Pala I, Klüver N, Thorsteinsdóttir S, Schartl M, Coelho M M
Departamento de Biologia Animal, Faculdade de Ciências de Lisboa, Lisbon, Portugal.
Gene. 2008 Mar 15;410(2):249-58. doi: 10.1016/j.gene.2007.12.018. Epub 2008 Jan 2.
In fish of the Squalius alburnoides complex, hybridisation and polyploidy have affected sex ratios, resulting in strong correlations between sex and genotype. The preponderance of females among triploids and the occurrence of an all male lineage among diploids seem to imply that sex ratio deviations should have a strong genetic basis. Until now, no information has been gathered regarding the molecular basis of sex determination in this intricate hybrid system. Thus, putative regulatory elements of the cascade that potentially are involved in sex determination in S. alburnoides have to be investigated. Being reported to have an important role in teleost sex determination, and more particularly in male gonad development, the anti-Müllerian hormone, amh was a good initial candidate. Here we report the isolation, cloning and characterization of the amh ortholog in S. alburnoides and the ancestral species S. pyrenaicus. In adult S. alburnoides and S. pyrenaicus of both sexes, amh shows a gonad specific expression pattern, restricted to the Sertoli cell lineage in testis and to granulosa cells in ovaries. During development, it plays an early role in male gonad differentiation in S. alburnoides. Overall the observed patterns are similar to what has been reported in other teleost species. This suggests a conserved role of amh and implies that its expression dynamics cannot be directly responsible for the sex ratio deviations reported in S. alburnoides. It is possible that a conjunction of other factors could be contributing for sex ratio imbalance. The present results constitute the starting point in the characterization of the S. alburnoides sex determination cascade, a process that we expect to shed some light on the molecular basis of sex distribution, within the context of hybrid system evolution.
在阿尔巴尼亚鲤复合种的鱼类中，杂交和多倍体影响了性别比例，导致性别与基因型之间存在强烈的相关性。三倍体中雌性占优势以及二倍体中出现全雄谱系似乎意味着性别比例偏差应有很强的遗传基础。到目前为止，尚未收集到关于这个复杂杂交系统中性别决定分子基础的信息。因此，必须研究阿尔巴尼亚鲤中可能参与性别决定的级联反应的假定调控元件。抗缪勒氏管激素（amh）在硬骨鱼性别决定中，特别是在雄性性腺发育中具有重要作用，是一个很好的初始候选基因。在此，我们报告了阿尔巴尼亚鲤及其原始物种比利牛斯鲤中amh直系同源基因的分离、克隆和特征分析。在成年的阿尔巴尼亚鲤和比利牛斯鲤的两性中，amh呈现性腺特异性表达模式，在睾丸中局限于支持细胞谱系，在卵巢中局限于颗粒细胞。在发育过程中，它在阿尔巴尼亚鲤雄性性腺分化中起早期作用。总体而言，观察到的模式与其他硬骨鱼物种中报道的相似。这表明amh具有保守作用，并意味着其表达动态不能直接导致阿尔巴尼亚鲤中报道的性别比例偏差。可能是其他因素的共同作用导致了性别比例失衡。目前的结果构成了阿尔巴尼亚鲤性别决定级联反应特征分析的起点，我们期望这个过程能够在杂交系统进化的背景下，为性别分布的分子基础提供一些线索。
