Eight novel MUT loss-of-function missense mutations in Chinese patients with isolated methylmalonic academia
- World J Pediatr. 2017 Aug;13(4):381-386. doi: 10.1007/s12519-016-0085-z.
- 1. Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiaotong University School of Medicine, Shanghai, China.
- 2. Department of Pediatric Endocrinology and Genetic Metabolism, Xinhua Hospital, Shanghai Institute for Pediatric Research, Shanghai Jiaotong University School of Medicine, Shanghai, China. [email protected].
- 3. , Room 801 Sci&Edu Bldg, 1665 Kongjiang Rd, Yangpu District, Shanghai, 200092, China. [email protected].
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.