title: Mutation and biochemical analysis of patients belonging to the cblB complementation class of vitamin B12-dependent methylmalonic aciduria.
abstract: Methylmalonic aciduria, cblB type (OMIM 251110) is an inborn error of vitamin B(12) metabolism that occurs due to mutations in the MMAB gene. MMAB encodes the enzyme ATP:cobalamin adenosyltransferase, which catalyzes the synthesis of the coenzyme adenosylcobalamin required for the activity of the mitochondrial enzyme methylmalonyl CoA mutase (MCM). MCM catalyzes the isomerization of methylmalonyl CoA to succinyl CoA. Deficient MCM activity results in methylmalonic aciduria and a susceptibility to life-threatening acidotic crises. The MMAB gene was sequenced from genomic DNA from a panel of 35 cblB patients, including five patients previously investigated. Nineteen MMAB mutations were identified, including 13 previously unknown mutations. These included 11 missense mutations, two duplications, one deletion, four splice-site mutations, and one nonsense mutation. None of these mutations was identified in 100 control alleles. Most of the missense mutations (9/11) were clustered in exon 7; many of these affected amino acid residues that are part of the probable active site of the enzyme. One previously described mutation, c.556C >T (p.R186W), was particularly common, accounting for 33% of pathogenic alleles. It was seen almost exclusively in patients of European background and was typically associated with presentation in the first year of life.
authors.affiliation: Department of Human Genetics, McGill University, Montreal, Que., Canada.
authors.forename: Jordan P
authors.initials: JP
authors.lastname: Lerner-Ellis
authors.forename: Abigail B
authors.initials: AB
authors.lastname: Gradinger
authors.forename: David
authors.initials: D
authors.lastname: Watkins
authors.forename: Jamie C
authors.initials: JC
authors.lastname: Tirone
authors.forename: Amélie
authors.initials: A
authors.lastname: Villeneuve
authors.forename: C Melissa
authors.initials: CM
authors.lastname: Dobson
authors.forename: Alexandre
authors.initials: A
authors.lastname: Montpetit
authors.forename: Pierre
authors.initials: P
authors.lastname: Lepage
authors.forename: Roy A
authors.initials: RA
authors.lastname: Gravel
authors.forename: David S
authors.initials: DS
authors.lastname: Rosenblatt
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008661:Metabolism, Inborn Errors / Q000145:classification / Q000235:genetics* / Q000378:metabolism* / Q000652:urine; D008764:Methylmalonic Acid / Q000378:metabolism / Q000652:urine*; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D014805:Vitamin B 12 / Q000378:metabolism*
chemical_list: D008764:Methylmalonic Acid; D019883:Alkyl and Aryl Transferases; C019920:cob(I)alamin adenosyltransferase; D014805:Vitamin B 12