[Effective Viral Delivery of Genetic Constructs to Neuronal Culture for Modeling and Gene Therapy of GNAO1 Encephalopathy].

GNAO1 encephalopathy is an orphan genetic disease associated with early infantile epilepsy, impaired motor control, and severe developmental delay. The disorder is caused by mutations in the GNAO1 gene, leading to dysfunction of the encoded protein Gao1. There is no cure for this disease, and symptomatic therapy is ineffective. Phenotypic heterogeneity highlights the need for a personalized approach for treating patients with a specific clinical variant of GNAO1 and requires the study of the disease mechanism in animal and cell models. Towards this aim, we developed an approach for modeling GNAO1 encephalopathy and testing gene therapy drugs in primary neurons derived from healthy mice. We optimized the delivery of transgenes to Gαo1-expressing neurons using recombinant adeno-associated viruses (rAAV). We assessed the tropism of five neurotropic AAV serotypes (1, 2, 6, 9, DJ) for Gαo1-positive neurons from the whole mouse brain. The DJ serotype showed the highest potential as a reporter delivery vehicle, infecting up to 66% of Gαo1-expressing cells without overt cytotoxicity. We demonstrated that AAV-DJ also provides efficient delivery and expression of genetic constructs encoding normal and mutant Gαo1, as well as short hairpin RNA (shRNA) to suppress endogenous Gnao1 in murine neurons. Our results will further simplify the study of the pathological mechanism for clinical variants of GNAO1, as well as optimize the testing of gene therapy approaches for GNAO1 encephalopathy in cell models.

Detection of Mutations in Mitochondrial DNA by Droplet Digital PCR.

Mutations in mitochondrial DNA (mtDNA) may result in various pathological processes. Detection of mutant mtDNAs is a problem for diagnostic practice that is complicated by heteroplasmy - a phenomenon of the inferring presence of at least two allelic variants of the mitochondrial genome. Also, the level of heteroplasmy largely determines the profile and severity of clinical manifestations. Here we discuss detection of mutations in heteroplasmic mtDNA using up-to-date methods that have not yet been introduced as routine clinical assays. These methods can be used for detecting mutations in mtDNA to verify diagnosis of "mitochondrial disease", studying dynamics of mutant mtDNA in body tissues of patients, as well as investigating structural features of mtDNAs. Original data on allele-specific discrimination of m.11778G>A mutation by droplet digital PCR are presented, which demonstrate an opportunity for simultaneous detection and quantitative assessment of mutations in mtDNAs.