Complete mtDNA sequencing reveals mutations m.9185T>C and m.13513G>A in three patients with Leigh syndrome

Abstract

The most common mitochondrial disorder in children is Leigh syndrome, which is a progressive and genetically heterogeneous neurodegenerative disorder caused by mutations in nuclear genes or mitochondrial DNA (mtDNA). In the present study, a novel and robust method of complete mtDNA sequencing, which allows amplification of the whole mitochondrial genome, was tested. Complete mtDNA sequencing was performed in a cohort of patients with suspected mitochondrial mutations. Patients from Latvia and Lithuania (n = 92 and n = 57, respectively) referred by clinical geneticists were included. The de novo point mutations m.9185T>C and m.13513G>A, respectively, were detected in two patients with lactic acidosis and neurodegenerative lesions. In one patient with neurodegenerative lesions, the mutation m.9185T>C was identified. These mutations are associated with Leigh syndrome. The present data suggest that full-length mtDNA sequencing is recommended as a supplement to nuclear gene testing and enzymatic assays to enhance mitochondrial disease diagnostics.

Impact of the m.13513G>A Variant on the Functions of the OXPHOS System and Cell Retrograde Signaling

“…We hypothesize there might be a threshold between 50% and 70% heteroplasmy for the m.13513G>A variant that affects the ability to produce energy through complex I-dependent oxygen consumption and the need for compensation through complex II-dependent respiration. This would be supported by the fact that the affected patient, described by us in detail previously, carries 60% heteroplasmy for the m.13513G>A variant [ 28 ].…”

“…On days 14–30 after fusion, successful cybrid clones growing in this medium were isolated. The presence of exogenous mtDNA or specific mtDNA haplogroups in each cybrid was confirmed by Sanger sequencing of isolated DNA [ 28 ].…”

“…Isolated complex I deficiency represents the most common mitochondrial respiratory chain defect, involved in mitochondrial disorders, and it has been associated with heterogeneous manifestations, including phenotypic overlaps of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS), Leigh syndrome, and Leber’s hereditary optic neuropathy (LHON) [ 27 ]. A previous report from our laboratory described a patient with Leigh syndrome harboring the mtDNA variant m.13513G>A in the MT-ND5 gene at 60% heteroplasmy level [ 28 ]. The present study was designed to investigate the effect of this m.13513G>A variant on the oxidative phosphorylation (OXPHOS) system and cell retrograde signaling.…”

Roles of mitochondria in neutrophils

“…Besides nuclear genome-encoded genes of mitochondrial components, mitochondrial DNA also encodes genes that are associated with many diseases, such as Leigh syndrome (102)(103)(104), NARP (neuron, ataxia, and retinitis pigmentosa) syndrome (105), and Leber hereditary optic neuropathy (106,107). Thus, mitochondrial gene editing is critical for studying the roles of mitochondria in human neutrophils.…”