Blázquez Mercedes, Navarro-Martín Laia, Piferrer Francesc
Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Barcelona, Spain.
J Exp Zool B Mol Dev Evol. 2009 Nov 15;312(7):686-700. doi: 10.1002/jez.b.21286.
The European sea bass is a teleost fish that lacks sex chromosomes and for which temperature influences sex ratios. However, correlation between temperature, developmental stage at a given age and sex-specific gene expression is hampered by the lack of sex markers. To study this correlation, fish were exposed to feminizing (15 degrees C) or masculinizing temperature (21 degrees C) from 0-120 days post fertilization, throughout the thermosensitive period (TSP). Aromatase (cyp19a1a), 11beta-hydroxylase (cyp11b), androgen receptor (arb) and estrogen receptors (era, erb1 and erb2) were assessed by qPCR prior and during sex differentiation. Canonical discriminant analysis (CDA), with length--as proxy for developmental stage--and cyp19a1a expression as predictors, was validated and used to reliably assign gonadal sex to fish sampled within and outside the TSP. Differences in cyp19a1a and cyp11b expression could be detected 1-month before the first signs of histological sex differentiation. Cyp19a1a and cyp11b were significantly higher in future females and males, respectively, and revealed as robust molecular markers to predict future ovarian and testicular differentiation. In contrast, no association between phenotypic sex and arb, era, erb1 and erb2 expression was found, suggesting that these genes do not contribute to the differentiation of a particular sex. The CDA-based approach implemented here could be used to sex undifferentiated animals in species where genetic sex cannot be known owing to the lack of simple sex determining systems, as it is the case of many fish and reptiles with or without temperature-dependent sex determination, and provide a useful tool to relate gene expression and phenotypic sex.
欧洲海鲈是一种硬骨鱼，没有性染色体，温度会影响其性别比例。然而，由于缺乏性别标记，温度、特定年龄的发育阶段与性别特异性基因表达之间的相关性受到了阻碍。为了研究这种相关性，在受精后0至120天的整个热敏期（TSP），将鱼暴露于雌性化温度（15摄氏度）或雄性化温度（21摄氏度）下。在性别分化之前和期间，通过qPCR评估芳香化酶（cyp19a1a）、11β-羟化酶（cyp11b）、雄激素受体（arb）和雌激素受体（era、erb1和erb2）。以体长（作为发育阶段的代理）和cyp19a1a表达作为预测指标的典型判别分析（CDA）得到验证，并用于可靠地确定TSP内外采样鱼的性腺性别。在组织学性别分化的第一个迹象出现前1个月就能检测到cyp19a1a和cyp11b表达的差异。cyp19a1a和cyp11b分别在未来的雌性和雄性中显著更高，并被证明是预测未来卵巢和睾丸分化的强大分子标记。相比之下，未发现表型性别与arb、era、erb1和erb2表达之间存在关联，这表明这些基因对特定性别的分化没有贡献。这里实施的基于CDA的方法可用于在由于缺乏简单的性别决定系统而无法确定遗传性别的物种中对未分化动物进行性别鉴定，许多鱼类和爬行动物无论是否具有温度依赖性性别决定都是如此，并且为关联基因表达和表型性别提供了一个有用的工具。
