Department of Cellular and Molecular Medicine and Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America.
PLoS One. 2018 Sep 12;13(9):e0202747. doi: 10.1371/journal.pone.0202747. eCollection 2018.
Snail2 is a zinc-finger transcription factor best known to repress expression of genes encoding cell adherence proteins to facilitate induction of the epithelial-to-mesenchymal transition. While this role has been best documented in the developmental migration of the neural crest and mesoderm, here we expand on previously reported preliminary findings that morpholino knock-down of snai2 impairs the generation of hematopoietic stem cells (HSCs) during zebrafish development. We demonstrate that snai2 morphants fail to initiate HSC specification and show defects in the somitic niche of migrating HSC precursors. These defects include a reduction in sclerotome markers as well as in the Notch ligands dlc and dld, which are known to be essential components of HSC specification. Accordingly, enforced expression of the Notch1-intracellular domain was capable of rescuing HSC specification in snai2 morphants. To parallel our approach, we obtained two mutant alleles of snai2. In contrast to the morphants, homozygous mutant embryos displayed no defects in HSC specification or in sclerotome development, and mutant fish survive into adulthood. However, when these homozygous mutants were injected with snai2 morpholino, HSCs were improperly specified. In summary, our morpholino data support a role for Snai2 in HSC development, whereas our mutant data suggest that Snai2 is dispensable for this process. Together, these findings further support the need for careful consideration of both morpholino and mutant phenotypes in studies of gene function.
Snail2 是一种锌指转录因子，以抑制编码细胞黏附蛋白的基因表达而闻名，从而促进上皮-间质转化的发生。虽然其在神经嵴和中胚层的发育迁移中的作用已得到充分证实，但在这里我们扩展了先前报道的初步发现，即 snai2 的 morpholino 敲低会损害斑马鱼发育过程中造血干细胞 (HSC) 的生成。我们证明 snai2 morphants 无法启动 HSC 特化，并显示出迁移 HSC 前体细胞的体节龛中的缺陷。这些缺陷包括减少硬骨形成细胞标记物以及 Notch 配体 dlc 和 dld，它们是 HSC 特化的已知必需组成部分。因此，强制表达 Notch1 细胞内结构域能够挽救 snai2 morphants 中的 HSC 特化。为了与我们的方法平行，我们获得了 snai2 的两个突变等位基因。与 morphants 相反，纯合突变胚胎在 HSC 特化或硬骨形成细胞发育中没有缺陷，并且突变鱼存活到成年期。然而，当这些纯合突变体被注射 snai2 morpholino 时，HSCs 被不正确地特化。总之，我们的 morpholino 数据支持 Snai2 在 HSC 发育中的作用，而我们的突变数据表明 Snai2 对于该过程不是必需的。总之，这些发现进一步支持在研究基因功能时，需要仔细考虑 morpholino 和突变表型。
