Maple syrup urine disease in the Austronesian aboriginal tribe Paiwan of Taiwan: a novel DBT (E2) gene 4.7 kb founder deletion caused by a nonhomologous recombination between LINE-1 and Alu and the carrier-frequency determination.

Maple syrup urine disease (MSUD) is an autosomal recessive inborn error disorder derived from the accumulation of the branched-chain amino acids (BCAAs) leucine, isoleucine and valine. Either the E1alpha, E1beta or DBT (E2) genes are responsible for this neurometabolic disease. Here, we report the identification and characterization of a novel E2 gene 4.7 kb deletion as a rare nonhomologous recombination of the long interspersed nuclear elements 1 (LINE-1) in intron 10 and the Alu in the 3' UTR of the E2 gene from three classic MSUD patients of the Austronesian aboriginal tribe Paiwan in Taiwan. The E2 gene 4.7 kb deletion accounted for five out of six alleles in the three unrelated Paiwanese MSUD patients, indicating a founder effect. Carrier-frequency study revealed one deleted heterozygote out of 101 normal Paiwanese. As the nine Taiwanese Austronesian aboriginal tribes share a common origin, this E2 4.7 kb deletion may be preserved in some of the other Austronesian aboriginal tribes of Taiwan. This is the first comprehensive genetics study of MSUD in the Austronesian tribal groups as well as in Taiwan.