Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium.
PLoS One. 2014 Jan 7;9(1):e85608. doi: 10.1371/journal.pone.0085608. eCollection 2014.
The mouse genome consists of six functional actin genes of which the expression patterns are temporally and spatially regulated during development and in the adult organism. Deletion of beta-actin in mouse is lethal during embryonic development, although there is compensatory expression of other actin isoforms. This suggests different isoform specific functions and, more in particular, an important function for beta-actin during early mammalian development. We here report a role for beta-actin during neural crest ontogeny. Although beta-actin null neural crest cells show expression of neural crest markers, less cells delaminate and their migration arrests shortly after. These phenotypes were associated with elevated apoptosis levels in neural crest cells, whereas proliferation levels were unchanged. Specifically the pre-migratory neural crest cells displayed higher levels of apoptosis, suggesting increased apoptosis in the neural tube accounts for the decreased amount of migrating neural crest cells seen in the beta-actin null embryos. These cells additionally displayed a lack of membrane bound N-cadherin and dramatic decrease in cadherin-11 expression which was more pronounced in the pre-migratory neural crest population, potentially indicating linkage between the cadherin-11 expression and apoptosis. By inhibiting ROCK ex vivo, the knockout neural crest cells regained migratory capacity and cadherin-11 expression was upregulated. We conclude that the presence of beta-actin is vital for survival, specifically of pre-migratory neural crest cells, their proper emigration from the neural tube and their subsequent migration. Furthermore, the absence of beta-actin affects cadherin-11 and N-cadherin function, which could partly be alleviated by ROCK inhibition, situating the Rho-ROCK signaling in a feedback loop with cadherin-11.
鼠类基因组包含 6 个功能性肌动蛋白基因，这些基因在发育过程中和成年生物体中具有时空调节的表达模式。尽管其他肌动蛋白同工型存在补偿性表达，但β-肌动蛋白在胚胎发育过程中的缺失在小鼠中是致命的。这表明不同同工型具有特定的功能，特别是β-肌动蛋白在早期哺乳动物发育过程中具有重要功能。我们在这里报告了β-肌动蛋白在神经嵴发生中的作用。尽管β-肌动蛋白缺失的神经嵴细胞显示出神经嵴标记物的表达，但较少的细胞分离并且它们的迁移在短时间后停止。这些表型与神经嵴细胞中凋亡水平升高有关，而增殖水平不变。特别是，前迁移神经嵴细胞显示出更高水平的凋亡，这表明神经管中凋亡的增加导致β-肌动蛋白缺失胚胎中迁移的神经嵴细胞数量减少。这些细胞另外显示出缺乏膜结合型 N-钙粘蛋白，并且钙粘蛋白-11 的表达急剧下降，在前迁移神经嵴细胞群体中更为明显，这可能表明钙粘蛋白-11 表达与凋亡之间存在联系。通过体外抑制 ROCK，敲除神经嵴细胞恢复了迁移能力，并且钙粘蛋白-11 的表达上调。我们得出结论，β-肌动蛋白的存在对于存活至关重要，特别是对于前迁移的神经嵴细胞，它们从神经管中适当迁出及其随后的迁移。此外，β-肌动蛋白的缺失会影响钙粘蛋白-11 和 N-钙粘蛋白的功能，这可以部分通过 ROCK 抑制得到缓解，将 Rho-ROCK 信号转导置于与钙粘蛋白-11 的反馈回路中。
