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

Steroid hormones appear to play an important role in gonadal sex differentiation of birds. Here we studied the steady-state level of the P450 arom mRNA by reverse transcriptase polymerase chain reaction (RT-PCR) in the left and the right presumptive ovary and testis of developing chicken embryos. Th...

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Bibliographic Details
Published in:General and comparative endocrinology 2000-03, Vol.117 (3), p.325-334
Main Authors: Villalpando, I., Sánchez-Bringas, G., Sánchez-Vargas, I., Pedernera, E., Villafán-Monroy, H.
Format: Article
Language:English
Subjects:
Androstenedione - metabolism
Animals
aromatase
Aromatase - genetics
Aromatase - metabolism
chick embryo
Chick Embryo - growth & development
estrogen
Estrone - metabolism
Female
Gene Expression
gonadal differentiation
Male
ovary
Ovary - embryology
Ovary - enzymology
Reverse Transcriptase Polymerase Chain Reaction
Sex Differentiation - genetics
testis
Testis - embryology
Testis - enzymology
Tritium
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Summary:Steroid hormones appear to play an important role in gonadal sex differentiation of birds. Here we studied the steady-state level of the P450 arom mRNA by reverse transcriptase polymerase chain reaction (RT-PCR) in the left and the right presumptive ovary and testis of developing chicken embryos. The gonads were evaluated every hour during the undifferentiated period, at 144–156 h of incubation (h/i), and every 24 h after sexual differentiation at 168 and 192 h/i. Activity of P450 arom was determined by estrone production from [3H]androstenedione at 144–192 h/i. Moreover, morphological development of the gonad was also examined by light microscopy. Results show that onset of P450 arom mRNA and its protein activity were simultaneously detected in the left and the right ovaries at 147 h/i. Asymmetric function of P450 arom gene expression was observed at 156 h/i when morphological gonadal differentiation is first recognized. Biotransformation of [3H]androstenedione to estrone was also asymmetrically detected between the left and right gonad at 156 h/i and asymmetry was maintained throughout the analyzed stages. It is proposed that there is a gene in birds that is asymmetrically expressed in the undifferentiated stage of the female and the male gonad. In the female this gene could promote P450 arom gene expression, increasing estrogen production, which in turn could induce ovarian cortex proliferation and expression of other structural estrogen-regulated genes involved in ovarian sexual determination.
ISSN:0016-6480
1095-6840
DOI:10.1006/gcen.2000.7425