Abstract
The high risk of metabolic disease traits in Polynesians may be partly explained by elevated prevalence of genetic variants involved in energy metabolism. The genetics of Polynesian populations has been shaped by island hoping migration events which have possibly favoured thrifty genes. The aim of this study was to sequence the mitochondrial genome in a group of Maoris in an effort to characterise genome variation in this Polynesian population for use in future disease association studies. We sequenced the complete mitochondrial genomes of 20 non-admixed Maori subjects using Affymetrix technology. DNA diversity analyses showed the Maori group exhibited reduced mitochondrial genome diversity compared to other worldwide populations, which is consistent with historical bottleneck and founder effects. Global phylogenetic analysis positioned these Maori subjects specifically within mitochondrial haplogroup - B4a1a1. Interestingly, we identified several novel variants that collectively form new and unique Maori motifs – B4a1a1c, B4a1a1a3 and B4a1a1a5. Compared to ancestral populations we observed an increased frequency of non-synonymous coding variants of several mitochondrial genes in the Maori group, which may be a result of positive selection and/or genetic drift effects. In conclusion, this study reports the first complete mitochondrial genome sequence data for a Maori population. Overall, these new data reveal novel mitochondrial genome signatures in this Polynesian population and enhance the phylogenetic picture of maternal ancestry in Oceania. The increased frequency of several mitochondrial coding variants makes them good candidates for future studies aimed at assessment of metabolic disease risk in Polynesian populations.
Highlights
Scientific evidence from linguistics, archaeology and genetics indicates that the mitochondrial sequence data for a Polynesian (Maori) population of New Zealand (NZ) represents the final link in a long chain of island-hopping voyages by Polynesians, which began in Taiwan and stretched through Melanesia and across the Pacific Islands over a period of 5–6000 years (Figure 1)
Sequence variation was identified by comparison against the revised Cambridge Reference Sequence (CRS) [13], which belongs to haplogroup H
This study provides the first complete mitochondrial sequence data for a Polynesian (Maori) population, and as such allows a rare opportunity to enhance the maternal phylogeny in Oceania as well as explore the mitochondrial genome for potential metabolic risk genes in Polynesians
Summary
Scientific evidence from linguistics, archaeology and genetics indicates that the Maori population of New Zealand (NZ) represents the final link in a long chain of island-hopping voyages by Polynesians, which began in Taiwan and stretched through Melanesia and across the Pacific Islands over a period of 5–6000 years (Figure 1). Around 800 years ago one or more small groups of voyagers arrived in NZ from Tahiti, via the Cook Islands. This event marked the last of the great human migrations and the creation of an isolated founder population. Obesity and type 2 diabetes mellitus [2,3,4,5] Given that these traits are partially influenced by genetic factors it is likely that genes involved in energy metabolism play a role in disease risk [6]. These mitochondrial variants may have increased in frequency in Maoris via genetic drift as a consequence of repeated founder events and subsequent population bottlenecks
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