34 research outputs found

    Brief exposure of embryos to steroids or aromatase inhibitor induces sex reversal in Nile tilapia (Oreochromis niloticus)

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    peer reviewedThis study aimed to develop sex reversal procedures targeting the embryonic period as tools to study the early steps of sex differentiation in Nile tilapia with XX, XY and YY sexual genotypes. XX eggs were exposed to masculinizing treatments with androgens (17α-methyltestosterone, 11-ketotestosterone) or aromatase inhibitor (Fadrozole), whereas XY and YY eggs were subjected to feminizing treatments with estrogen analog (17α-ethynylestradiol). All treatments consisted of a single or double 4-h immersion applied between 1 and 36 h post-fertilization (hpf). Concentrations of active substances were 1000 or 2000 µg l-1 in XX and XY, and 2000 or 6500 µg l-1 in YY. Masculinizing treatments of XX embryos achieved a maximal sex reversal rate of 10 % with an exposure at 24 hpf to 1000 µg l-1 of 11-ketotestosterone or to 2000 µg l-1 of Fadrozole. Feminization of XY embryos was more efficient and induced up to 91 % sex reversal with an exposure to 2000 µg l-1 of 17α-ethynylestradiol. Interestingly, similar treatments failed to reverse YY fish to females, suggesting either that a sex determinant linked to the Y chromosome prevents the female pathway when present in two copies, or that a gene present on the X chromosome is needed for the development of a female phenotype

    Sex determination and differentiation in teleost:Roles of genetics, environment, and brain

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    The fish reproductive system is a complex biological system. Nonetheless, reproductive organ development is conserved, which starts with sex determination and then sex differentiation. The sex of a teleost is determined and differentiated from bipotential primordium by genetics, environmental factors, or both. These two processes are species-specific. There are several prominent genes and environmental factors involved during sex determination and differentiation. At the cellular level, most of the sex-determining genes suppress the female pathway. For environmental factors, there are temperature, density, hypoxia, pH, and social interaction. Once the sexual fate is determined, sex differentiation takes over the gonadal developmental process. Environmental factors involve activation and suppression of various male and female pathways depending on the sexual fate. Alongside these factors, the role of the brain during sex determination and differentiation remains elusive. Nonetheless, GnRH III knockout has promoted a male sex-biased population, which shows brain involvement during sex determination. During sex differentiation, LH and FSH might not affect the gonadal differentiation, but are required for regulating sex differentiation. This review discusses the role of prominent genes, environmental factors, and the brain in sex determination and differentiation across a few teleost species

    Molecular cloning, expression analysis and transcript localization of testicular orphan nuclear receptor 2 in the male catfish, Clarias batrachus

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    Testicular receptor 2 (TR2; also known as Nr2c1) is one of the first orphan nuclear receptors identified and known to regulate various physiological process with or without any ligand. In this study, we report the cloning of full length nr2c1 and its expression analysis during gonadal development, seasonal testicular cycle and after human chorionic gonadotropin (hCG) induction. In addition, in situ hybridization (ISH) was performed to localize nr2c1 transcripts in adult testis and whole catfish (I day post hatch). Tissue distribution and gonadal ontogeny studies revealed high expression of nr2c1 in developing and adult testis. Early embryonic stage-wise expression of nr2c1 seems to emphasize its importance in cellular differentiation and development Substantial expression of nr2c1 during pre-spawning phase and localization of nr2c1 transcripts in sperm/spermatids were observed. Significant upregulation after hCG induction indicate that nr2c1 is under the regulation of gonadotropins. Whole mount ISH analysis displayed nr2c1 expression in notochord indicating its role in normal vertebrate development. Taken together, our findings suggest that nr2c1 may have a plausible role in the testicular and embryonic development of catfish. (C) 2016 Published by Elsevier Inc

    Expression Patterns of CREBs in Oocyte Growth and Maturation of Fish.

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    In fish, oocyte meiotic maturation is regulated by 17α, 20β-dihydroxy-progesterone through cAMP. To study the role of cAMP response element binding protein (CREB) in meiotic maturation, we cloned and characterized the expression pattern of CREBs from two fish models, the Nile tilapia and catfish. In the Nile tilapia three different CREBs were identified where in CREB1 was found in many tissues including gonads with abundant expression in testis. CREB2, few amino acids shorter than CREB1, was expressed in several tissues with abundant expression in ovary. In addition, a 3'UTR variant form, CREB3 was exclusively found in ovary. During natural 14-day ovarian cycle of the Nile tilapia, CREB1 expression was stable throughout vitellogenesis with a sharp decrease on the day of spawning. In contrast, CREB2 remain unchanged throughout the ovarian cycle, however elevated in 11-day full-grown immature ovarian follicle and after hCG-induction. Interestingly, CREB3 expression was induced three folds on the day of spawning as well as during hCG-induced oocyte maturation. Based on the synergistic expression pattern, CREB1 is likely to control oocyte growth, whereas CREB 2 and 3 contribute to oocyte maturation in tilapia and the latter seems to be critical. In catfish, a single form of CREB showed a maximum expression during spawning phase and hCG-induced maturation both in vivo and in vitro augmented CREB expression. These results suggest that spatial and temporal expression of CREBs seems to be important for final oocyte maturation and may also regulate oocyte growth in fish

    Expression of tilapia CREBs during: (A) natural ovarian cycle and (B) hCG induced -oocyte maturation as determined by RT-PCR and Northern Blot respectively. A plasmid DNA with CREB partial cDNA was used as positive control (PC) and PCR reaction without RT was used as negative control (NC) (Ma, Marker). (C) Densitometric analysis of CREB2 and CREB3 (mean ±SEM of two independent experiments).

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    <p>Expression of tilapia CREBs during: (A) natural ovarian cycle and (B) hCG induced -oocyte maturation as determined by RT-PCR and Northern Blot respectively. A plasmid DNA with CREB partial cDNA was used as positive control (PC) and PCR reaction without RT was used as negative control (NC) (Ma, Marker). (C) Densitometric analysis of CREB2 and CREB3 (mean ±SEM of two independent experiments).</p

    Northern blot analysis of CREBs.

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    <p><b>(A)</b> Expression of CREBs in tilapia ovary and testis <b>(</b>VOF; Vitellogenic Ovarian Follicle; FIO, Full grown Immature Ovarian Follicle; MOF, Mature Ovarian follicle). <b>(B)</b> Representative densitometric analysis of CREB2 and CREB3 of tilapia. Bars depicting same letter are significantly different from each other (mean ±SEM of two independent experiments). <b>(C)</b> Northern blot analysis of CREBs catfish ovary <b>(</b>P, Preparatory; PS, Pre-spawning; S, Spawning). <i>Note</i>: only one form of CREB (~ 1.3 kb) in tilapia testis [CREB 1] while two forms of CREB (~2.85 [CREB 2] and ~2.75 kb [CREB 3]) in tilapia ovary.</p

    Tissue distribution pattern of tilapia CREBs as determined by semi-quantitative RT-PCR.

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    <p>A plasmid DNA of CREB partial cDNA was used as positive control (PC) and PCR reaction without RT was used as negative control (NC). (Ma, Marker; B, Brain; A, Adrenal; H, Heart; S, Spleen; L, Lung; I, Intestine; K, Kidney; M, Muscle; T, Testis; O, Ovary; F, Ovarian follicle).</p
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