The P450 Aromatase (P450 arom) Gene Is Asymmetrically Expressed in a Critical Period for Gonadal Sexual Differentiation in the Chick

Villalpando, Irma; Sánchez-Bringas, Guadalupe; Sánchez-Vargas, I.; Pedernera, E.; Villafan‐Monroy, Horacio

doi:10.1006/gcen.2000.7425

Cited by 31 publications

(16 citation statements)

References 35 publications

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“…Recently, aromatase mRNA expression and biotransformation of [ 3 H] androstenedione to estrone were found to be lower in the right gonad than in the left gonad in 6.5-and sevenday-old female embryos, but there was an increase of estrone synthesis in the right gonad at eight days (Villalpando et al, 2000). Therefore, our results confirm that during chick embryonic development, the atrophied right gonad functions as an ovary, at least for aromatase activity and estrogen synthesis.…”

Section: Discussionsupporting

confidence: 87%

Sex reversal and aromatase in chicken

et al. 2001

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Aromatase inhibitors administered before sexual differentiation of the gonads can induce sex reversal in female chickens. To analyze the process of sex reversal, we have followed for several months the changes induced by Fadrozole, a nonsteroidal aromatase inhibitor, in gonadal aromatase activity and in morphology and structure of the female genital system. Fadrozole was injected into eggs on day four of incubation, and its effects were examined during the embryonic development and for eight months after hatching. In control females, aromatase activity in the right and the left gonad was high in the middle third of embryonic development, and then decreased up to hatching. After hatching, aromatase activity increased in the left ovary, in particular during folliculogenesis, whereas in the right regressing gonad, it continued to decrease to reach testicular levels at one month. In treated females, masculinization of the genital system was characterized by the maintenance of the right gonad and its differentiation into a testis, and by the differentiation of the left gonad into an ovotestis or a testis; however, in all individuals, the left Müllerian duct and the posterior part of the right Müllerian duct were maintained. In testes and ovotestes, aromatase activity was lower than in gonads of control females (except in the right gonad as of one month after hatching) but remained higher than in testes of control and treated males. Moreover, in ovotestes, aromatase activity was higher in parts displaying follicles than in parts devoid of follicles. The main structural changes in the gonads during sex reversal were partial (in ovotestes) or complete (in testes) degeneration of the cortex in the left gonad, and formation of an albuginea and differentiation of testicular cords/tubes in the two gonads. Testicular cords/tubes transdifferentiated from ovarian medullary cords and lacunae whose epithelium thickened and became Sertolian. Transdifferentiation occurred all along embryonic and postnatal development; thus, new testicular cords/tubes were continuously formed while others degenerated. The sex reversed gonads were also characterized by an abundant fibrous interstitial tissue and abnormal medullary condensations of lymphoid-like cells; in the persisting testicular cords/tubes, spermatogenesis was delayed and impaired. Related to aromatase activity, persistence of too high levels of estrogens can explain the presence of oviducts, gonadal abnormalities and infertility in sex reversed females.

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Section: Discussionsupporting

confidence: 87%

Sex reversal and aromatase in chicken

et al. 2001

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“…At the onset of morphological asymmetry of the female gonads (day 7), both P450 arom and ERa were expressed at significantly higher levels in the left than in the right gonad. Similar asymmetry in P450 arom and ERa expression has also been described for developing chicken gonads (Yoshida et al 1996, Nakabayashi et al 1998, Villalpando et al 2000, Sakimura et al 2002. Estrogen-binding sites and ERa protein have been located to the germinal epithelium of the left gonad and to the medulla of both gonads in early chicken embryos of both sexes (Gasc 1980, Guioli & Lovell-Badge 2007, Ishimaru et al 2008.…”

Section: Era-mediated Effects In Quail Embryossupporting

confidence: 58%

“…Aromatase activity has been shown to be higher in female than in male gonads in the early quail and chicken embryo (Scheib et al 1985, Villalpando et al 2000, Vaillant et al 2001. Experiments where estrogen formation or action in the female bird embryo is inhibited confirm that estrogen is crucial for normal ovarian development and for regression of the right gonad (Scheib 1983, Elbrecht & Smith 1992, Abinawanto et al 1997, Burke & Henry 1999, Vaillant et al 2001.…”

Section: Era-mediated Effects In Quail Embryosmentioning

confidence: 98%

Selective estrogen receptor α activation disrupts sex organ differentiation and induces expression of vitellogenin II and very low-density apolipoprotein II in Japanese quail embryos

Mattsson

Olsson²,

Brunström

2008

Reproduction

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The Japanese quail (Coturnix japonica) is a widely used model species for studying the roles of steroid hormones in avian sex differentiation. The aim of the present study was to elucidate the significance of estrogen receptors a and b (ERa and ERb) in normal sex differentiation of the reproductive organs in the Japanese quail and in xenoestrogen-induced disruption of reproductive organ differentiation. Real-time PCR indicated that ERa (ESR1) mRNA is expressed in both right and left gonads and Müllerian ducts (MDs) in both sexes during early morphological differentiation. ERb (ESR2) transcripts were also detected in gonads and MDs, but at very low levels. Both receptor subtypes were expressed in the liver and may therefore mediate the expression of estrogen-regulated egg-yolk proteins. Aromatase mRNA was expressed at much higher levels in female than male gonads as early as embryonic day 5, indicating early sex differences in estrogen synthesis. Treatment with the ERa-selective agonist propyl pyrazole triol showed that frequently reported xenoestrogen effects, such as ovotestis formation, abnormal MD development, and hepatic expression of egg-yolk proteins, were induced by selective activation of ERa. Taken together, our results suggest that activation of ERa is crucial for estrogen-dependent sex differentiation of the reproductive organs and that ERa mediates xenoestrogen-induced toxicity during reproductive development in birds.

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“…In cane toads, a low expression level in undifferentiated animals continued into the 20-mm and 30-mm stages when sexual differentiation is already complete, as can be observed morphologically. Various degrees of p450arom expression before sexual differentiation have also been observed in the chicken and turtle, with in-depth analyses of differential expression between presumptive testes and ovaries (Villalpando et al, 2000;Ramsey et al, 2007). However, due to our inability to sex undifferentiated individuals, we cannot assess the undifferentiated gonadal expression in such detail.…”

Section: Discussionmentioning

confidence: 98%

Cloning and expression of candidate sexual development genes in the cane toad (Bufo marinus)

Abramyan

Feng

Koopman

2009

Developmental Dynamics

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The development of the reproductive system in bufonids (true toads) is unique in several respects: sexual differentiation occurs later than in other anurans, and toads develop a Bidder's organ, a rudimentary ovary that can be manipulated in males to produce mature oocytes. To illuminate the genesis of this unusual reproductive system, we isolated from the cane toad (Bufo marinus) the orthologues of several known vertebrate sex-determining genes, determined their primary structure, and studied their expression by reverse transcriptase-polymerase chain reaction and in situ hybridization of tissue sections. We report here that cane toad Sox9, Dmrt1, and p450aromatase (Cyp19a1) are highly homologous to their counterparts in other vertebrates. They show profiles of expression that generally follow patterns observed in other taxa, but with some novel features. Our data suggest that these genes likely play key roles in sex determination and early gonad development in bufonids.

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The P450 Aromatase (P450 arom) Gene Is Asymmetrically Expressed in a Critical Period for Gonadal Sexual Differentiation in the Chick

Cited by 31 publications

References 35 publications

Sex reversal and aromatase in chicken

Sex reversal and aromatase in chicken

Selective estrogen receptor α activation disrupts sex organ differentiation and induces expression of vitellogenin II and very low-density apolipoprotein II in Japanese quail embryos

Cloning and expression of candidate sexual development genes in the cane toad (Bufo marinus)

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