Population Genetics of Culex tritaeniorhynchus (Diptera: Culicidae) in Türkiye

PURPOSE

Mosquitoes are important vectors of pathogens that can affect humans and animals. Culex tritaeniorhynchus is an important vector of arboviruses such as Japanese encephalitis virus, West Nile virus among various human and animal communities. These diseases are of major public health concern and can have huge economic and health burdens in prevalent countries. Although populations of this important mosquito species have been detected in the Mediterranean and Aegean regions of Türkiye; little is known about its population structure. Our study is to examine the population genetics and genetic composition of Cx. tritaeniorhynchus mosquitoes collected from several localities using cytochrome oxidase subunit I (COI) and the NADH dehydrogenase subunit 5 genes (ND5). This is the first extensive study of Cx. tritaeniorhynchus in the mainland Türkiye with sampling spanning many of provinces.

METHODS

In this study, DNA extraction, amplification of mitochondrial COI and ND5 genes and population genetic analyses were performed on ten geographic populations of Culex tritaeniorhynchus in the Aegean and Mediterranean region of Türkiye.

RESULTS

Between 2019 and 2020, 96 samples were collected from 10 geographic populations in the Aegean and Mediterranean regions; they were molecularly analyzed and 139 sequences (50 sequence for COI and 89 sequence for ND5) were used to determine the population structure and genetic diversity. For ND5 gene region, the samples produced 24 haplotypes derived from 15 variable sites and for COI gene region, 43 haplotypes were derived from 17 variable sites. The haplotype for both gene regions was higher than nucleotide diversity. Haplotype phylogeny revealed two groups present in all populations. AMOVA test results show that the geographical populations were the same for all gene regions. Results suggest that Cx. tritaeniorhynchus is a native population in Türkiye, the species is progressing towards speciation and there is no genetic differentiation between provinces and regions.

CONCLUSION

This study provides useful information on the molecular identifcation and genetic diversity of Cx. tritaeniorhynchus; these results are important to improve mosquito control programs.

Mitochondrial ND5 mutation mediated elevated ROS regulates apoptotic pathway epigenetically in a P53 dependent manner for generating pro-cancerous phenotypes

We have previously observed concomitant events of mutations in mitochondrial and nuclear genes, along with elevated reactive oxygen species (ROS) and differential methylation within the promoters of nuclear genes in tumors and in vitro experiments of tumorigenesis. These observations have made it pertinent to replicate and understand the role of acquired mitochondrial condition in tuning a cell to accomplish a pro-cancerous state. Using a codon optimized vector system for exogenous over-expression and mitochondrial localization; we have characterized here the role of over-expressed wild type mtND5 and one of its non-synonymous somatic mutation, ND5:P265H. The ectopically over-expressed ND5:P265H in mitochondria resulted in a reduced Complex I activity, generation of higher ADP/ATP ratio, reactive oxygen species (ROS) and carbonylation of proteins as compared to mock-transfected cells. Cells over-expressing mtND5 variant produced both peroxide as well as super-oxide ROS; the generation of which was dependent on the functional status of P53; modulating epigenetically the expression of key apoptosis pathway genes. The pro-cancerous phenotypes, of anchorage dependent and independent growth; increased glucose uptake and lactate production, were selectively observed only in P53 non-functional cells over-expressing mutant ND5:P265H. We propose that somatic mutation in mtND5 resulting in down-regulated complex I enzyme activity, elevated ROS and up-regulation of a set of nuclear anti-apoptotic genes epigenetically in the P53 dysfunctional cellular background, has provided a unique understanding of the molecular mechanism of mitochondrial mutation; and the concomitant existence of somatically acquired mitochondrial and nuclear p53 mutations, in cancer progression and promotion.