Gene analysis of mennonite maple syrup urine disease kindred using primer-specified restriction map modification

Maple syrup urine disease (MSUD) is an autosomal recessive inherited disease due to a deficiency of any of the subunits, E1α, E1β or E2, of the branched-chain α-ketoacid dehydrogenase complex (BCKDH). A large Mennonite kindred of MSUD has been studied in Pennsylvania, USA. In the present investigation, genomes from 70 members, including 12 patients belonging to eight different Mennonite MSUD pedigrees, were examined for possible abnormalities in the E1α gene of BCKDH, by primer-specified restriction map modification. A T-to-A substitution which generates an asparagine in place of a tyrosine at amino acid 394 of the mature E1α subunit was present in both alleles in all the patients and in a single allele in all obligate carriers and several siblings. We describe a new technique for rapid and easy detection of the mutant gene in this population. These family studies provide additional evidence that Mennonite MSUD is caused by a missense mutation of the E1α gene of BCKDH.