Molecular Aspects of Gonadal Differentiation in a Teleost Fish, the Nile Tilapia

Kobayashi, Tohru; Nagahama, Yoshitaka

doi:10.1159/000223076

Cited by 52 publications

(26 citation statements)

References 144 publications

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“…Consequently, sex differentiation and meiosis initiate earlier in female than in male. Consistently, in the present study, the expression of cyp19a1a started earlier in the Ctrl-XX and MTCE 2 -XX (5 dah) female or the sex reversed E 2 -XY and MTCE 2 -XY (10 dah) female than the expression of cyp11b2 in the Ctrl-XY male or the sex reversed MT-XX (30 dah) male, and meiosis initiate earlier in the normal and sex reserved female (30 dah) than in the normal and sex reserved male (85 dah) (Kobayashi & Nagahama 2009). One possible explanation might be that oogenesis takes more time than spermatogenesis as the oocytes need to deposit bulk nutrients for the developing embryos which is time consuming.…”

Section: Discussionsupporting

confidence: 92%

Simultaneous exposure to estrogen and androgen resulted in feminization and endocrine disruption

Chen¹,

Jiang²,

Feng³

et al. 2016

Journal of Endocrinology

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Estrogen, which is synthesized earlier in females than androgen in males, is critical for sex determination in non-mammalian vertebrates. However, it remains unknown that what would happen to the gonadal phenotype if estrogen and androgen were administrated simultaneously. In this study, XY and XX tilapia fry were treated with the same dose of 17a-methyltestosterone (MT) and 17b-estradiol (E 2 ) alone and in combination from 0 to 30 days after hatching. Treatment of XY fish with E 2 resulted in male to female sex reversal, while treatment of XX fish with MT resulted in female to male sex reversal. In contrast, simultaneous treatment of XX and XY fish with MT and E 2 resulted in female, but with cyp11b2 and cyp19a1a co-expressed in the ovary. Serum 11-ketotestosteron level of the MT and E 2 simultaneously treated XX and XY female was similar to that of the XY control, while serum E 2 level of these two groups was similar to that of the XX control. Transcriptomic cluster analysis revealed that the MT and E 2 treated XX and XY gonads clustered into the same branch with the XX control. However a small fraction of genes, which showed disordered expression, may be associated with stress response. These results demonstrated that estrogen could maintain the female phenotype of XX fish and feminize XY fish even in the presence of androgen. Simultaneous treatment with estrogen and androgen up-regulated the endogenous estrogen and androgen synthesis, and resulted in disordered gene expression and endocrine disruption in tilapia.

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Section: Discussionsupporting

confidence: 92%

Simultaneous exposure to estrogen and androgen resulted in feminization and endocrine disruption

Chen¹,

Jiang²,

Feng³

et al. 2016

Journal of Endocrinology

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“…We consider this stage the actual critical period of sex differentiation in tilapia, being the period when the decision towards the development of ovaries or testes is being made, and it has been established from 9 to 15 dpf by our group [Baroiller et al, 2009] and that of Nagahama [Ijiri et al, 2008]. During this stage the gonads in both sexes are mainly composed of supporting cells with few primordial germ cells (PGC) with an increase in the number of PGC in XX females starting around 13-14 dpf (9-10 dph) [Kobayashi and Nagahama, 2009]. In comparison to the early sexual dimorphism found for brain amh expression, the gonads had similar amh expression in both XY males and XX females during the 10-15-dpf period.…”

Section: Discussionmentioning

confidence: 99%

“…the germ cell number being higher in female gonads. The third period, 20-26 dpf, corresponds to an active ovarian mitosis, just before ovarian meiosis ( ϳ 28 dpf) which is the stage when the ovary is considered morphologically differentiated Kobayashi and Nagahama, 2009].…”

Section: Amh Expression Profiles In Tilapia Heads During Sex Differenmentioning

confidence: 99%

Elevated amh Gene Expression in the Brain of Male Tilapia (Oreochromis niloticus) during Testis Differentiation

Poonlaphdecha¹,

Pepey²,

Huang³

et al. 2010

Sex Dev

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Anti-müllerian hormone (AMH) is expressed in male embryos and represses development of müllerian ducts during testis differentiation in mammals, birds and reptiles. Amh orthologues have been identified in teleosts despite them lacking müllerian ducts. Previously we found sexually dimorphic aromatase activity in tilapia brains before ovarian differentiation. This prompted us to search for further dimorphisms in tilapia brains during sex differentiation and see whether amh is expressed. We cloned the tilapia amh gene and found that it contains 7 exons but no spliced forms. The putative protein presents highest homologies with Amh proteins of pejerrey and medaka as compared to other Perciformes. We analysed amh expression in adult tissues and found elevated levels in testes, ovary and brain. Amh expression was dimorphic with higher levels in XY male brains at 10–15 dpf, when the gonads were still undifferentiated and gonadal amh was not dimorphic. Male brains had 2.7-fold higher amh expression than gonads. Thereafter, amh levels decreased in the brain while they were up-regulated in differentiating testes. Our study indicates that amh is transcribed in male brains already at 10 dpf, suggesting that sexual differentiation may be occurring earlier in tilapia brain than in gonads.

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“…The developmental processes of gonadogenesis have been intensively investigated in species such as the zebrafish Danio rerio and Japanese medaka Oryzias latipes as vertebrate models for basic and applied studies [Uchida et al, 2002;2004;Saito and Tana-ka, 2009]. Similar studies have also been performed in economically important species such as the rainbow trout Oncorhynchus mykiss , tilapia Oreochromis niloticus and sea bass Dicentrarchus labrax [Vizziano et al, 2007;Piferrer and Guiguen, 2008;Kobayashi and Nagahama, 2009]. Another species that has attracted attention from an environmental perspective is the pejerrey Odontesthes bonariensis because sex determination in this species is strongly labile to water temperature early in life [Strüss-mann et al, 1996a[Strüss-mann et al, , 1997.…”

Section: Introductionmentioning

confidence: 99%

Thermal and Endocrine Regulation of Gonadal Apoptosis during Sex Differentiation in Pejerrey Odontesthes bonariensis

Yamamoto

Kitahara²,

Kimura³

et al. 2013

Sex Dev

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The fate of the differentiating gonads in pejerrey Odontesthesbonariensis is determined by the environmental water temperature experienced by the larvae during the critical period of sex determination. We previously reported a link between apoptosis, temperature and sex differentiation in this species. To clarify this link, we subjected larvae to thermal and endocrine treatments between hatching and the onset of histological sex differentiation of the gonads and assessed the patterns of gonadal development and apoptosis by light microscopic histology and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) analysis, respectively. Apoptotic labeling was widespread among somatic cells of the anterior region of the right gonads of fish reared at the male-producing temperature (MPT) and part of the fish at the mixed sex-producing temperature prior to sex differentiation. In contrast, TUNEL-positive cells were rarely observed in gonads at the female-producing temperature (FPT). Administration of exogenous estrogen completely prevented MPT-induced masculinization, induced feminization and reduced gonadal apoptosis, whereas an aromatase inhibitor (fadrozole) induced TUNEL signals in the gonads of FPT-reared larvae. These results provide strong evidence that apoptosis in somatic cells in the right lobe of the gonads might play a key role in testicular differentiation in pejerrey and that estrogens are involved in the regulation of this process.

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Molecular Aspects of Gonadal Differentiation in a Teleost Fish, the Nile Tilapia

Cited by 52 publications

References 144 publications

Simultaneous exposure to estrogen and androgen resulted in feminization and endocrine disruption

Simultaneous exposure to estrogen and androgen resulted in feminization and endocrine disruption

Elevated <i>amh</i> Gene Expression in the Brain of Male Tilapia <i>(Oreochromis niloticus) </i>during Testis Differentiation

Thermal and Endocrine Regulation of Gonadal Apoptosis during Sex Differentiation in Pejerrey <b><i>Odontesthes</i></b> <b><i>bonariensis</i></b>

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