A Neurexin2aa deficiency results in axon pathfinding defects and increased anxiety in zebrafish
A Neurexin2aa deficiency results in axon pathfinding defects and increased anxiety in zebrafish
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DOI：
10.1093/hmg/ddaa260
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发表时间：
2020-12-01
影响因子：
3.5
通讯作者：
Winkler, Christoph
中科院分区：
文献类型：
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作者：
Koh, Angela;Tao, Shijie;Winkler, Christoph
神经毒素是控制突触活动的突触前跨膜蛋白，是自闭症谱系障碍的危险因素。斑马鱼是行为研究的流行模型，有六个神经毒素基因，但它们在胚胎发生和行为中的功能仍然很大程度上未知。我们之前曾报道过，在脊髓性肌萎缩症模型中，nrxn2a 在运动神经元 (MN) 中存在异常剪接和特异性失调。在这项研究中，我们通过 CRISPR/Cas9 生成了 nrxn2aa(-/-) 突变体，以了解 nrxn2aa 在斑马鱼神经肌肉接头 (NMJ) 的功能，并确定其缺陷对成年行为的影响。来自杂合父母的纯合突变胚胎在 MN 的轴突生长或突触发生方面没有表现出明显的缺陷。相比之下，母系合子（MZ）nrxn2aa（-/-）突变体表现出广泛分支的轴突和有缺陷的MN，表明母体提供的nrxn2aa在MN发育中具有细胞自主作用。对 NMJ 的分析显示，突变幼虫 MN 中的选择点扩大，突触前和突触后末端的共定位减少，表明突触形成受损。当突变转录本强烈上调时，严重的早期 NMJ 缺陷在晚期胚胎中部分恢复。然而，最终，诱导的缺陷导致成年 MZ 突变体出现肌肉萎缩症状。合子纯合突变体发育正常，但在成年阶段表现出焦虑增加。总之，我们的数据证明了母体 nrxn2aa 在 NMJ 突触建立中的重要作用，而合子 nrxn2aa 表达对于突触维持似乎是可有可无的。此外，可行的 nrxn2aa(-/-) 突变体还可以作为研究焦虑样行为的增加如何影响其他缺陷的新模型。
Neurexins are presynaptic transmembrane proteins that control synapse activity and are risk factors for autism spectrum disorder. Zebrafish, a popular model for behavioral studies, has six neurexin genes, but their functions in embryogenesis and behavior remain largely unknown. We have previously reported that nrxn2a is aberrantly spliced and specifically dysregulated in motor neurons (MNs) in models of spinal muscular atrophy. In this study, we generated nrxn2aa(-/-) mutants by CRISPR/Cas9 to understand nrxn2aa function at the zebrafish neuromuscular junction (NMJ) and to determine the effects of its deficiency on adult behavior. Homozygous mutant embryos derived from heterozygous parents did not show obvious defects in axon outgrowth or synaptogenesis of MNs. In contrast, maternal-zygotic (MZ) nrxn2aa(-/-) mutants displayed extensively branched axons and defective MNs, suggesting a cell-autonomous role for maternally provided nrxn2aa in MN development. Analysis of the NMJs revealed enlarged choice points in MNs of mutant larvae and reduced co-localization of pre- and post-synaptic terminals, indicating impaired synapse formation. Severe early NMJ defects partially recovered in late embryos when mutant transcripts became strongly upregulated. Ultimately, however, the induced defects resulted in muscular atrophy symptoms in adult MZ mutants. Zygotic homozygous mutants developed normally but displayed increased anxiety at adult stages. Together, our data demonstrate an essential role for maternal nrxn2aa in NMJ synapse establishment, while zygotic nrxn2aa expression appears dispensable for synapse maintenance. The viable nrxn2aa(-/-) mutant furthermore serves as a novel model to study how an increase in anxiety-like behaviors impacts other deficits.