“Mutation Analysis for Five Palestinian Families Affected by Isolated Congenital Methylmalonic Acidemia”

Abstract

Background: Isolated Methylmalonic acidemia (MMA) is a heterogeneous autosomal-recessive metabolic disorder caused 60% by mutations in the vitamin B12-dependent enzyme methylmalonyl-CoA mutase (MUT). Shortage of this apoenzyme causes MMA. It is an organic acid metabolism aberration that affects systemic metabolic homeostasis, and might cause mental retardation, or even lead to neonatal death. To date, nearly 250 different mutations have been identified in MUT gene. v Materials & Methods: Using 250K Nsp Affymetrix SNP arrays, we finely mapped the MUT gene as candidate in the four consanguineous families. Exons and exon-intron boundaries of the MUT gene were analyzed by polymerase chain reaction and direct Sanger sequencing. Cosegregation analysis was performed to confirm the mutation’s pathogenicity in all families. Haplotype analysis was done in order to determine the origin of the Missense mutation, N219Y. mRNA splicing analysis was done to determine the influence of the splicing mutation IVS8+3 a > g on the mRNA level. A screening was taken place in AlUbeidiya and Wad-Rahal villages. v Results: A homozyogous missense mutation, N219Y, in the MUT gene was identified in three unrelated families from Al-Ubeidiya village, and IVS8+3 a > g was identified in two families from Wad Rahal. Haplotype analysis revealed that the spread of the N219Y among the three families has a founder effect. The mRNA splicing analysis confirmed that exon8 is totally skipped. We further investigated the carrier frequency of N219Y mutation in Al-Ubeidiya village. Conclusion: This is the first Palestinian study to carry mutation analysis of the gene responsible for MMA. This will provide a molecular diagnostic aid for differential diagnosis of MMA and could be applied for carrier detection and prenatal diagnosis among the Palestinian families at risk of MMA. The definitive diagnosis allows a specific treatment. v Keywords: Isolated Methylmalonic academia, MUT gene, Heterogeneous, Haplotype analysis.