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Tags
HERO ID
6549355
Reference Type
Journal Article
Subtype
Review
Title
The mechanism of sex determination in vertebrates-are sex steroids the key-factor?
Author(s)
Nakamura, M
Year
2010
Is Peer Reviewed?
1
Journal
Journal of Experimental Zoology. Part A: Ecological Genetics and Physiology
ISSN:
1932-5223
EISSN:
1932-5231
Volume
313
Issue
7
Page Numbers
381-398
Language
English
PMID
20623803
DOI
10.1002/jez.616
Web of Science Id
WOS:000280709200001
Abstract
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.
Keywords
Animals; Aromatase/genetics/metabolism; *Disorders of Sex Development; Female; Gene Expression Regulation, Developmental; Genotype; Gonadal Steroid Hormones/*physiology; Gonads/embryology/enzymology/physiology; Male; *Sex Determination Processes; Temperature; Vertebrates/*genetics
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