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Janes, Dan E

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Janes

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Dan E

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Janes, Dan E
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    Sex-Biased Expression of Sex-Differentiating Genes FOXL2 and FGF9 in American Alligators, Alligator mississippiensis
    (S. Karger AG, 2013) Janes, Dan E; Elsey, Ruth M.; Langan, E.M.; Valenzuela, Nicole; Edwards, Scott
    Across amniotes, sex-determining mechanisms exhibit great variation yet the genes that govern sexual differentiation are largely conserved. Studies of evolution of sex-determining and sex- differentiating genes require an exhaustive characterization of functions of those genes such as FOXL2 and FGF9. FOXL2 is associated with ovarian development and FGF9 is known to play a role in testicular organogenesis in mammals and other amniotes. As a step toward characterization of the evolutionary history of sexual development, we measured expression of FOXL2 and FGF9 across three developmental stages and eight juvenile tissue types in male and female American alligators, Alligator mississippiensis. We report surprisingly high expression of FOXL2 before the stage of embryonic development when sex is determined in response to temperature and sustained and variable expression of FGF9 in juvenile male but not female tissue types. Novel characterization of gene expression in reptiles with temperature-dependent sex determination such as American alligators may inform the evolution of sex-determining and sex-differentiating gene networks as they suggest alternative functions from which the genes may have been exapted. Future functional profiling of sex-differentiating genes should similarly follow other genes and other species to enable a broad comparison across sex-determining mechanisms.
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    Sex Chromosome Evolution in Amniotes: Applications for Bacterial Artificial Chromosome Libraries
    (Hindawi Publishing Corporation, 2010) Janes, Dan E; Valenzuela, Nicole; Ezaz, Tariq; Amemiya, Chris; Edwards, Scott
    Variability among sex chromosome pairs in amniotes denotes a dynamic history. Since amniotes diverged from a common ancestor, their sex chromosome pairs and, more broadly, sex-determining mechanisms have changed reversibly and frequently. These changes have been studied and characterized through the use of many tools and experimental approaches but perhaps most effectively through applications for bacterial artificial chromosome (BAC) libraries. Individual BAC clones carry 100–200 kb of sequence from one individual of a target species that can be isolated by screening, mapped onto karyotypes, and sequenced. With these techniques, researchers have identified differences and similarities in sex chromosome content and organization across amniotes and have addressed hypotheses regarding the frequency and direction of past changes. Here, we review studies of sex chromosome evolution in amniotes and the ways in which the field of research has been affected by the advent of BAC libraries.