Genetic variants in autism-related CNTNAP2 impair axonal growth of cortical neurons
Genetic variants in autism-related CNTNAP2 impair axonal growth of cortical neurons
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DOI：
10.1093/hmg/ddy102
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发表时间：
2018-06-01
影响因子：
3.5
通讯作者：
Goutebroze, Laurence
中科院分区：
文献类型：
--
作者：
Canali, Giorgia;Garcia, Marta;Goutebroze, Laurence
CNTNAP2 基因编码细胞粘附糖蛋白 Caspr2，被认为是自闭症谱系障碍 (ASD) 的主要易感基因之一。 ASD 患者中发现了大量罕见的杂合错义 CNTNAP2 变异。然而，它们中的大多数是从未受影响的父母遗传的，因此对其临床意义提出质疑。在本研究中，我们评估了它们在杂合遗传背景下对 Caspr2 神经发育功能的影响。通过对小鼠胚胎进行皮层神经元培养，我们证明 Caspr2 在体外轴突生长中发挥剂量依赖性作用。一个 Cntnap2 等位基因的缺失足以引起轴突生长改变，揭示了一种可能与 ASD 患者中 CNTNAP2 杂合性相关的情况。然后，我们发现两个 ASD 变体 I869T 和 G731S 与 Contactin2/TAG-1 的结合受损，不能挽救轴突生长缺陷。我们发现，通过与野生型 Caspr2 寡聚化，导致蛋白质运输缺陷和保留在内质网中的变异 R1119H 对杂合 Cntnap2 皮质神经元轴突生长具有显性负效应。最后，我们确定了另一个对轴突生长具有显性负效应的变体（N407S），尽管它在膜上定位良好并且与 Contactin2 正确结合。因此，我们的数据确定了 Caspr2 的新神经发育功能，其失调可能导致 ASD 的临床表现，并提供证据表明 CNTNAP2 杂合错义变异可能通过选择性机制导致 ASD 的致病性。
The CNTNAP2 gene, coding for the cell adhesion glycoprotein Caspr2, is thought to be one of the major susceptibility genes for autism spectrum disorder (ASD). A large number of rare heterozygous missense CNTNAP2 variants have been identified in ASD patients. However, most of them are inherited from an unaffected parent, questioning their clinical significance. In the present study, we evaluate their impact on neurodevelopmental functions of Caspr2 in a heterozygous genetic background. Performing cortical neuron cultures from mouse embryos, we demonstrate that Caspr2 plays a dose-dependent role in axon growth in vitro. Loss of one Cntnap2 allele is sufficient to elicit axonal growth alteration, revealing a situation that may be relevant for CNTNAP2 heterozygosity in ASD patients. Then, we show that the two ASD variants I869T and G731S, which present impaired binding to Contactin2/TAG-1, do not rescue axonal growth deficits. We find that the variant R1119H leading to protein trafficking defects and retention in the endoplasmic reticulum has a dominant-negative effect on heterozygous Cntnap2 cortical neuron axon growth, through oligomerization with wild-type Caspr2. Finally, we identify an additional variant (N407S) with a dominant-negative effect on axon growth although it is well-localized at the membrane and properly binds to Contactin2. Thus, our data identify a new neurodevelopmental function for Caspr2, the dysregulation of which may contribute to clinical manifestations of ASD, and provide evidence that CNTNAP2 heterozygous missense variants may contribute to pathogenicity in ASD, through selective mechanisms.