NGS-based mtDNA Profiling Could Reveal Genetic Alterations in Schizophrenia

Schizophrenia is a complex disease with a putative genetic background. It was hypothesized that impaired mitochondrial function due to genetic alterations in mitochondrial DNA (mtDNA) could contribute to neurological conditions, including mental disorders. The aim of the study was to find out possible pathogenic mutations and/or variants in mtDNA potentially related to schizophrenia development.

The study involved 37 patients with paranoid schizophrenia, whose mtDNA profiles were compared to those of 23 healthy controls.

Patients and controls were assessed using PANSS (Positive and Negative Syndrome Scale) and General Health Questionnaire (GHQ), respectively. The entire mtDNA was sequenced by the NGS platform (MiSeq®, Illumina). Bioinformatics data were processed by mtDNA Variant Processor and Analyser (Illumina), mtDNA-Server, and SPSS-17.

A total of 480 mtDNA variants (single nucleotide replacements, point insertions, and deletions) were found. The polymorphic variant m.1811A>G (MT-RNR2) showed the highest frequency in schizophrenia (24.3%), as compared to the controls (4.3%) (p=0.07). Increased frequency was also found mainly in polymorphisms, belonging to complex 1 genes: MT-ND4 (11251G and 11467G), MT-ND3 (10398G), MT-ND1 (4216С), and MT-ND5 (12611G and 13708А), some of which were associated with mitochondrial dysfunction. Two individual mutations were identified in the patients: a pathogenic one - m.11778 A>G (LHON) and a newly identified, potentially pathogenic - m.4115 Т>C (NADH dehydrogenase 1).

Particular mtDNA variants predominantly in complex I, probably serve as a risk genetic background in schizophrenia. The presence of pathogenic mutations in patients with psychotic manifestations expands the clinical scope of mitochondrial diseases and deserves further investigation.