Involvement of oestrogens in sexual differentiation of gonads as a function of temperature in turtles

Dorizzi, Mireille; Mignot, Thérèse-Marie; Guichard, A.; Desvages, Giséle; Pieau, Claude

doi:10.1111/j.1432-0436.1991.tb00216.x

Cited by 80 publications

(43 citation statements)

References 30 publications

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“…they became phenotypic males) in response to testosterone injections (Shibata et al, 2002). These findings are particularly interesting since endogenous steroids (in particular estrogens) have been suggested as playing a pivotal role in sex determination in TSD reptiles Dorizzi et al, 1991;Lance and Bogart, 1991;Wibbels et al, 1991b;Wibbels and Crews 1992). It will be interesting to look at the effects of exogenous steroids on the expression of T. scripta Dmrt1 during the thermosensitive period.…”

Section: Discussionmentioning

confidence: 99%

Expression of Dmrt1 in a turtle with temperature-dependent sex determination

Murdock

Wibbels

2003

Cytogenet Genome Res

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There is a variety of sex determining mechanisms among vertebrates. Many reptiles possess temperature-dependent sex determination (TSD), in which the incubation temperature of the egg determines the sex of the hatchling. The red-eared slider turtle, Trachemys scripta has often been used as a model system for examining the physiology of TSD. In the current study, the expression of Dmrt1 was examined during TSD in this turtle. Dmrt1 is a putative regulator of sex determination/differentiation and has been identified in a variety of vertebrates, including fishes, amphibians, reptiles, birds, and mammals. Specifically, Dmrt1 has been shown to be up-regulated in a male-specific pattern during embryonic development in many vertebrates. In the current study, the expression patterns of Dmrt1 were examined in the developing adrenal-kidney-gonad complexes of T. scripta during embryonic development. Using a quantitative competitive RT-PCR, Dmrt1 was shown to be up-regulated during the thermosensitive period of sex determination in males. In contrast, levels of Dmrt1 remained low in females throughout the thermosensitive period. These data suggest that the up-regulation of Dmrt1 may play a role in male sex determination/sex differentiation during TSD in T. scripta.

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Section: Discussionmentioning

confidence: 99%

Expression of Dmrt1 in a turtle with temperature-dependent sex determination

Murdock

Wibbels

2003

Cytogenet Genome Res

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“…At stage 16, very low amounts of oestrogens were found at both male-producing temperature (25 C) and female-producing temperature (30 C). At stages 17 and 18, oestrogens remained detectable in very low amounts or were not detectable at the male-producing temperature, whereas higher levels of oestrogens were found at the female-producing temperature (Dorizzi et al 1991).…”

Section: Oestrogens Are Synthesized By the Gonads During The Tsp And mentioning

confidence: 95%

“…Assays were performed in embryos of E. orbicularis (Dorizzi et al 1991) and D. coriacea (Desvages et al 1993). In both species, the gonads were separated from the adrenal/mesonephros complexes and pooled.…”

Section: Oestrogens Are Synthesized By the Gonads During The Tsp And mentioning

confidence: 99%

Oestrogens and temperature-dependent sex determination in reptiles: all is in the gonads

Pieau¹,

Dorizzi²

2004

Journal of Endocrinology

156

117

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In many species of oviparous reptiles, the first steps of gonadal sex differentiation depend on the incubation temperature of the eggs. Feminization of gonads by exogenous oestrogens at a male-producing temperature and masculinization of gonads by antioestrogens and aromatase inhibitors at a female-producing temperature have irrefutably demonstrated the involvement of oestrogens in ovarian differentiation. Nevertheless, several studies performed on the entire gonad/adrenal/ mesonephros complex failed to find differences between male-and female-producing temperatures in oestrogen content, aromatase activity and aromatase gene expression during the thermosensitive period for sex determination. Thus, the key role of aromatase and oestrogens in the first steps of ovarian differentiation has been questioned, and extragonadal organs or tissues, such as adrenal, mesonephros, brain or yolk, were considered as possible targets of temperature and sources of the oestrogens acting on gonadal sex differentiation.In disagreement with this view, experiments and assays carried out on the gonads alone, i.e. separated from the adrenal/mesonephros, provide evidence that the gonads themselves respond to temperature shifts by modifying their sexual differentiation and are the site of aromatase activity and oestrogen synthesis during the thermosensitive period. Oestrogens act locally on both the cortical and the medullary part of the gonad to direct ovarian differentiation. We have concluded that there is no objective reason to search for the implication of other organs in the phenomenon of temperature-dependent sex determination in reptiles. From the comparison with data obtained in other vertebrates, we propose two main directions for future research: to examine how transcription of the aromatase gene is regulated and to identify molecular and cellular targets of oestrogens in gonads during sex differentiation, in species with strict genotypic sex determination and species with temperature-dependent sex determination.

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“…High levels of estradiol-17␤ and estrone in the gonad block the differentiation of testicular cords in medulla and enhance the proliferation of the germinal epithelium to differentiate into an ovary. Strong similarities exist between aromatase activity and estrogen content in the gonad during TSP, leading to the assumption that aromatase activity is a proxy of estrogen content in the gonad [Dorizzi et al, 1991]. The aromatase activity measured in the gonad was shown to be positively related to incubation temperature during TSP Pieau, 1991, 1992;Desvages et al, 1993].…”

Section: Estrogens and Aromatase Activity In The Gonadmentioning

confidence: 99%

Modeling Thermal Influence on Animal Growth and Sex Determination in Reptiles: Being Closer to the Target Gives New Views

Girondot

Hassine²,

Sellos

et al. 2010

Sex Dev

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Many species of oviparous reptiles, including crocodilians, a majority of turtles, some lizards and the 2 closely related species of Sphenodon have been shown to display temperature-dependent sex determination (TSD). Whereas it has been demonstrated very early that TSD also occurs in natural conditions, the relationship between a time series of changing temperatures and sex ratio remains a challenging problem for reptiles. We describe how a physiological model of embryo growth, gonadal development and aromatase activity can produce outputs that mimic well TSD. We provide an enhancement of a previously published model taking into account direct effect of temperature on aromatase activity. The comparison between the original model and the new one suggests that aromatase expression is controlled by a repressor factor expressed at masculinizing temperatures rather than its enhancement at feminizing temperatures.

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Involvement of oestrogens in sexual differentiation of gonads as a function of temperature in turtles

Cited by 80 publications

References 30 publications

Expression of Dmrt1 in a turtle with temperature-dependent sex determination

Expression of Dmrt1 in a turtle with temperature-dependent sex determination

Oestrogens and temperature-dependent sex determination in reptiles: all is in the gonads

Modeling Thermal Influence on Animal Growth and Sex Determination in Reptiles: Being Closer to the Target Gives New Views

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