Genetics and Breeding Center for Blunt Snout Bream, Ministry of Agriculture, Key Laboratory of Freshwater Aquatic Genetic Resources, Ministry of Agriculture, National Demonstration center for Experimental Fisheries Science Education (Shanghai Ocean University), Shanghai, 201306, China.
Sci Rep. 2019 Mar 11;9(1):4098. doi: 10.1038/s41598-019-40651-1.
The grass goldfish appeared early in the evolutionary history of goldfish, and shows heritable stability in the development of the caudal fin. The twin-tail phenotype is extremely rare, however, some twin-tail individuals were produced in the process of breeding for ornamental value. From mutations in the twin-tail goldfish genome, we identified two kinds of Tgf2 transposons. One type was completely sequenced Tgf2 and the other type was ΔTgf2, which had 858 bp missing. We speculate that the bifurcation of the axial skeletal system in goldfish may be caused by an endogenous ΔTgf2 insertion mutation in Chordin A, as ΔTgf2 has no transposition activity and blocks the expression of Chordin A. The twin-tail showed doubled caudal fin and accumulation of red blood cells in the tail. In addition, in situ hybridization revealed that ventral embryonic tissue markers (eve1, sizzled, and bmp4) were more widely and strongly expressed in the twin-tail than in the wild-type embryos during the gastrula stage, and bmp4 showed bifurcated expression patterns in the posterior region of the twin-tail embryos. These results provide new insights into the artificial breeding of genetically stable twin-tail grass goldfish families.
草金鱼出现在金鱼的早期进化历史中，其尾鳍的发育具有可遗传的稳定性。虽然双尾表型极为罕见，但在一些为了观赏价值而进行的繁殖过程中，会产生一些双尾个体。从双尾金鱼的基因组突变中，我们鉴定出两种 Tgf2 转座子。一种是完全测序的 Tgf2，另一种是缺失了 858bp 的ΔTgf2。我们推测，金鱼的轴骨骼系统的分叉可能是由于 Chordin A 中的内源性ΔTgf2 插入突变引起的，因为ΔTgf2 没有转座活性，并且会阻断 Chordin A 的表达。双尾金鱼的尾鳍呈现出两倍的大小，并且尾部的红细胞聚集。此外，原位杂交显示，在原肠胚期，双尾金鱼胚胎的腹侧胚胎组织标记物（eve1、sizzled 和 bmp4）的表达比野生型胚胎更为广泛和强烈，并且 bmp4 在双尾金鱼胚胎的后区域呈现出分叉的表达模式。这些结果为遗传稳定的双尾草金鱼家族的人工繁殖提供了新的见解。
