Functional Analysis of A Novel Splicing Mutation in The Mutase Gene of Two Unrelated Pedigrees

Objective: Methylmalonic acidura (MMA) is a rare autosomal recessive inborn error of metabolism. In this study we present a novel nucleotide change in the mutase (MUT) gene of two unrelated Iranian pedigrees and introduce the methods used for its functional analysis. Materials and Methods: Two probands with definite diagnosis of MMA and a common novel variant in the MUT were included in a descriptive study. Bioinformatic prediction of the splicing variant was done with different prediction servers. Reverse transcription- polymerase chain reaction (RT-PCR) was done for splicing analysis and the products were analyzed by sequencing. Results: The included index patients showed elevated levels of propionylcarnitine (C3). Urine organic acid analysis confirmed the diagnosis of MMA, and screening for mutations in the MUT revealed a novel C to G variation at the 3´ splice acceptor site in intron 12. In silico analysis suggested the change as a mutation in a conserved sequence. The splicing analysis showed that the C to G nucleotide change at position -3 in the acceptor splice site can lead to retention of the intron 12 sequence. Conclusion: This is the first report of a mutation at the position -3 in the MUT intron 12 (c.2125-3C > G). The results suggest that the identified variation can be associated with the typical clinical manifestations of MMA.