Department of Biology, University of North Dakota, Grand Forks, ND 58202, USA. turk.rhen @ und.nodak.edu
Sex Dev. 2010;4(1-2):16-28. doi: 10.1159/000282495. Epub 2010 Feb 9.
Charles Darwin first provided a lucid explanation of how gender differences evolve nearly 140 years ago. Yet, a disconnect remains between his theory of sexual selection and the mechanisms that underlie the development of males and females. In particular, comparisons between representatives of different phyla (i.e., flies and mice) reveal distinct genetic mechanisms for sexual differentiation. Such differences are hard to comprehend unless we study organisms that bridge the phylogenetic gap. Analysis of variation within monophyletic groups (i.e., amniotes) is just as important if we hope to elucidate the evolution of mechanisms underlying sexual differentiation. Here we review the molecular, cellular, morphological, and physiological changes associated with sex determination in reptiles. Most research on the molecular biology of sex determination in reptiles describes expression patterns for orthologs of mammalian sex-determining genes. Many of these genes have evolutionarily conserved expression profiles (i.e., DMRT1 and SOX9 are expressed at a higher level in developing testes vs. developing ovaries in all species), which suggests functional conservation. However, expression profiling alone does not test gene function and will not identify novel sex-determining genes or gene interactions. For that reason, we provide a prospectus on various techniques that promise to reveal new sex-determining genes and regulatory interactions among these genes. We offer specific examples of novel candidate genes and a new signaling pathway in support of these techniques.
查尔斯·达尔文 (Charles Darwin) 近 140 年前首次清晰地解释了性别差异是如何进化的。然而，他的性选择理论与男性和女性发育的基础机制之间仍然存在脱节。特别是，不同门代表之间的比较（即苍蝇和老鼠）揭示了性分化的独特遗传机制。除非我们研究能够弥合系统发育差距的生物，否则很难理解这些差异。如果我们希望阐明性分化机制的进化，那么对单系群（即羊膜动物）内变异的分析同样重要。在这里，我们回顾了与爬行动物性别决定相关的分子、细胞、形态和生理变化。关于爬行动物性别决定的分子生物学的大多数研究都描述了哺乳动物性别决定基因的同源物的表达模式。这些基因中的许多具有进化上保守的表达谱（即，在所有物种中，DMRT1 和 SOX9 在发育中的睾丸中表达水平高于发育中的卵巢），这表明功能保守。然而，仅表达谱分析并不能检验基因功能，也不会鉴定新的性别决定基因或基因相互作用。因此，我们提供了各种技术的前景，这些技术有望揭示新的性别决定基因和这些基因之间的调控相互作用。我们提供了新的候选基因和新的信号通路的具体示例来支持这些技术。
