Population genetics of Aedes albopictus (Diptera: Culicidae) in its native range in Lao People's Democratic Republic.

BACKGROUND: The Asian tiger mosquito, Aedes (Stegomyia) albopictus (Skuse) is an important worldwide invasive species and can be a locally important vector of chikungunya, dengue and, potentially, Zika. This species is native to Southeast Asia where populations thrive in both temperate and tropical climates. A better understanding of the population structure of Ae. albopictus in Lao PDR is very important in order to support the implementation of strategies for diseases prevention and vector control. In the present study, we investigated the genetic variability of Ae. albopictus across a north-south transect in Lao PDR. METHODS: We used variability in a 1337-bp fragment of the mitochondrial cytochrome c oxidase subunit 1 gene (cox1), to assess the population structure of Ae. albopictus in Lao PDR. For context, we also examined variability at the same genetic locus in samples of Ae. albopictus from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA. RESULTS: We observed very high levels of genetic polymorphism with 46 novel haplotypes in Ae. albopictus from 9 localities in Lao PDR and Thailand populations. Significant differences were observed between the Luangnamtha population and other locations in Lao PDR. However, we found no evidence of isolation by distance. There was overall little genetic structure indicating ongoing and frequent gene flow among populations or a recent population expansion. Indeed, the neutrality test supported population expansion in Laotian Ae. albopictus and mismatch distribution analyses showed a lack of low frequency alleles, a pattern often seen in bottlenecked populations. When samples from Lao PDR were analyzed together with samples from Thailand, China, Taiwan, Japan, Singapore, Italy and the USA, phylogenetic network and Bayesian cluster analysis showed that most populations from tropical/subtropical regions are more genetically related to each other, than populations from temperate regions. Similarly, most populations from temperate regions are more genetically related to each other, than those from tropical/subtropical regions. CONCLUSIONS: Aedes albopictus in Lao PDR are genetically related to populations from tropical/subtropical regions (i.e. Thailand, Singapore, and California and Texas in the USA). The extensive gene flow among locations in Lao PDR indicates that local control is undermined by repeated introductions from untreated sites.

Mutational analysis of metastatic lymph nodes from papillary thyroid carcinoma in adult and pediatric patients.

BACKGROUND: Limited data are available on the analysis of somatic mutations in metastatic lymph nodes in adult and pediatric patients with papillary thyroid carcinomas. METHODS: A total of 92, microdissected, formalin-fixed, paraffin-embedded tissue specimens from 39 patients were analyzed for the presence of somatic mutations utilizing the ThyGenX next-generation sequencing test. RESULTS: Somatic mutations were detected in 67% of papillary thyroid carcinoma specimens. The majority of patients with synchronous and all 6 patients with radioactive iodine-resistant (metachronous) metastatic lymph nodes contained BRAF mutations. Four patients had mutations detected in their metastatic lymph nodes that were not detected in their primary tumors. For the most part, BRAF mutations were seen in adults, and RAS mutations were seen in children. CONCLUSION: Findings of different mutations in metastatic lymph nodes compared with the primary papillary thyroid carcinomas are probably the result of tumor heterogeneity. The presence of the BRAF mutation in metastatic lymph nodes might be responsible for the recurrence of papillary thyroid carcinomas and resistance to radioactive iodine therapy. The good prognosis observed in papillary thyroid carcinomas found in pediatric and young adult patients might be explained by the predominance of RAS rather than BRAF mutations.