A 17-bp insertion and a Phe215----Cys missense mutation in the dihydrolipoyl transacylase (E2) mRNA from a thiamine-responsive maple syrup urine disease patient WG-34.
We have amplified the cDNA for the transacylase (E2) subunit of the branched-chain alpha-ketoacid dehydrogenase (BCKAD) complex from a thiamine-responsive MSUD cell line (WG-34) by the polymerase chain reaction. Sequencing of the amplified WG-34 cDNA showed a 17-bp insertion (AAATACCTTGTTACCAG) apparently resulting from an aberrant splicing of the E2 gene, and a missense (T----G) mutation that changes Phe215 to Cys in the E2 subunit. The existence of these two mutations was confirmed by probing the amplified E2 cDNA or genomic DNA with allele-specific oligonucleotides. The above results support the thesis that the thiamine-responsive MSUD patient (WG-34) is a compound heterozygote at the E2 locus. The implication of the E2 mutations for the thiamine-responsiveness observed in this patient is discussed.
Fisher
C W
CW
Department of Biochemistry, University of Texas, Southwestern Medical School, Dallas 75235.
Lau
K S
KS
Fisher
C R
CR
Wynn
R M
RM
Cox
R P
RP
Chuang
D T
DT
D000217:Acyltransferases / Q000235:genetics*; D016375:Antisense Elements (Genetics); D001482:Base Composition; D001483:Base Sequence; D002460:Cell Line; D003545:Cysteine; D004251:DNA Transposable Elements; D005091:Exons; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D008375:Maple Syrup Urine Disease / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010649:Phenylalanine; D016133:Polymerase Chain Reaction; D012016:Reference Values; D013831:Thiamine / Q000627:therapeutic use*
D016375:Antisense Elements (Genetics); D004251:DNA Transposable Elements; D010649:Phenylalanine; D000217:Acyltransferases; C033588:dihydrolipoamide acyltransferase; D003545:Cysteine; D013831:Thiamine