TRNA-Leu (UUR) gene haplotypes observed in canine mammary gland tumours and its deleterious effect assessment according to the comparative analysis with TRNL1 human gene

The aetiology and pathogenesis of many canine tumours are likely to be similar to cancers found in humans. This study aimed to present a plausible link between changes in tRNA-Leu (UUR) gene and the carcinogenesis process in dogs with mammary gland tumours. The whole mitochondrial DNA (mtDNA) isolated from blood and tumour tissues of 13 dogs with malig-nant mammary gland tumours was sequenced. The conducted analyses showed two polymor-phisms: m.2678_2679insG and m.2683G>A, located in tRNA-Leu (UUR) gene. We compared the reference sequences of human and canine mtDNA with the use of alignment algorithms in order to find similarities. The homology between human TRNL1 and canine tRNA Leu (UUR) gene was 84%. After resequencing of the whole mitochondrial DNA genome with the use of NGS technology, two polymorphisms in two haplotypes were identified: m.2683G>A (observed in 18 out of 27 samples) and m.2678_2679insG (27 out of 27 samples). The polymorphism m.2683G>A corresponded with deleterious change at m.3243A>G, which is linked with MELAS (Mitochondrial Encephalomyopathy, Lactis Acidose, Stroke-like episodes) syndrome and with different types of cancers in humans as well. The comparative analysis of TRNL1 and tRNA Leu (UUR) led us to hypothesise that the polymorphisms m.2678_2679insG and m.2683G>A might influence on dog’s condition and might be linked with tumorigenesis as it was observed in humans.