OBJECTIVETo detect the pathogenic mutation in a patient with methylmalonic acidemia using IonTorrent Personal Genome Machine (PGM) and assess the feasibility of such technology for analyzing complex monogenic diseases.

METHODSPeripheral blood sample was collected from the patient. Genomic DNA was isolated using a standard method and subjected to targeted sequencing using an Ion Ampliseq Inherited Disease Panel. DNA fragment was ligated with a barcoded sequencing adaptor. Template preparation, emulsion PCR, and Ion Sphere Particles enrichment were carried out using the Ion One Touch system. Data from the PGM runs were processed using Ion Torrent Suite 3.2 software to generate sequence reads. All variants were filtered against dbSNPl37. DNA sequences were visualized with an Integrated Genomics Viewer.

RESULTSAfter data analysis and database filtering, a previously reported nonsense mutation, c.586C>T (p.R196X), and a novel mutation c.898C>T (p.R300X) were identified in the MMAA gene in this patient. Both mutations were verified by conventional Sanger sequencing.

CONCLUSIONPathogenic MMAA mutations have been identified in a patient with methylmalonic acidemia. This new-generation targeted sequencing on the PGM sequencers can be applied for genetic diagnosis of hereditary diseases.