Defective kinesin binding of TUBB2A causes progressive spastic ataxia syndrome resembling sacsinopathy
Defective kinesin binding of TUBB2A causes progressive spastic ataxia syndrome resembling sacsinopathy
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DOI：
10.1093/hmg/ddy096
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发表时间：
2018-06-01
影响因子：
3.5
通讯作者：
Bertini, Enrico
中科院分区：
文献类型：
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作者：
Sferra, Antonella;Fattori, Fabiana;Bertini, Enrico
微管参与基本的细胞过程，包括染色体分离和细胞分裂、迁移和细胞内运输。它们的正常功能是正确的中枢神经系统发育和操作保存所必需的，而编码微管（微管的构成单位）的基因突变是神经发育和神经退行性疾病家族的基础，统称为“微管病”，其特征是由增殖、迁移和功能缺陷导致的广泛的神经元缺陷。在这里，我们将先前未报道的TUBB2A （c.1249G >a, p.D417N）的错义突变与以进行性痉挛性截瘫、外周感觉-运动多发性神经病和共济失调为特征的一种神经元特异性β -微管蛋白同型突变联系起来。Asp（417）是一个高度保守的暴露在溶剂中的残基，介导超家族马达中激酶的结合。通过结构分析预测了与KIF1A（疾病相关TUBB2A突变体突触囊泡前体运输所需的神经元特异性运动蛋白）的结合受损，并在体外实验中得到证实。我们发现，TUBB2A（D417N）的过表达破坏了有丝分裂纺锤体的双极性和形态，并影响了M期的进入和长度。不同于TUBB2A（N247K）和TUBB2A（A248V）这两种先前发现的影响神经发育的突变体，TUBB2（AD417N）保留了组装成微管的能力。与不同的临床和结构影响一致，TUBB2A（A248V）不会显著影响TUBB2A与KIF1A的结合，也不会影响有丝分裂纺锤体双极性。总的来说，我们的数据证明了p.D417N替代的致病作用，这与先前报道的TUBB2A突变不同，并且扩大了与该基因突变相关的表型谱。
Microtubules participate in fundamental cellular processes, including chromosomal segregation and cell division, migration and intracellular trafficking. Their proper function is required for correct central nervous system development and operative preservation, and mutations in genes coding tubulins, the constituting units of microtubules, underlie a family of neurodevelopmental and neurodegenerative diseases, collectively known as 'tubulinopathies', characterized by a wide range of neuronal defects resulting from defective proliferation, migration and function. Here, we causally link a previously unreported missense mutation in TUBB2A (c.1249G>A, p.D417N), encoding one of the neuron-specific beta-tubulin isotype II, to a disorder characterized by progressive spastic paraplegia, peripheral sensory-motor polyneuropathy and ataxia. Asp(417) is a highly conserved solvent-exposed residue at the site mediating binding of kinesin superfamily motors. Impaired binding to KIF1A, a neuron-specific kinesin required for transport of synaptic vesicle precursors of the disease-associated TUBB2A mutant, was predicted by structural analyses and confirmed experimentally in vitro. We show that overexpression of TUBB2A(D417N) disrupts the mitotic spindle bipolarity and morphology and affects the M phase entry and length. Differently from the TUBB2A(N247K) and TUBB2A(A248V), two mutants previously identified to affect neurodevelopment, TUBB2(AD417N) retains the ability to assemble into microtubules. Consistent with the differential clinical and structural impact, TUBB2A(A248V) does not drastically affect TUBB2A binding to KIF1A, nor mitotic spindle bipolarity. Overall, our data demonstrate a pathogenic role of the p.D417N substitution that is different from previously reported TUBB2A mutations and expand the phenotypic spectrum associated with mutations in this gene.