OVEX1, a novel chicken endogenous retrovirus with sex-specific and left-right asymmetrical expression in gonads.

Background: In chickens, as in most birds, female gonad morphogenesis is asymmetrical. Gonads appear first rather similarly, but only the left one undergoes full differentiation and gives rise to a functional ovary. The right gonad, in which the cortex does not develop, remains restricted to the medulla and finally regresses.

Subcellular and molecular mechanisms regulating anti-Müllerian hormone gene expression in mammalian and nonmammalian species.

Anti-Müllerian hormone (AMH) is best known for its role as an inhibitor of the development of female internal genitalia primordia during fetal life. In the testis, AMH is highly expressed by Sertoli cells of the testis from early fetal life to puberty, when it is downregulated by the action of testosterone, acting through the androgen receptor, and meiotic spermatocytes, probably acting through TNFalpha. Basal expression of AMH is induced by SOX9; GATA4, SF1, and WT1 enhance SOX9-activated expression.

Lhx9 expression during gonadal morphogenesis as related to the state of cell differentiation.

Lhx9 (LIM/Homeobox gene 9) encodes a transcription factor implicated in various developmental processes, including gonadogenesis. Our observations in the rat show that Lhx9 expression present in undifferentiated gonads disappears as epithelial cells differentiate into Sertoli cells and begin to express AMH. In rat and in chick testes, Lhx9 expression present in interstitial cells decreases progressively to become undetectable after birth.

Different patterns of anti-Müllerian hormone expression, as related to DMRT1, SF-1, WT1, GATA-4, Wnt-4, and Lhx9 expression, in the chick differentiating gonads.

In mammals, anti-Müllerian hormone (AMH) is produced by Sertoli cells from the onset of testicular differentiation and by granulosa cells after birth. In birds, AMH starts to be expressed in indifferent gonads of both sexes at a similar level and is later up-regulated in males. We previously demonstrated that, unlike in mammals, the onset of AMH expression occurs in chick embryo in the absence of SOX9.

Early expression of AMH in chicken embryonic gonads precedes testicular SOX9 expression.

In mammals, anti-Müllerian hormone (AMH) is produced by Sertoli cells from the onset of testicular differentiation and by granulosa cells only after birth. SOX9, a transcription factor related to the testis-determining factor SRY, is expressed in mouse testis 1 day before AMH. To determine the relationship between AMH and SOX9 in birds, we cloned the AMH promoter in search of SOX9 response elements, and we compared the expression of AMH and SOX9 in the gonads of chick embryos using in situ hybridization.