The Y831C Mutation of the POLG Gene in Dementia.

BACKGROUND

The POLG gene encodes the catalytic subunit of DNA polymerase γ, which is crucial for mitochondrial DNA (mtDNA) repair and replication. Gene mutation alters the stability of mtDNA and is associated with several clinical presentations, such as dysarthria and ophthalmoplegia (SANDO), progressive external ophthalmoplegia (PEO), spinocerebellar ataxia and epilepsy (SCAE), Alpers syndrome, and sensory ataxic neuropathy. Recent evidence has also indicated that POLG mutations may be involved in some neurodegenerative disorders, although systematic screening is currently lacking.

METHODS

To investigate the frequency of POLG gene mutations in neurodegenerative disorders, we screened a group of 33 patients affected by neurodegenerative diseases, including Parkinson's disease, some atypical parkinsonisms, and dementia of different types.

RESULTS

Mutational analysis revealed the presence of the heterozygous Y831C mutation in two patients, one with frontotemporal dementia and one with Lewy body dementia. The allele frequency of this mutation reported by the 1000 Genomes Project in the healthy population is 0.22%, while in our group of patients, it was 3.03%, thus showing a statistically significant difference between the two groups.

CONCLUSIONS

Our results may expand the genotype-phenotype spectrum associated with mutations in the POLG gene and strengthen the hypothesis of a pathogenic role of the Y831C mutation in neurodegeneration.