The genotypic and phenotypic spectrum of pyridoxine-dependent epilepsy due to mutations in ALDH7A1.
Pyridoxine-dependent epilepsy is a disorder associated with severe seizures that may be caused by deficient activity of α-aminoadipic semialdehyde dehydrogenase, encoded by the ALDH7A1 gene, with accumulation of α-aminoadipic semialdehyde and piperideine-6-carboxylic acid. The latter reacts with pyridoxal-phosphate, explaining the effective treatment with pyridoxine. We report the clinical phenotype of three patients, their mutations and those of 12 additional patients identified in our clinical molecular laboratory. There were six missense, one nonsense, and five splice-site mutations, and two small deletions. Mutations c.1217_1218delAT, I431F, IVS-1(+2)T > G, IVS-2(+1)G > A, and IVS-12(+1)G > A are novel. Some disease alleles were recurring: E399Q (eight times), G477R (six times), R82X (two times), and c.1217_1218delAT (two times). A systematic review of mutations from the literature indicates that missense mutations cluster around exons 14, 15, and 16. Nine mutations represent 61% of alleles. Molecular modeling of missense mutations allows classification into three groups: those that affect NAD+ binding or catalysis, those that affect the substrate binding site, and those that affect multimerization. There are three clinical phenotypes: patients with complete seizure control with pyridoxine and normal developmental outcome (group 1) including our first patient; patients with complete seizure control with pyridoxine but with developmental delay (group 2), including our other two patients; and patients with persistent seizures despite pyridoxine treatment and with developmental delay (group 3). There is preliminary evidence for a genotype-phenotype correlation with patients from group 1 having mutations with residual activity. There is evidence from patients with similar genotypes for nongenetic factors contributing to the phenotypic spectrum.
Scharer
Gunter
G
Department of Pediatrics, University of Colorado Denver, Aurora, CO 80045, USA.
Brocker
Chad
C
Vasiliou
Vasilis
V
Creadon-Swindell
Geralyn
G
Gallagher
Renata C
RC
Spector
Elaine
E
Van Hove
Johan L K
JL
D000293:Adolescent; D000328:Adult; D000444:Aldehyde Dehydrogenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000927:Anticonvulsants / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D003120:Colorado; D004252:DNA Mutational Analysis; D002658:Developmental Disabilities / Q000235:genetics; D004827:Epilepsy / Q000188:drug therapy / Q000201:enzymology / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D056726:Genetic Association Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D008297:Male; D008958:Models, Molecular; D009154:Mutation; D010641:Phenotype; D011487:Protein Conformation; D011736:Pyridoxine / Q000627:therapeutic use*; D013329:Structure-Activity Relationship; D016896:Treatment Outcome; D055815:Young Adult
D000927:Anticonvulsants; C089507:ALDH7A1 protein, human; D000444:Aldehyde Dehydrogenase; D011736:Pyridoxine
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