Smith Haley M, Khairallah Stephanie M, Nguyen Ann Hong, Newman-Smith Erin, Smith William C
Department of Molecular, Cellular and Developmental Biology, USA.
Department of Molecular, Cellular and Developmental Biology, USA; Neuroscience Research Institute, University of California, Santa Barbara, CA, 93106, USA.
Dev Biol. 2021 Dec;480:14-24. doi: 10.1016/j.ydbio.2021.08.006. Epub 2021 Aug 15.
Neural tube closure (NTC) is a complex multi-step morphogenetic process that transforms the flat neural plate found on the surface of the post-gastrulation embryo into the hollow and subsurface central nervous system (CNS). Errors in this process underlie some of the most prevalent human birth defects, and occur in about 1 out of every 1000 births. Previously, we discovered a mutant in the basal chordate Ciona savignyi (named bugeye) that revealed a novel role for a T-Type Calcium Channel (Cav3) in this process. Moreover, the requirement for CAV3s in Xenopus NTC suggests a conserved function among the chordates. Loss of CAV3 leads to defects restricted to anterior NTC, with the brain apparently fully developed, but protruding from the head. Here we report first on a new Cav3 mutant in the related species C. robusta. RNAseq analysis of both C. robusta and C. savignyi bugeye mutants reveals misregulation of a number of transcripts including ones that are involved in cell-cell recognition and adhesion. Two in particular, Selectin and Fibronectin leucine-rich repeat transmembrane, which are aberrantly upregulated in the mutant, are expressed in the closing neural tube, and when disrupted by CRISPR gene editing lead to the open brain phenotype displayed in bugeye mutants. We speculate that these molecules play a transient role in tissue separation and adhesion during NTC and failure to downregulate them leads to an open neural tube.
神经管闭合（NTC）是一个复杂的多步骤形态发生过程，它将原肠胚形成后胚胎表面的扁平神经板转化为中空且位于皮下的中枢神经系统（CNS）。这一过程中的错误是一些最常见的人类出生缺陷的根源，大约每1000例出生中就有1例发生。此前，我们在基部脊索动物萨氏海鞘（Ciona savignyi）中发现了一个突变体（命名为突眼），揭示了T型钙通道（Cav3）在此过程中的新作用。此外，非洲爪蟾神经管闭合过程中对CAV3的需求表明脊索动物之间存在保守功能。CAV3的缺失导致仅限于前神经管闭合的缺陷，大脑显然发育完全，但从头部突出。在此，我们首先报道相关物种粗壮海鞘（C. robusta）中的一个新的Cav3突变体。对粗壮海鞘和萨氏海鞘突眼突变体的RNA测序分析揭示了许多转录本的调控异常，包括一些参与细胞间识别和黏附的转录本。特别是其中两个，选择素和富含亮氨酸重复序列的纤连蛋白跨膜蛋白，在突变体中异常上调，在闭合的神经管中表达，当通过CRISPR基因编辑破坏它们时，会导致突眼突变体中出现的脑开放表型。我们推测这些分子在神经管闭合过程中的组织分离和黏附中起短暂作用，未能下调它们会导致神经管开放。
