Kariwiga, J. | Search bioRxiv

bioRxiv2024

Denisovan admixture facilitated environmental adaptation in Papua New Guinean populations

Neandertals and Denisovans, having inhabited distinct regions in Eurasia and possibly Oceania for over 200,000 years, experienced ample time to adapt to diverse environmental challenges these regions presented. Among present-day human populations, Papua New Guineans (PNG) stand out as one of the few carrying substantial amounts of both Neandertal and Denisovan DNA, a result of past admixture events with these archaic human groups. This study investigates the distribution of introgressed Denisovan and Neandertal DNA within two distinct PNG populations, residing in the highlands of Mt Wilhelm and the lowlands of Daru Island. These locations exhibit unique environmental features, some of which may parallel the challenges that archaic humans once confronted and adapted to. Our results show that Denisovan-like haplotypes exhibit increased levels of population differentiation between PNG highlanders and lowlanders. The highly differentiated haplotypes, more common among highlanders, reside in genomic areas linked to brain development genes. Conversely, those more frequent in lowlanders overlap with genes enriched in immune response processes. Furthermore, Denisovan-like haplotypes displayed pronounced signatures of diversification within the major histocompatibility complex. Our findings suggest that Denisovan DNA has provided a valuable source of genetic variation to PNG genomes that facilitated adaptive responses to environmental challenges.

genomics↗

bioRxiv2022

Positive selection in the genomes of two Papua New Guinean populations at distinct altitude levels

Highlanders and lowlanders of Papua New Guinea (PNG) have faced distinct environmental conditions. These environmental differences lead to specific stress on PNG highlanders and lowlanders, such as hypoxia and environment-specific pathogen exposure, respectively. We hypothesise that these constraints induced specific selective pressures that shaped the genomes of both populations. In this study, we explored signatures of selection in newly sequenced whole genomes of 54 PNG highlanders and 74 PNG lowlanders. Based on multiple methods to detect selection, we investigated the 21 and 23 genomic top candidate regions for positive selection in PNG highlanders and PNG lowlanders, respectively. To identify the most likely candidate SNP driving selection in each of these regions, we computationally reconstructed allele frequency trajectories of variants in each of these regions and chose the SNP with the highest likelihood of being under selection with CLUES. We show that regions with signatures of positive selection in PNG highlanders genomes encompass genes associated with the hypoxia-inducible factors pathway, brain development, blood composition, and immunity, while selected genomic regions in PNG lowlanders contain genes related to immunity and blood composition. We found that several candidate driver SNPs are associated with haematological phenotypes in the UK biobank. Moreover, using phenotypes measured from the sequenced Papuans, we found that two candidate SNPs are significantly associated with altered heart rates in PNG highlanders and lowlanders. Furthermore, we found that 16 of the 44 selection candidate regions harboured archaic introgression. In four of these regions, the selection signal might be driven by the introgressed archaic haplotypes, suggesting a significant role of archaic admixture in local adaptation in PNG populations.

evolutionary biology↗