Syne2b/Nesprin-2 Is Required for Actin Organization and Epithelial Integrity During Epiboly Movement in Zebrafish.

Syne2b/nesprin-2 is a giant protein implicated in tethering the nucleus to the cytoskeleton and plays an important role in maintaining cellular architecture. Epiboly is a conserved morphogenetic movement that involves extensive spreading and thinning of the epithelial blastoderm to shape the embryo and organize the three germ layers. Dynamic cytoskeletal organization is critical for this process, but how it is regulated remains elusive. Here we generated a zebrafish syne2b mutant line and analyzed the effects of impaired Syne2b function during early development. By CRISPR/Cas9-mediated genome editing, we obtained a large deletion in the syne2b locus, predicted to cause truncation of the nuclear localization KASH domain in the translated protein. Maternal and zygotic syne2b embryos showed delayed epiboly initiation and progression without defects in embryonic patterning. Remarkably, disruption of Syne2b function severely impaired cytoskeletal organization across the embryo, leading to aberrant clustering of F-actin at multiple cell contact regions and abnormal cell shape changes. These caused disintegration of the epithelial blastoderm before the end of gastrulation in most severely affected embryos. Moreover, the migration of yolk nuclear syncytium also became defective, likely due to disorganized cytoskeletal networks at the blastoderm margin and in the yolk cell. These findings demonstrate an essential function of Syne2b in maintaining cytoskeletal architecture and epithelial integrity during epiboly movement.

Syne2b/nesprin - 2是一种巨型蛋白质，与将细胞核连接到细胞骨架有关，在维持细胞结构方面发挥重要作用。外包是一种保守的形态发生运动，涉及上皮胚层的广泛扩展和变薄，以塑造胚胎并组织三个胚层。动态的细胞骨架组织对这一过程至关重要，但其调控机制仍不清楚。在此，我们构建了一个斑马鱼syne2b突变体系，并分析了早期发育过程中Syne2b功能受损的影响。通过CRISPR/Cas9介导的基因组编辑，我们在syne2b基因座上获得了一个大片段缺失，预计会导致翻译后的蛋白质中核定位KASH结构域的截断。母源和合子源的syne2b胚胎在外包起始和进展方面出现延迟，但胚胎模式形成无缺陷。值得注意的是，Syne2b功能的破坏严重损害了整个胚胎的细胞骨架组织，导致F - 肌动蛋白在多个细胞接触区域异常聚集以及细胞形状异常变化。在受影响最严重的胚胎中，这些变化导致在原肠胚形成结束前上皮胚层解体。此外，卵黄核合胞体的迁移也出现缺陷，可能是由于胚层边缘和卵黄细胞中细胞骨架网络紊乱所致。这些发现表明Syne2b在外包运动过程中在维持细胞骨架结构和上皮完整性方面具有重要功能。