8 种新型 MUT 失活功能错义突变导致中国孤立性甲基丙二酸血症患者发病。
Eight novel MUT loss-of-function missense mutations in Chinese patients with isolated methylmalonic academia.
机构信息
Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiaotong University School of Medicine, Shanghai, China.
, Room 801 Sci&Edu Bldg, 1665 Kongjiang Rd, Yangpu District, Shanghai, 200092, China.
出版信息
World J Pediatr. 2017 Aug;13(4):381-386. doi: 10.1007/s12519-016-0085-z. Epub 2017 Jan 19.
BACKGROUND
Isolated methylmalonic acidemia is a rare autosomal recessive metabolic disorder mostly caused by mutations in the methylmalonyl coenzyme A mutase (MCM) gene (MUT). This study aimed to verify whether missense mutations in MUT in Chinese patients affect the stability and enzymatic activity of MCM.
METHODS
Eight Chinese patients were identified with novel mutations. Plasmids carrying the wild-type and mutated MUT cDNA were constructed and transfected into HEK293T cells for functional analyses. The expression and activity of MCM were determined by western blot and ultra-performance liquid chromatography, respectively.
RESULTS
All patients had high levels of blood propionylcarnitine and urinary methylmalonyl acid. By the end of the study, two patients were lost to follow-up, three died, and three survived with mental retardation. Compared to the wild-type protein, the expression levels of all missense mutations of in vitro MCM protein were decreased (P<0.05) except those for I597R, and the MCM activity of the mutations was reduced in a permissive assay.
CONCLUSIONS
The missense mutations L140P, A141T, G161V, W309G, I505T, Q514K, I597R and G723D affected the stability and enzymatic activity of MCM, indicating that they had a disease-causing capacity.
背景
孤立性甲基丙二酸血症是一种罕见的常染色体隐性遗传代谢紊乱，主要由甲基丙二酰辅酶 A 变位酶（MCM）基因（MUT）的突变引起。本研究旨在验证 MUT 中的错义突变是否会影响 MCM 的稳定性和酶活性。
方法
鉴定了 8 名中国患者存在新的突变。构建携带野生型和突变型 MUT cDNA 的质粒，并转染 HEK293T 细胞进行功能分析。通过 Western blot 和超高效液相色谱法分别测定 MCM 的表达和活性。
结果
所有患者的血液丙酰肉碱和尿甲基丙二酸水平均升高。研究结束时，2 名患者失访，3 名患者死亡，3 名患者存活但伴有智力障碍。与野生型蛋白相比，除 I597R 外，所有体外 MCM 蛋白错义突变的表达水平均降低（P<0.05），且突变体的 MCM 活性在许可检测中降低。
结论
错义突变 L140P、A141T、G161V、W309G、I505T、Q514K、I597R 和 G723D 影响 MCM 的稳定性和酶活性，表明它们具有致病能力。
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