TNPO2 variants associate with human developmental delays, neurologic deficits, and dysmorphic features and alter TNPO2 activity in Drosophila
TNPO2 variants associate with human developmental delays, neurologic deficits, and dysmorphic features and alter TNPO2 activity in Drosophila
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DOI：
10.1016/j.ajhg.2021.06.019
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发表时间：
2021-09-02
影响因子：
9.8
通讯作者：
Tan, Queenie K-G
中科院分区：
文献类型：
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作者：
Goodman, Lindsey D.;Cope, Heidi;Tan, Queenie K-G
转运蛋白-2(TNPO2)介导多种途径，包括非经典的核质穿梭60货物，如发育和神经元蛋白。我们确定了15名携带TNPO2从头编码变异的个体，他们表现为全球发育迟缓(GDD)、畸形特征、眼科异常和神经学特征。为了评估这些变异的性质，对果蝇进行了功能研究。我们发现Fly dTnpo(与TNPO2同源)在部分神经元中表达。DTnpo对神经元的维持和功能至关重要，因为使用RNAi下调成熟神经元中的dTnpo会扰乱神经元的活动和存活。使用突变等位基因或RNAi改变dTnpo的活性和表达会导致发育缺陷，包括眼睛和翅膀畸形和死亡。这些影响是剂量依赖的，因为更严重的表型与更强的dTnpo丢失相关。有趣的是，在dTnpo上调和TNPO2异位表达的情况下，观察到了相似的表型，表明Transportin活性的丧失和增强导致了发育缺陷。此外，先证者相关变体在异位表达时，与野生型TNPO2相比，可导致或多或少严重的发育异常。被测试的变种的影响似乎与它们在蛋白质中的位置有关。具体地说，属于RAN结合域的那些会引起更严重的毒性，而在酸性环中的那些毒性较小。货物结合结构域中的变体表现出组织依赖效应。综上所述，dTnpo是果蝇发育过程中和神经元中的一个必不可少的基因。此外，TNPO2内的先证者相关从头变体破坏了编码蛋白的功能。因此，TNPO2变异是神经发育异常的原因。
Transportin-2 (TNPO2) mediates multiple pathways including non-classical nucleocytoplasmic shuttling of >60 cargoes, such as developmental and neuronal proteins. We identified 15 individuals carrying de novo coding variants in TNPO2 who presented with global developmental delay (GDD), dysmorphic features, ophthalmologic abnormalities, and neurological features. To assess the nature of these variants, functional studies were performed in Drosophila. We found that fly dTnpo (orthologous to TNPO2) is expressed in a subset of neurons. dTnpo is critical for neuronal maintenance and function as downregulating dTnpo in mature neurons using RNAi disrupts neuronal activity and survival. Altering the activity and expression of dTnpo using mutant alleles or RNAi causes developmental defects, including eye and wing deformities and lethality. These effects are dosage dependent as more severe phenotypes are associated with stronger dTnpo loss. Interestingly, similar phenotypes are observed with dTnpo upregulation and ectopic expression of TNPO2, showing that loss and gain of Transportin activity causes developmental defects. Further, proband-associated variants can cause more or less severe developmental abnormalities compared to wild-type TNPO2 when ectopically expressed. The impact of the variants tested seems to correlate with their position within the protein. Specifically, those that fall within the RAN binding domain cause more severe toxicity and those in the acidic loop are less toxic. Variants within the cargo binding domain show tissue-dependent effects. In summary, dTnpo is an essential gene in flies during development and in neurons. Further, proband-associated de novo variants within TNPO2 disrupt the function of the encoded protein. Hence, TNPO2 variants are causative for neurodevelopmental abnormalities.