School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.
Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan.
Commun Biol. 2024 Apr 3;7(1):408. doi: 10.1038/s42003-024-06103-x.
The regressive evolution of independent lineages often results in convergent phenotypes. Several teleost groups display secondary loss of the stomach, and four gastric genes, atp4a, atp4b, pgc, and pga2 have been co-deleted in agastric (stomachless) fish. Analyses of genotypic convergence among agastric fishes showed that four genes, slc26a9, kcne2, cldn18a, and vsig1, were co-deleted or pseudogenized in most agastric fishes of the four major groups. kcne2 and vsig1 were also deleted or pseudogenized in the agastric monotreme echidna and platypus, respectively. In the stomachs of sticklebacks, these genes are expressed in gastric gland cells or surface epithelial cells. An ohnolog of cldn18 was retained in some agastric teleosts but exhibited an increased non-synonymous substitution when compared with gastric species. These results revealed novel convergent gene losses at multiple loci among the four major groups of agastric fish, as well as a single gene loss in the echidna and platypus.
独立进化支系的退行演化常常导致趋同表型。几个硬骨鱼类群体表现出胃的次生缺失，并且在无胃（无胃）鱼类中已经共同缺失了四个胃基因 atp4a、atp4b、pgc 和 pga2。对无胃鱼类的基因型趋同分析表明，在四个主要群体的大多数无胃鱼类中，四个基因 slc26a9、kcne2、cldn18a 和 vsig1 被共同缺失或失活。kcne2 和 vsig1 也分别在无胃单孔类动物针鼹和鸭嘴兽中缺失或失活。在棘鱼的胃中，这些基因在胃腺细胞或表面上皮细胞中表达。在一些无胃硬骨鱼类中保留了 cldn18 的同源物，但与胃物种相比，其非同义替换增加。这些结果揭示了四个主要无胃鱼类群体中多个基因座的新的趋同基因缺失，以及针鼹和鸭嘴兽中的单个基因缺失。
