TDK conference 2017

The primer mitochondrial disorders are caused by the mutation of mitochonrial and nuclear genes coding proteins responsible for the mitochondrial structure and function. The disorder is multisystemic and may affect multiple organs. The inheritance pattern might be dominant, recessive, X-linked and maternal as well. It is also possible, that the same gene can be inherited either dominantly or recessively. Based on different databases, approximatly 1500 genes are responsible for the correct mitochondrila structure and function. Up to date out of these 1500 genes

only 500 are directly linked to different clinical symptoms of mitochondrial disorders. During our work we have studied 51 nuclear genes coding proteins with role in mitochondrial replication, transcription, and translation as well in mitochondrial DNA biogenesis, morphogenesis, and dynamics. according to a systematic literature review the frequency of patogenic alterations in these genes is very high.

Aim: In this study we investigated that the mutations in these 51genes how frequently occured in the Hungarian population and what was the correlation between the detected gene mutation and clinical phenotype.

Patients and Methods: In this study 46 multisystemic mitochondrial patients were enrolled (18 male, 28 female). For all patients the performed muscular biopsy verified the mitochondrial disorder. The DNA was isolated from blood or muscle. The selected 51 genes were sequenced by using next generation target sequencing. Following the primary bioinformatic analysis of the clusters, the variants were mapped onto the human reference genome and turned into annotation to the human genome. During the in silico analysis, we focused on rare (minor allele frequency < 0.05) variants, nonsense, missense and splice site mutations with high biological function impact. Those variants considered patogenic by the in silico analysis were validated by Sanger sequencing and segregation studies were

performed for the family members.

Results: In these 46 patients we found 208 rare nonsense, missense and splice site variants using target NGS. In 3 patients, we found two pathogenic mutations, which are already known from the literature as the genetic cause of mitochondrial diseases. In addition, we have found 10 new rare variants which are under validation currently.

Conclusion: With NGS target sequencing, in 28% of the patients we identified the genetic mutation of the disease. Further analysis of these variants is still in progress.