Laboratory of Aquatic Zoology, Marine Research Station, Institute of Cellular and Organismic Biology, Academia Sinica, Yilan, 26242, Taiwan.
Division of Developmental Biology, Department of Functional Morphology, Faculty of Medicine, School of Life Science, Tottori University, Nishi-cho 86, Yonago, 683-8503, Japan.
Sci Rep. 2024 Apr 15;14(1):8716. doi: 10.1038/s41598-024-58448-2.
Artificial selection has been widely applied to genetically fix rare phenotypic features in ornamental domesticated animals. For many of these animals, the mutated loci and alleles underlying rare phenotypes are known. However, few studies have explored whether these rare genetic mutations might have been fixed due to competition among related mutated alleles or if the fixation occurred due to contingent stochastic events. Here, we performed genetic crossing with twin-tail ornamental goldfish and CRISPR/Cas9-mutated goldfish to investigate why only a single mutated allele-chdS with a E127X stop codon (also called chdA)-gives rise to the twin-tail phenotype in the modern domesticated goldfish population. Two closely related chdS mutants were generated with CRISPR/Cas9 and compared with the E127X allele in F2 and F3 generations. Both of the CRISPR/Cas9-generated alleles were equivalent to the E127X allele in terms of penetrance/expressivity of the twin-tail phenotype and viability of carriers. These findings indicate that multiple truncating mutations could have produced viable twin-tail goldfish. Therefore, the absence of polymorphic alleles for the twin-tail phenotype in modern goldfish likely stems from stochastic elimination or a lack of competing alleles in the common ancestor. Our study is the first experimental comparison of a singular domestication-derived allele with CRISPR/Cas9-generated alleles to understand how genetic fixation of a unique genotype and phenotype may have occurred. Thus, our work may provide a conceptual framework for future investigations of rare evolutionary events in domesticated animals.
人工选择已广泛应用于遗传固定观赏驯养动物中的罕见表型特征。对于这些动物中的许多种，其罕见表型背后的突变基因座和等位基因已为人所知。然而，很少有研究探索这些罕见的遗传突变是否因相关突变等位基因之间的竞争而被固定，或者固定是否是由于偶然的随机事件所致。在这里，我们通过双尾观赏金鱼和 CRISPR/Cas9 突变金鱼进行遗传杂交，以探究为什么只有一个带有 E127X 终止密码子（也称为 chdA）的突变等位基因 chdS 导致现代家养金鱼群体出现双尾表型。我们用 CRISPR/Cas9 产生了两个密切相关的 chdS 突变体，并在 F2 和 F3 代中与 E127X 等位基因进行了比较。CRISPR/Cas9 产生的两个等位基因在双尾表型的外显率/表现度和携带者的活力方面与 E127X 等位基因相当。这些发现表明，多个截断突变可能产生了有活力的双尾金鱼。因此，现代金鱼中不存在多态性等位基因用于双尾表型，这可能源于随机消除或共同祖先中缺乏竞争等位基因。我们的研究首次对单一驯化衍生的等位基因与 CRISPR/Cas9 产生的等位基因进行了实验比较，以了解独特基因型和表型的遗传固定是如何发生的。因此，我们的工作可能为未来研究家养动物中罕见的进化事件提供一个概念框架。
