MOLECULAR DIAGNOSIS OF MEDIUM-CHAIN ACYL-COA DEHYDROGENASE-DEFICIENCYBY OLIGONUCLEOTIDE LIGATION ASSAY

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is a recessively inherited defect in the mitochondrial beta-oxidation of fatty acids. A single nucleotide change, the A(985)-->G transition, in the MCAD gen e accounts for similar to 90% of all the disease-causing mutations in the patients. We have used PCR to amplify a segment of the human MCAD gene and typed the allelic sequence variation at base 985 by a colorim etric oligonucleotide ligation assay (OLA). PCR/OLA provides a techniq ue that permits differentiation of the homozygotes, heterozygotes, and normals for the A(985)-->G allele in the MCAD gene. Genotyping of 190 8 random Finnish DNA samples by OLA identified 10 carriers of the muta nt allele, but no homozygotes were found. The calculated carrier frequ ency for the A(985)-->G mutation was 1:191 (95% confidence limits, 1:1 18-1:501), and the calculated frequency for the A(985)-->G homozygotes was 1:147 000 (95% confidence limits, 1:56 000-1:1 004 000).