G. Martinez

Ethylmalonic Aciduria Is Associated with an Amino Acid Variant of Short Chain Acyl-Coenzyme A Dehydrogenase

Ethylmalonic aciduria is a common biochemical finding in patients with inborn errors of short chain fatty acid β-oxidation. The urinary excretion of ethylmalonic acid (EMA) may stem from decreased oxidation by short chain acyl-CoA dehydrogenase (SCAD) of butyryl-CoA, which is alternatively metabolized by propionyl-CoA carboxylase to EMA. We have recently detected a guanine to adenine polymorphism in the SCAD gene at position 625 in the SCAD cDNA, which changes glycine 209 to serine (G209S). The variant allele (A625) is present in homozygous and in heterozygous form in 7 and 34.8% of the general population, respectively. One hundred and thirty-five patients from Germany, Denmark, the Czech Republic, Spain, and the United Sates were selected for this study on the basis of abnormal EMA excretion ranging from 18 to 1185 mmol/mol of creatinine (controls <18 mmol/mol of creatinine). Among them, we found a significant overrepresentation of the variant allele. Eighty-one patients (60%) were homozygous for the A625 allele, 40 (30%) were heterozygous, and only 14 (10%) harbored the wild-type allele (G625) in homozygous form. By overexpressing the wild-type and variant protein (G209S) in Escherichia coli and COS cells, we showed that the folding of the variant protein was slightly compromised in comparison to the wild-type and that the temperature stability of the tetrameric variant enzyme was lower than that of the wild type. Taken together, the overrepresentation and the biochemical studies indicate that the A625 allele confers susceptibility to the development of ethylmalonic aciduria.

A Survey of the Newborn Populations in Belgium, Germany, Poland, Czech Republic, Hungary, Bulgaria, Spain, Turkey, and Japan for the G985 Variant Allele with Haplotype Analysis at the Medium Chain Acyl-CoA

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an inborn error of fatty acid metabolism. It is one of the most frequent genetic metabolic disorders among Caucasian children. The G985 allele represented 90% of all the variant alleles of the MCAD gene in an extensive series of retrospective studies. To study the distribution of the G985 allele, newborn blood samples from the following countries were tested: 3000 from Germany (1/116), 1000 each from Belgium (1/77), Poland (1/98), Czech Republic(1/240), Hungary (1/168), Bulgaria (1/91), Spain (1/141), Turkey (1/216), and 500 from Japan (none). The frequency is shown in parentheses. The haplotype ofG985 alleles in 1 homozygote and 57 heterozygote samples were then analyzed using two intragenic MCAD gene polymorphisms (TaqI andGT-repeat). The result indicated that only 1 of the 10 known haplotypes was associated with the G985 mutation, suggesting thatG985 was derived originally from a single ancestral source. We made a compilation of the G985 frequencies in these countries and those in nine other European countries studied previously. The G985 distribution was high in the area stretching from Russia to Bulgaria in the east and in all northern countries in western and middle Europe, but low in the southern part of western and middle Europe. The incidence among ethnic Basques appeared to be low. This distribution pattern and the fact that allG985 alleles belong to a single haplotype suggest thatG985 mutation occurred later than the ΔF508 mutation of the CFTR, possibly in the neolithic or in a later period, and was brought into Europe by IndoEuropean-speaking people. The panEuropean distribution of the G985 allele, including Slavic countries from which patients with MCAD deficiency have rarely been detected, indicates the importance of raising the level of awareness of this disease.

High risk of medium chain acyl-coenzyme a dehydrogenase deficiency among gypsies

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is recognized as the most common hereditary defect of fatty acid oxidation in humans. Death is the outcome of the first attack in about 25% of cases. A point mutation (Ala to Gly at position 985) of the MCAD gene represents more than 90% of alleles causing MCAD deficiency. The frequency of this allelic variant exhibits considerable geographical variations. In Spain, where the few diagnosed patients are mostly of Gypsy origin, the frequency is low as occurs in other Southern European countries (1 heterozygote among 200 individuals). Here we have analyzed the frequency of the G985 allele among Spanish gypsies. Heterozygotes were detected at a frequency of 1/17, with a 95% confidence interval ranging from 1/11 to 1/39. This represents the highest G985 rate described so far and calls for preventive measures, such as selective screening in this population.