Two exon-skipping mutations as the molecular basis of succinic semialdehyde dehydrogenase deficiency (4-hydroxybutyric aciduria).
Succinic semialdehyde dehydrogenase (SSADH) deficiency, a rare metabolic disorder of 4-aminobutyric acid degradation, has been identified in approximately 150 patients. Affected individuals accumulate large quantities of 4-hydroxybutyric acid, a compound with a wide range of neuropharmacological activities, in physiological fluids. As a first step in beginning an investigation of the molecular genetics of SSADH deficiency, we have utilized SSADH cDNA and genomic sequences to identify two point mutations in the SSADH genes derived from four patients. These mutations, identified by standard methods of reverse transcription, PCR, dideoxy-chain termination, and cycle sequencing, alter highly conserved sequences at intron/exon boundaries and prevent the RNA-splicing apparatus from properly recognizing the normal splice junction. Each family segregated a mutation in a different splice site, resulting in exon skipping and, in one case, a frameshift and premature termination and, in the other case, an in-frame deletion in the resulting protein. Family members, including parents and siblings of these patients, were shown to be heterozygotes for the splicing abnormality, providing additional evidence for autosomal recessive inheritance. Our results provide the first evidence that 4-hydroxybutyric aciduria, resulting from SSADH deficiency, is the result of genetic defects in the human SSADH gene.
Chambliss
K L
KL
Institute of Metabolic Disease, Baylor University Medical Center, Dallas, USA.
Hinson
D D
DD
Trettel
F
F
Malaspina
P
P
Novelletto
A
A
Jakobs
C
C
Gibson
K M
KM
D000445:Aldehyde Oxidoreductases / Q000737:chemistry / Q000172:deficiency* / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002478:Cells, Cultured; D003241:Consanguinity; D005091:Exons; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D006885:Hydroxybutyrates / Q000652:urine*; D007438:Introns; D008214:Lymphocytes / Q000201:enzymology; D008297:Male; D008661:Metabolism, Inborn Errors / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009679:Nuclear Family; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D050644:Succinate-Semialdehyde Dehydrogenase
D006885:Hydroxybutyrates; D011994:Recombinant Proteins; C111420:4-hydroxybutyric acid; D000445:Aldehyde Oxidoreductases; C493643:ALDH5A1 protein, human; D050644:Succinate-Semialdehyde Dehydrogenase