Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, 76100, Rehovot, Israel.
Institute of Animal Science, Agricultural Research Organization, 50250, Bet Dagan, Israel.
Heredity (Edinb). 2020 Nov;125(5):317-327. doi: 10.1038/s41437-020-0340-x. Epub 2020 Jul 9.
Sex determination (SD) mechanisms are ancient and conserved, yet much diversity is exhibited in primary sex-determining signals that trigger male or female development. In O. niloticus, SD is associated with a male-specific locus on linkage group (LG) 23 which harbors the Y-linked Anti-Müllerian hormone (amh) gene, and a truncated duplication, denoted amhΔy. We have evaluated the possible role of identified indels and SNPs in the amh gene on SD, based on conservation in different O. niloticus strains. A fluorescent assay for the detection of a 5 bp insertion in amhΔy exon VI, efficiently discriminated between XX, XY, and YY genotypes. Concordance rate between amhΔy and sex varied in six Oreochromis strains, from 100% (Ghana) through 90% (Swansea) to 85% (Thai-Chitralada). The association of amhΔy with sex was found to be conserved in all tested O. niloticus strains, and thus supports its key role in SD. However, the previously identified missense SNP (C/T) in amh exon II was found only in the Swansea strain, thus excluding its candidacy for the causal variation of SD across all strains. Effects of markers on LGs 1, 3, and 23 (amhΔy) fully explained sex distribution in one Thai-Chitralada family (R = 1.0), whereas in another family only the major effect of LG23 (amhΔy) was significant (R = 0.37). Thus, amhΔy on LG23 is associated with genetic SD, either as a single causal gene in different O. niloticus strains, or in combination with segregating genes on LGs 1 and 3 in the Thai-Chitralada hybrid strain.
性别决定（SD）机制是古老而保守的，但触发雄性或雌性发育的主要性别决定信号表现出很大的多样性。在尼罗罗非鱼中，SD 与位于第 23 条连锁群（LG）上的一个雄性特异性位点相关，该位点包含 Y 连锁的抗缪勒管激素（amh）基因和一个截断的重复序列，称为 amhΔy。我们基于不同尼罗罗非鱼品系中的保守性，评估了 amh 基因中已鉴定的插入缺失和单核苷酸多态性（SNP）在 SD 中的可能作用。一种用于检测 amhΔy 外显子 VI 中 5bp 插入的荧光检测法，能够有效地区分 XX、XY 和 YY 基因型。amhΔy 和性别的一致性率在六个奥利亚罗非鱼品系中有所不同，从 100%（加纳）到 90%（斯旺西）到 85%（泰国-吉拉达）。amhΔy 与性别的关联在所有测试的尼罗罗非鱼品系中均被发现是保守的，因此支持其在 SD 中的关键作用。然而，在斯旺西品系中仅发现了 amh 外显子 II 中先前鉴定的错义 SNP（C/T），因此排除了其在所有品系中作为 SD 因果变异的候选基因。LGs 1、3 和 23（amhΔy）上的标记对一个泰国-吉拉达家系的性别分布的解释程度达到了 1.0（R），而在另一个家系中，只有 LG23（amhΔy）的主要效应是显著的（R=0.37）。因此，LG23 上的 amhΔy 与遗传性别决定有关，无论是在不同的尼罗罗非鱼品系中作为单一的因果基因，还是在泰国-吉拉达杂交品系中与 LGs 1 和 3 上分离的基因结合。
