Yao Capel 2005 - JB Urogenital Organ Development and...

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JB Minireview Reproductive / Urogenital Organ Development and Molecular Genetic Cascades J. Biochem. 138 , 5–12 (2005) DOI: 10.1093/jb/mvi097 Vol. 138, No. 1, 2005 5 © 2005 The Japanese Biochemical Society. Temperature, Genes, and Sex: a Comparative View of Sex Determination in Trachemys scripta and Mus musculus Humphrey H-C Yao 1 and Blanche Capel 2,* * To whom correspondence should be addressed at: 4026 GSRBII, Department of Cell Biology, Duke University Medical Center, Dur- ham, NC 27710, USA. Tel: +1-919-684-6390, Fax: +1-919-668-3467, E-mail: [email protected] 1 Department of Veterinary Biosciences, University of Illinois at Urbana-Champaign; and 2 Department of Cell Biology, Duke University Medical Center Received April 27, 2005; accepted May 11, 2005 Sex determination, the step at which differentiation of males and females is initiated in the embryo, is of central importance to the propagation of species. There is a remarkable diversity of mechanisms by which sex determination is accomplished. In general these mechanisms fall into two categories: Genetic Sex Determination (GSD), which depends on genetic differences between the sexes, and Environmental Sex Determination (ESD), which depends on extrinsic cues. In this review we will con- sider these two means of determining sex with particular emphasis on two species: a species that depends on GSD, Mus musculus, and a species that depends on ESD, Tra- chemys scripta . Because the structural organization of the adult testis and ovary is very similar across vertebrates, most biologists had expected that the pathways downstream of the sex-determining switch would be conserved. However, emerging data indicate that not only are the initial sex determining mechanisms different, but the downstream pathways and morphogenetic events leading to the development of a testis or ovary also are different. Key words: gonad, mouse, sex determination, turtle. Abbreviations: AMH , anti-Müllerian hormone; DMRT1 , Drosophila Doublesex and C. elegans Mab-3 related tran- scription factor 1; GSD, genetic sex determination; TSD, temperature-sensitive sex determination; Sry , sex-deter- mining region of the Y chromosome; SOX8 , Sry -like HMG-box protein 8; SOX9 , Sry -like HMG-box protein 9; SF1 , steroidogenic factor 1; WT1 , Wilm’s tumor gene 1; Wnt4 , wingless-related MMTV integration site 4; Bmp2 , bone morphogenic protein 2; FoxL2 , forkhead box L2. 1. Mechanisms of sex determination In GSD, sex is determined by genetic differences between individuals in the population. These may involve heteromorphic sex chromosomes or chromsomal regions, dosage differences of chromosomes or genes, or the cumulative effect of multiple variable alleles in the genome. The most familiar example of heteromorphic sex chromosomes is the case in humans, where males carry one X and one Y chromosome, and females carry two X chromosomes. This is the system employed by all mam- mals with the exception of a few species ( 1 ). In mammals
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Yao Capel 2005 - JB Urogenital Organ Development and...

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