Molecular investigations of mitochondrial deletions: evaluating the usefulness of different genetic tests.

Deletions in mitochondrial DNA are a common cause of mitochondrial disorders. The molecular diagnosis of mtDNA deletions for years was based on Southern hybridization later replaced by PCR methods such as PCR with primers specific for a particular deletion (mainly the so-called common deletion of 4977 bp) and long PCR. In order to evaluate the usefulness of MLPA (Multiplex Ligation-dependent Probe Amplification) in molecular diagnosis of large scale mtDNA deletions we compare four diagnostic methods: Southern hybridization, PCR, long-PCR and MLPA in a group of 16 patients with suspected deletions. Analysis was performed on blood, muscle and in one case hepatic tissue DNA. The MLPA was not able to confirm all the deletions detected by PCR methods, but due to its relative ease of processing, minimal equipment, low costs and the additional possibility to detect frequent point mtDNA mutations in one assay it is worth considering as a screening method. We recommend to always confirm MLPA results by PCR methods.