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

Biochim Biophys Acta. 1993 Nov 25;1225(1):64-70. doi: 10.1016/0925-4439(93)90123-i.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
  • Base Sequence
  • Cell Fusion
  • Cell Line
  • DNA, Complementary / genetics
  • Genetic Complementation Test
  • Humans
  • Infant, Newborn
  • Ketone Oxidoreductases / chemistry
  • Ketone Oxidoreductases / genetics*
  • Maple Syrup Urine Disease / enzymology
  • Maple Syrup Urine Disease / genetics*
  • Molecular Sequence Data
  • Multienzyme Complexes / chemistry
  • Multienzyme Complexes / genetics*
  • Mutation
  • Phenotype

Substances

  • DNA, Complementary
  • Multienzyme Complexes
  • Ketone Oxidoreductases
  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)