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Impaired Function of a Rare Mutation in the MMUT Gene Causes Methylmalonic Acidemia in a Chinese Patient.

ABSTRACT: Methylmalonic acidemia (MMA) is an autosomal recessive metabolic disorder mainly caused by mutations in the methylmalonyl coenzyme A mutase (MCM) gene (MMUT) and leads to the reduced activity of MCM. In this study, a 3-year-old girl was diagnosed with carnitine deficiency secondary to methylmalonic acidemia by tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GS/MS). Whole-exome sequencing (WES) was performed on the patient and identified two compound heterozygous mutations in MMUT: c.554C>T (p. S185F) and c.729-730insTT (p. D244Lfs ^∗ 39). Bioinformatics analysis predicted that the rare missense mutation of c.554C>T would be damaging. Moreover, this rare mutation resulted in the reduced levels of MMUT mRNA and MMUT protein. Collectively, our findings provide a greater understanding of the effects of MMUT variants and will facilitate the diagnosis and treatment of patients with MMA.

SUBMITTER: Dai S

PROVIDER: S-EPMC9337929 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature

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Impaired Function of a Rare Mutation in the <i>MMUT</i> Gene Causes Methylmalonic Acidemia in a Chinese Patient.

Dai Siyu S Yang Yanting Y Li Yaqian Y Liu Hongqian H

Genetics research 20220722

Methylmalonic acidemia (MMA) is an autosomal recessive metabolic disorder mainly caused by mutations in the methylmalonyl coenzyme A mutase (MCM) gene (<i>MMUT</i>) and leads to the reduced activity of MCM. In this study, a 3-year-old girl was diagnosed with carnitine deficiency secondary to methylmalonic acidemia by tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GS/MS). Whole-exome sequencing (WES) was performed on the patient and identified two compound heterozygous ...[more]

PMID: 35919035

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Project description:ObjectivesMethylmalonic acidemia (MMA) is a rare inborn genetic disorder that is characterized by increased levels of methylmalonic acid in blood plasma and urine. Isolated methylmalonic acidemia is one of the most common types of MMA and is caused by mutations in the gene encoding methyl-malonyl coenzyme A mutase (MMUT). In this study, we investigated the possible mechanisms underlying the symptoms of isolated MMA in a patient by molecular analysis.MethodsPCR amplification and Sanger sequencing analysis was performed to identify variants in the MMUT gene in the proband and his family. Furthermore, minigene constructs were generated to validate the splicing defects in the MMUT gene variant identified in the proband.ResultsThe 3-year-old patient was admitted to the hospital with symptoms of MMA, including fever, convulsions, and vomiting. He showed metabolic acidosis, high levels of methylmalonic acid in blood and urine, and normal blood homocysteine levels. Genetic analysis demonstrated that the patient was a compound heterozygous carrier of two variants in the MMUT gene: a missense c.278G > A variant that has already been reported in a patient with the severe mut⁰ phenotype; and a novel splice site variant c.2125-2A > G. RT-PCR analysis showed that, while the novel variant clearly alters splicing, a minor amount of a full-length transcript is generated, suggesting that a wild-type protein may be produced although at a lower quantitative level. The patient's condition improved after treatment with vitamin B12. Serious complications were not reported during follow-up at age 5.ConclusionsWe identified a novel splice site variant that partially disrupts normal splicing of the MMUT pre-mRNA. Production of a reduced amount of full-length transcript is responsible for the mild clinical phenotype observed in this patient. Functional studies have proven useful in exploring the genotype-phenotype association and in providing guidance for the genetic diagnosis of MMA.

Dataset Information

Impaired Function of a Rare Mutation in the MMUT Gene Causes Methylmalonic Acidemia in a Chinese Patient.

Publications

Impaired Function of a Rare Mutation in the <i>MMUT</i> Gene Causes Methylmalonic Acidemia in a Chinese Patient.

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