Nakagawa Hibiki, Kuroda Junpei, Aramaki Toshihiro, Kondo Shigeru
Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Dev Biol. 2022 Jan;481:52-63. doi: 10.1016/j.ydbio.2021.09.003. Epub 2021 Sep 17.
Spear-like collagen complexes, known as actinotrichia, underlie the epidermal cell layer in the tip of teleost fins and are known to contribute toward fin formation; however, their specific role remains largely unclear. In this study, we investigated of actinotrichia in the role of caudal fin formation by generating collagen9a1c (col9a1c)-knockout zebrafish. Although actinotrichia were initially produced normally and aligned correctly in the knockout fish, the number of actinotrichia decreased as the fish grew and their alignment became disordered. Simultaneously, the fin tip gradually shortened in the dorsal-ventral direction and the entire fin became oval-shaped, while the fin-rays rarely bifurcated and instead underwent fusion, suggesting that actinotrichia are essential for spreading fins dorsoventrally. Furthermore, the epithelial cells that are usually thinly spread in normal fish became spherical in the knockout fish, reducing the area covered by each cell and thus the area of the fin tip. Together, these findings suggest that the tight alignment of actinotrichia provides physical support in the dorsal-ventral direction that allows caudal fins to expand in a triangular-shape.
矛状胶原复合物，即棘状鳞，位于硬骨鱼鳍尖端的表皮细胞层之下，已知其对鳍的形成有作用；然而，它们的具体作用仍 largely 不清楚。在本研究中，我们通过生成胶原9a1c（col9a1c）基因敲除斑马鱼来研究棘状鳞在尾鳍形成中的作用。尽管在基因敲除鱼中棘状鳞最初正常产生且排列正确，但随着鱼的生长，棘状鳞的数量减少且排列变得紊乱。同时，鳍尖在背腹方向逐渐缩短，整个鳍变成椭圆形，而鳍条很少分叉而是发生融合，这表明棘状鳞对于鳍在背腹方向展开至关重要。此外，在正常鱼中通常 thinly 分布的上皮细胞在基因敲除鱼中变成球形，减少了每个细胞覆盖的面积，从而也减少了鳍尖的面积。总之，这些发现表明棘状鳞的紧密排列在背腹方向提供了物理支撑，使尾鳍能够呈三角形扩展。
