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.
