Sex reversal in salmonid culture

Johnstone, R.; Simpson, T. H.; Youngson, A. F.; Whitehead, C. C.

doi:10.1016/0044-8486(79)90096-6

Cited by 95 publications

(48 citation statements)

References 6 publications

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“…Although this has yet to be demonstrated, it raises the possibility that E 2 could have important regulatory role(s) within the fish ovary. During fish early embryonic development, ERs are implicated in sex determination (Guigen et al 1999) and treatment of male fish with E 2 results in intersex (Krisfalusi & Nagler 2000) or phenotypic sex reversal (Johnstone et al 1978, Yamazaki 1983. The presence of ER mRNA in immature rainbow trout ovaries containing OFDs c100 µm in this study suggests that ERs may be important for normal sexual differentiation of the ovaries in genetic females.…”

Section: Discussionmentioning

confidence: 99%

Quantification of rainbow trout (Oncorhynchus mykiss) estrogen receptor-alpha messenger RNA and its expression in the ovary during the reproductive cycle

Nagler

Krisfalusi²,

Cyr³

2000

Journal of Molecular Endocrinology

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This study developed a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method to measure estrogen receptor-(ER ) mRNA in the rainbow trout (Oncorhynchus mykiss). Using RT-PCR, and primers based on the known ER DNA sequence in this species, cDNA sequences representing most of the protein coding region were obtained from ovary poly A(+) RNA. Using these DNA sequences as probes in Northern blot hybridizations confirmed that a single transcript of 4·2 kilobases in poly A(+) RNA could be detected in liver and ovary RNA. For the quantitative RT-PCR assay an internal standard RNA molecule was produced to control for inherent inter-tube differences in amplification efficiency and permit accurate quantification of ER mRNAs. The quantitative RT-PCR assay proved to be highly specific for ER mRNA with a detection limit of 6·9 fg, which corresponds to 273 fg ER mRNA/µg total RNA. The quantitative RT-PCR assay was used to measure the levels of ER mRNA in ovaries of rainbow trout at different stages of reproductive development. Ovarian ER mRNA expression was found during two distinct periods of reproductive development, in pre-vitellogenic ovaries of fish with ovarian follicle diameters (OFDs) c100 µm and in mid-vitellogenic ovaries with OFDs >1000 µm. ER mRNA could not be detected in the ovaries of fish with OFDs >100 µm but c1000 µm. The highest levels of ER mRNA were found in late vitellogenic ovaries of fish with OFDs >2000 µm.

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Section: Discussionmentioning

confidence: 99%

Quantification of rainbow trout (Oncorhynchus mykiss) estrogen receptor-alpha messenger RNA and its expression in the ovary during the reproductive cycle

Nagler

Krisfalusi²,

Cyr³

2000

Journal of Molecular Endocrinology

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“…These observations led to the postulate that androgens and estrogens are the substances responsible for sex differentiation of male and female fish, respectively (3), and has resulted in the development of protocols for the masculinization and feminization of large numbers of fish for experimental or economic purposes (1,4,5). The androgen receptor (AR) 1 is a critical mediator of male sexual differentiation and development in both fish and mammals.…”

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confidence: 99%

Two Distinct Isoforms of cDNA Encoding Rainbow Trout Androgen Receptors

Takeo

Yamashita

1999

Journal of Biological Chemistry

116

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Androgens play an important role in male sexual differentiation and development. The activity of androgens is mediated by an androgen receptor (AR), which binds to specific DNA recognition sites and regulates transcription. We describe here the isolation of two distinct rainbow trout cDNA clones, designated rtAR-␣ and rtAR-␤, which contain the entire androgen receptor coding region. Comparison of the predicted amino acid sequence of rtAR-␣ to that of rtAR-␤ revealed 85% identity. Interestingly, despite this high homology, rtAR-␣ activated transcription of an androgen-responsive reporter gene in co-transfection assays, but rtAR-␤ did not. These results suggest that rainbow trout contains two distinct isoforms of androgen receptors whose functions differ. The region of rtAR-␤ responsible for its inactivity was mapped to its ligand binding domain by analyzing chimeras of the rtAR-␣, rtAR-␤, and rtGR-I (glucocorticoid) receptors. Alteration of any one of three out of four segments within this domain restored activity.Extracts made from COS-1 cells transfected with an rtAR-␣ expression plasmid produced a high level of [ 3 H]mibolerone binding, whereas no binding was observed by extracts of cells transfected with an rtAR-␤ expression plasmid. These data demonstrate that the lack of transactivation activity of rtAR-␤ is due to its inability to bind hormone.In contrast to mammals, fish can undergo gonadal sex inversion in either direction by treatment with exogenous sex steroid if it is applied early enough during development (1, 2). These observations led to the postulate that androgens and estrogens are the substances responsible for sex differentiation of male and female fish, respectively (3), and has resulted in the development of protocols for the masculinization and feminization of large numbers of fish for experimental or economic purposes (1, 4, 5). The androgen receptor (AR) 1 is a critical mediator of male sexual differentiation and development in both fish and mammals. Structurally and functionally, the AR belongs to the superfamily of ligand-responsive transcription modifiers, which encompasses the receptors for the steroid and thyroid hormones. Like other nuclear receptors, steroid receptors are composed of three major functional domains: an NH 2 -terminal hypervariable transcriptional activation domain (TAD), a central highly conserved DNA binding domain (DBD) consisting of two Cys-Cys zinc finger motifs, and a COOH-terminal ligand binding domain (LBD) (6 -9). It has been reported that the AR regulates androgen target genes by binding to a specific DNA sequence, the androgen-responsive element (ARE; consensus ϭ 5Ј-GGTACANNNTGTTCT), which is similar to the glucocorticoid response element (12)(13)(14). The AR can either up-or downregulate the expression of androgen target genes, the outcome probably depending on interactions with specific adapters or co-activators (10, 11).At present, complete AR cDNAs have been cloned only from mammalian species (human, rat, and mouse) (6, 15). We have undertaken the isola...

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“…When methyltestosterone treatment is started at the onset of gonadal sex differentiation, the androgen has a masculinizing effect on the gonads (Johnstone et al, 1978 ;Okada etal., 1979 ;van den Hurk and Slof, 1981). A feminizing effect is observed when the fry are treated with oestradiol-17 (3 (!&dquo;) (Johnstone et al, 1978) A. Testes and D50 gonads. -The carriers added were : Adione, T, 11-ketoAdione, 11 /3-Adione, 11-keto-T and 11/3-T.…”

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confidence: 99%