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Mutation analysis in glutaric aciduria type I
J Zschocke1, E Quak, P Guldberg
1Department of Neuropaediatrics and Metabolic Diseases, Philipps University, Marburg, Germany.
Insights
Glutaric aciduria type 1 (GA1) diagnosis is improved with a new denaturing gradient gel electrophoresis (DGGE) method. This technique efficiently identifies mutations in the GCDH gene for molecular diagnosis of GA1.
Area of Science:
- Biochemistry
- Genetics
- Pediatric Neurology
Background:
- Glutaric aciduria type 1 (GA1) is a genetic metabolic disorder causing infant brain damage.
- Diagnosis is challenging due to variable urinary metabolite excretion.
- Glutaryl-CoA dehydrogenase (GDH) deficiency underlies GA1.
Purpose of the Study:
- To develop and validate a rapid, efficient denaturing gradient gel electrophoresis (DGGE) method for molecular diagnosis of GA1.
- To identify mutations in the glutaryl-CoA dehydrogenase (GCDH) gene for routine diagnostic use.
Main Methods:
- Denaturing gradient gel electrophoresis (DGGE) was used to analyze the GCDH gene.
- Molecular diagnosis was performed on patients with confirmed GDH deficiency and clinical suspicion of GA1.
- GCDH gene haplotypes were determined using polymorphic markers.
Main Results:
- DGGE identified mutations in 48 patients with confirmed GDH deficiency.
- Thirty-eight different GCDH gene mutations were found, with 21 being novel.
- The common R402W mutation was prevalent in European patients; 14 mutations occurred at CpG sites.
Conclusions:
- DGGE offers a sensitive, rapid, and cost-effective method for GA1 molecular diagnosis.
- This technique is valuable when enzyme analyses are unavailable or impractical.
- The study highlights the genetic heterogeneity of GA1 and the utility of DGGE in its diagnosis.
Abstract:
Glutaric aciduria type 1 (GA1), resulting from the genetic deficiency of glutaryl-CoA dehydrogenase (GDH), is a relatively common cause of acute metabolic brain damage in infants. Encephalopathic crises may be prevented by carnitine supplementation and diet, but diagnosis can be difficult as some patients do not show the typical excretion of large amounts of glutaric and 3-hydroxyglutaric acids in the urine. We present a rapid and efficient denaturing gradient gel electrophoresis (DGGE) method for the identification of mutations in the glutaryl-CoA dehydrogenase (GCDH) gene that may be used for the molecular diagnosis of GA1 in a routine setting. Using this technique, we identified mutations on both alleles in 48 patients with confirmed GDH deficiency, while no mutations were detected in other patients with clinical suspicion of GA1 but normal enzyme studies. There was a total of 38 different mutations; 27 mutations were found in single patients only, and 21 mutations have not been previously reported. Fourteen mutations involved hypermutable CpG sites. The commonest GA1 mutation in Europeans is R402W, which accounts for almost 40% of alleles in patients of German origin. GCDH gene haplotypes were determined through the analysis of polymorphic markers in all families, and three CpG mutations were associated with different haplotypes, possibly reflecting independent recurrence. The high sensitivity of the DGGE method allows the rapid and cost efficient diagnosis of GA1 in instances where enzyme analyses are not available or feasible, despite the marked heterogeneity of the disease.