Molecular analysis of methylmalonic acidemia: Identification of novel mutations in the methylmalonyl-CoA mutase gene with decreased level of mutant mRNA
- Tohoku Univ. School of Medicine, Sendai (Japan)
Deficiency of methylmalonyl-CoA mutase (MCM) results in methylmalonic acidemia, which is inherited as an autosomal recessive trait and clinically characterized by metabolic ketoacidosis. Previous studies of Caucasian and African American patients identified seven MCM mutations, and we also detected four missense substitutions (Ala197Thr, Val368Asp, Arg369His and Val669Glu). However, mutations with decreased level of MCM mRNA, which accounts for at least 25% of mutations among Caucasian patients, have not been reported. Our study on eight Japanese patients indicated that 13 of 16 mutant alleles (81%) showed decreased level of MCM mRNA, suggesting that these {open_quotes}low message{close_quotes} alleles are likely to be common contributors to MCM deficiency. Reverse transcription/polymerase chain reaction (RT-PCR) of MCM mRNA followed by analysis on a fluorescent fragment analyzer indicated that the level of these mutant mRNAs was less than 1% controls. We were able to amplify such mutant mRNAs by nested PCR and directly determine the primary structure. Sequence analysis revealed three novel mutations: a G-to-T substitution at nucleotide position 425, a 2 bp deletion at nt 769 and 770, and a G-to-T substitution at nt 326. The first mutation (G425T) resulted in the substitution of a termination codon for glutamic acid at amino acid position 117. The analysis of 17 Japanese patients revealed the presence of G425T in 7 alleles (21%), suggesting a relatively high incidence of the mutation among Japanese patients. This observation is in sharp contrast to previous reports describing diverse heterogeneity of MCM mutations among Caucasians. Our report is the first to identify MCM mutations that decrease the stability of MCM mRNA. Amplification of trace amount of mRNA followed by sequencing analysis may provide useful tool for identifying such mutations.
- OSTI ID:
- 134271
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-1007
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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