas em degeneraçäo. Säo descritos dois tipos de atresia: a hipertrófica e a näo hipertrófica, que aparentemente näo teriam ligaçöes com um possível rol endócrino. As membranas ovulares (teca e granulosa) apresentaram um só tipo celular, sendo negativas as reaçöes histoquímicas para lipídios e colesterol