Mutation analysis of methylmalonyl CoA mutase gene exon 2 in Egyptian families: Identification of 25 novel allelic variants

Dina A Ghoraba; Magdy M Mohammed; Osama K Zaki

doi:10.1016/j.mgene.2014.02.001

Mutation analysis of methylmalonyl CoA mutase gene exon 2 in Egyptian families: Identification of 25 novel allelic variants

Meta Gene. 2015 Feb 25:3:71-88. doi: 10.1016/j.mgene.2014.02.001. eCollection 2015 Feb.

Authors

Dina A Ghoraba¹, Magdy M Mohammed², Osama K Zaki¹

Affiliations

¹ Medical Genetics Unit, Children's Hospital, Faculty of Medicine and University Hospitals, Cairo, Egypt.
² Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt.

Abstract

Methylmalonic aciduria (MMA) is an autosomal recessive disorder of methylmalonate and cobalamin (cbl; vitamin B12) metabolism. It is an inborn error of organic acid metabolism which commonly results from a defect in the gene encoding the methylmalonyl-CoA mutase (MCM) apoenzyme. Here we report the results of mutation study of exon 2 of the methylmalonyl CoA mutase (MUT) gene, coding MCM residues from 1 to 128, in ten unrelated Egyptian families affected with methylmalonic aciduria. Patients were presented with a wide-anion gap metabolic acidosis. The diagnosis has established by the measurement of C3 (propionylcarnitine) and C3:C2 (propionylcarnitine/acetylcarnitine) in blood by using liquid chromatography-tandem mass spectrometry (LC/MS-MS) and was confirmed by the detection of an abnormally elevated level of methylmalonic acid in urine by using gas chromatography-mass spectrometry (GC/MS) and isocratic cation exchange high-performance liquid-chromatography (HPLC). Direct sequencing of gDNA of the MUT gene exon 2 has revealed a total of 26 allelic variants: ten of which were intronic, eight were located upstream to the exon 2 coding region, four were novel modifications predicted to affect the splicing region, three were novel mutations within the coding region: c.15G > A (p.K5K), c.165C > A (p.N55K) and c.7del (p.R3EfsX14), as well as the previously reported mutation c.323G > A (p.R108H).

Keywords: Chromatography; Egyptian; Methylmalonic aciduria; Methylmalonyl CoA mutase; Novel mutation; Single nucleotide polymorphism; Tandem mass spectrometry.