Journal of Inherited Metabolic Disease

, Volume 33, Supplement 3, pp 191–198

Functional characterization of the novel intronic nucleotide change c.288+9C>T within the BCKDHA gene: understanding a variant presentation of maple syrup urine disease

  • Paula Fernández-Guerra
  • Rosa Navarrete
  • Kara Weisiger
  • Lourdes R. Desviat
  • Seymour Packman
  • Magdalena Ugarte
  • Pilar Rodríguez-Pombo
Research Report

DOI: 10.1007/s10545-010-9077-7

Cite this article as:
Fernández-Guerra, P., Navarrete, R., Weisiger, K. et al. J Inherit Metab Dis (2010) 33: 191. doi:10.1007/s10545-010-9077-7

Abstract

Mutations in any of the three different genes—BCKDHA, BCKDHB, and DBT—encoding for the E1α, E1β, and E2 catalytic components of the branched-chain α-ketoacid dehydrogenase complex can cause maple syrup urine disease (MSUD). Disease severity ranges from the classic to the mildest variant types and precise genotypes, mostly based on missense mutations, have been associated to the less severe presentations of the disease. Herein, we examine the consequences at the messenger RNA (mRNA) level of the novel intronic alteration c.288+9C>T found in heterozygous fashion in a BCKDHA variant MSUD patient who also carries the nucleotide change c.745G>A (p.Gly249Ser), previously described as a severe change. Direct analysis of the processed transcripts from the patient showed—in addition to a low but measurable level of normal mRNA product—an aberrantly spliced mRNA containing a 7-bp fragment of intron 2, which could be rescued when the patient’s cells were treated with emetine. This aberrant transcript with a premature stop codon would be unstable, supporting the possible activation of nonsense-mediated mRNA decay pathway. Consistent with this finding, minigene splicing assays demonstrated that the point mutation c.288+9C>T is sufficient to create a cryptic splice site and cause the observed 7-bp insertion. Furthermore, our results strongly suggest that the c.288+9C>T allele in the patient generates both normal and aberrant transcripts that could sustain the variant presentation of the disease, highlighting the importance of correct genotyping to establish genotype–phenotype correlations and as basis for the development of therapeutic interventions.

Copyright information

© SSIEM and Springer 2010

Authors and Affiliations

  • Paula Fernández-Guerra
    • 1
    • 3
  • Rosa Navarrete
    • 1
    • 3
  • Kara Weisiger
    • 2
  • Lourdes R. Desviat
    • 1
    • 3
  • Seymour Packman
    • 2
  • Magdalena Ugarte
    • 1
    • 3
  • Pilar Rodríguez-Pombo
    • 1
    • 3
  1. 1.Centro de Diagnóstico de Enfermedades Moleculares, Dpto. Biol. Mol., Centro Biología Molecular-SO UAM-CSICUniversidad Autónoma de Madrid, Campus CantoblancoMadridSpain
  2. 2.Division of Medical Genetics, Department of PediatricsUniversity of California–San Fancisco (UCSF)San FranciscoUSA
  3. 3.Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER)Instituto de Salud Carlos IIIMadridSpain