DNA carrier testing and newborn screening for maple syrup urine disease in Old Order Mennonite communities

Genet Test Mol Biomarkers. 2010 Apr;14(2):205-8. doi: 10.1089/gtmb.2009.0107.


Maple syrup urine disease (MSUD) is an inherited metabolic disorder caused by mutations in the branched chain alpha-keto acid dehydrogenase complex. Worldwide incidence of MSUD is 1:225,000 live births. However, within Old Order Mennonite communities, the incidence is 1:150 live births and results from a common tyrosine to asparagine substitution (Y438N) in the E1alpha subunit of branched chain alpha-keto acid dehydrogenase. We developed a new DNA diagnostic assay utilizing TaqMan technology and compared its efficacy, sensitivity, and duration with an existing polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Carrier testing was performed by both TaqMan technology and PCR-RFLP on DNA isolated from buccal swabs of 160 individuals as well as from buccal swabs and blood spots of nine at-risk newborns; assay time, sensitivity, and reliability were also evaluated. The TaqMan assay, like the PCR-RFLP assay, accurately determined Y438N E1alpha allele status. However, the TaqMan assay appeared (1) more sensitive than the PCR-RFLP assay, requiring 10-fold less DNA (10 ng) to reliably determine genotype status and (2) faster, reducing the assay time required for diagnosis from approximately 12 to 5 h. TaqMan technology allowed more rapid DNA diagnoses of MSUD in the neonate, thereby reducing the likelihood of neurological impairment while enhancing health and prognosis for affected infants.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / genetics
  • Alleles
  • Amino Acid Substitution
  • Base Sequence
  • DNA / genetics
  • DNA Mutational Analysis
  • DNA Primers / genetics
  • Ethnicity / genetics
  • Female
  • Founder Effect
  • Genetic Carrier Screening / methods*
  • Humans
  • Infant, Newborn
  • Male
  • Maple Syrup Urine Disease / diagnosis*
  • Maple Syrup Urine Disease / enzymology
  • Maple Syrup Urine Disease / genetics*
  • Neonatal Screening / methods*
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length


  • DNA Primers
  • DNA
  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)