The mechanism of sex determination in vertebrates-are sex steroids the key-factor?

Masahisa Nakamura*


    研究成果: Article査読

    128 被引用数 (Scopus)


    In many vertebrate species, sex is determined at fertilization of zygotes by sex chromosome composition, knows as genotypic sex determination (GSD). But in some species-fish, amphibians and reptiles-sex is determined by environmental factors; in particular by temperature-dependent sex determination (TSD). However, little is known about the mechanisms involved in TSD and GSD. How does TSD differ from GSD? As is well known, genes that activated downstream of sex-determining genes are conserved throughout all classes of vertebrates. What is the main factor that determines sex, then? Sex steroids can reverse sex of several species of vertebrate; estrogens induce the male-to-female sex-reversal, whereas androgens do the female-to-male sex-reversal. For such sex-reversal, a functioning sex-determining gene is not required. However, in R. rugosa CYP19 (P450 aromatase) is expressed at high levels in indifferent gonads before phenotypic sex determination, and the gene is also active in the bipotential gonad of females before sex determination. Thus, we may predict that an unknown factor, a common transcription factor locates on the X and/or W chromosome, intervenes directly or indirectly in the transcriptional up-regulation of the CYP19 gene for feminization in species of vertebrates with both TSD and GSD. Similarly, an unknown factor on the Z and/or Y chromosome probably intervenes directly or indirectly in the regulation of androgen biosynthesis for masculinization. In both cases, a sex-determining gene is not always necessary for sex determination. Taken together, sex steroids may be the key-factor for sex determination in some species of vertebrates.

    ジャーナルJournal of Experimental Zoology Part A: Ecological Genetics and Physiology
    313 A
    出版ステータスPublished - 2010 8月 1

    ASJC Scopus subject areas

    • 動物科学および動物学
    • 生態、進化、行動および分類学
    • 遺伝学
    • 生理学
    • 分子生物学


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