Genetic analysis of three genes causing isolated methylmalonic acidemia: identification of 21 novel allelic variants.
Isolated methylmalonic aciduria (MMA) is an inborn error of metabolism due to the impaired isomerization of l-methylmalonyl-CoA to succinyl-CoA. This reaction is catalyzed by the mitochondrial protein methylmalonyl-CoA mutase (MCM, EC 5.4.99.2), an adenosylcobalamin-dependent enzyme. Four different forms of isolated MMA have been described: mut MMA associated with defects in the MCM apoenzyme, and phenotypically divided into two subtypes mut- and mut0 MMA, and three different defects involved in the synthesis of the active form of the cofactor adenosylcobalamin, termed cbl MMA, and classified into three different complementation groups cblA, cblB, and cblH associated with defects in the MMAA and MMAB genes and with an unidentified protein, respectively. In this work we describe the genetic analysis of 25 MMA patients, mainly from Spain. Using biochemical and cellular approaches our patients have been classified, identifying 13 mut MMA, 7 cblA, 2 cblB, and 3 noncblA, noncblB deficient patients. cDNA and genomic DNA sequence analysis of the MUT, MMAA, and MMAB genes have allowed us to identify 27 different changes, 21 novel ones. Among the missense mutations identified in the MUT gene only one, the c.970G>A (p.A324T) variant located in the substrate binding domain is likely a mut- mutation. The remaining missense mutations c.326A>G (p.Q109R), c.983T>C (p.L328P), c.1846C>T (p.R616C), and c.1850T>G (p.L617R) are probably mut0. In the MMAA patients analyzed, frameshift mutations are prevalent. We have explored the genotype-phenotype correlation for this clinically heterogeneous disease.
Martínez
Maria Angeles
MA
Centro de Biología Molecular Severo Ochoa, CSIC-UAM,Universidad Autónoma, Madrid, Spain.
Rincón
Ana
A
Desviat
Lourdes R
LR
Merinero
Begoña
B
Ugarte
Magdalena
M
Pérez
Belén
B
D000138:Acidosis / Q000235:genetics*; D019883:Alkyl and Aryl Transferases / Q000235:genetics*; D000483:Alleles; D000592:Amino Acid Metabolism, Inborn Errors / Q000235:genetics*; D000595:Amino Acid Sequence; D014644:Genetic Variation; D006801:Humans; D026901:Membrane Transport Proteins / Q000235:genetics*; D008765:Methylmalonyl-CoA Mutase / Q000235:genetics*; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation
C497512:MMAA protein, human; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D019883:Alkyl and Aryl Transferases; C019920:cob(I)alamin adenosyltransferase; D008765:Methylmalonyl-CoA Mutase