Choline Acetyltransferase Mutations Causing Congenital Myasthenic Syndrome: Molecular Findings and Genotype-Phenotype Correlations.
Choline Acetyltransferase Mutations Causing Congenital Myasthenic Syndrome: Molecular Findings and Genotype-Phenotype Correlations.
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DOI：
10.1002/humu.22823
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发表时间：
2015-09
期刊：
影响因子：
3.9
通讯作者：
Maselli RA
中科院分区：
文献类型：
--
作者：
Arredondo J;Lara M;Gospe SM Jr;Mazia CG;Vaccarezza M;Garcia-Erro M;Bowe CM;Chang CH;Mezei MM;Maselli RA
胆碱乙酰转移酶催化胆碱能神经合成乙酰胆碱。人类ChAT的突变会由于ACh的合成受损而导致先天性肌无力综合征(CMS)；这种严重的疾病变体经常与意想不到的潜在致命呼吸暂停发作有关。这种情况的严重程度差异很大，决定这种可变性的分子因素还知之甚少。此外，在双等位基因突变的患者中，很难建立基因-表型相关性。我们分析了七个ChAT突变，p.Val136Met，p.Arg207His，p.Arg186Trp，p.Val194Leu，p.Pro211Ala，p.Arg566Cys和p.Ser694Cys在HEK-293细胞中对磷酸化ChAT的蛋白表达，测定了它们的酶动力学和热不稳定性，并检测了它们的结构变化。三个突变p.Arg207His、p.Arg186Trp和p.Arg566Cys是新发现的，p.Val136Met和p.Arg207His在三个家系中是纯合子，与严重疾病相关。突变体的表征表明，ChAT的总体催化效率下降；特别是那些位于活性中心隧道附近的突变体产生了最严重的破坏表型效应。另一方面，位于远离活性部位和底物结合部位的p.Val136Met对ChAT表达的抑制作用最为明显。总体而言，产生低酶表达和严重动力学效应的ChAT突变与最严重的表型有关。
Choline acetyltransferase catalyzes the synthesis of acetylcholine at cholinergic nerves. Mutations in human CHAT cause a congenital myasthenic syndrome (CMS) due to impaired synthesis of ACh; this severe variant of the disease is frequently associated with unexpected episodes of potentially fatal apnea. The severity of this condition varies remarkably, and the molecular factors determining this variability are poorly understood. Furthermore, genotype–phenotype correlations have been difficult to establish in patients with biallelic mutations. We analyzed the protein expression of seven ChAT mutations, p.Val136Met, p.Arg207His, p.Arg186Trp, p.Val194Leu, p.Pro211Ala, p.Arg566Cys and p.Ser694Cys, in HEK-293 cells to phosphorylated ChAT, determined their enzyme kinetics and thermal instability, and examined their structural changes. Three mutations, p.Arg207His, p.Arg186Trp and p.Arg566Cys, are novel, and p.Val136Met and p.Arg207His are homozygous in three families and associated with severe disease. The characterization of mutants showed a decrease in the overall catalytic efficiency of ChAT; in particular, those located near the active-site tunnel produced the most seriously disruptive phenotypic effects. On the other hand, p.Val136Met is located far from both active and substrate-binding sites produced the most drastic reduction of ChAT expression. Overall, CHAT mutations producing low enzyme expression and severe kinetic effects are associated with the most severe phenotypes.