Heterogeneity of mutations in maple syrup urine disease (MSUD): screening and identification of affected E1 alpha and E1 beta subunits of the branched-chain alpha-keto-acid dehydrogenase multienzyme complex.
Maple syrup urine disease (MSUD) is an autosomal recessive disease caused by a deficiency in subunits of the branched-chain alpha-keto-acid dehydrogenase complex (BCKDH). To characterize the mutations present in five patients with MSUD (four classic and one intermediate), three-step analyses were established: (1), identification of the involved subunit by complementation analysis using three different cell lines derived from homozygotes having E1 alpha, E1 beta or the E2 mutant gene; (2), screening for a mutation site in cDNA of the corresponding subunit by RT-PCR-SSCP and (3), mutant analysis by sequencing the amplified cDNA fragment. Four single-base missense mutations, R115W, Q146K [corrected], A209T and I282T, were detected in the E1 alpha subunit. A single-base missense mutation H156R and three frame-shift mutations to generate stop codons downstream, including an 11-bp deletion of the tandem repeat in exon 1, a single-base (T) deletion and a single-base (G) insertion, were identified in the E1 beta subunit gene. All except one (11-bp deletion in E1 beta (Nobukuni, Y., Mitsubuchi, H., Akaboshi, I., Indo, Y., Endo, F., Yoshioka, A. and Matsuda, I. (1991) J. Clin. Invest. 87, 1862-1866)) were novel mutations. The sites of amino-acid substitution were all conserved in other species. Thus, mutations causing MSUD are heterogenous.
Nobukuni
Y
Y
Department of Pediatrics, Kumamoto University School of Medicine, Japan.
Mitsubuchi
H
H
Hayashida
Y
Y
Ohta
K
K
Indo
Y
Y
Ichiba
Y
Y
Endo
F
F
Matsuda
I
I
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D001483:Base Sequence; D002459:Cell Fusion; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D005816:Genetic Complementation Test; D006801:Humans; D007231:Infant, Newborn; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000235:genetics*; D008375:Maple Syrup Urine Disease / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics*; D009154:Mutation; D010641:Phenotype
D018076:DNA, Complementary; D009097:Multienzyme Complexes; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)