Added: Ignatius Lykes - Date: 05.09.2021 14:39 - Views: 15587 - Clicks: 3930
Investigative Genetics volume 6Article : 11 Cite this article. Metrics details. An Erratum to this article was published on 07 October The Pacific Oceania region was one of the last regions of the world to be settled via human migration. Here we outline a settlement of this region that has given rise to a uniquely admixed population. The current Norfolk Island population has arisen from a small of founders with mixed Caucasian and Polynesian ancestry, descendants of a famous historical event.
Written history details betrayal and murder leading to the founding of Pitcairn Island by European mutineers and the Polynesian women who left Tahiti with them.
Investigation of detailed genealogical records supports historical s. Using genetics, we show distinct maternal Polynesian mitochondrial lineages in the present day population, as well as a European centric Y-chromosome phylogeny. These comprehensively characterise the unique gender-biased admixture of this genetic isolate and further support the historical records relating to Norfolk Island.
Our ificantly refine population genetic studies investigating Polynesian versus Caucasian diversity in the Norfolk Island population and add information that is beneficial to future disease and gene mapping studies. This small island has an eventful history; initially populated and quickly abandoned by seafaring Polynesians, it was rediscovered in by Captain James Cook and used off and on as a British penal colony between and [ 12 ].
Orthographical map showing the location of Norfolk Island and surroundings. The movement of the European mutineers and Tahitian women to Pitcairn Island, and then Norfolk Island is indicated by the dashed red line. The Bounty set for Tahiti inwith the goal of securing and distributing breadfruit for the slave trade. After an unexpectedly long stopover in Tahiti, the majority of the Bounty crew overthrew Captain William Bligh.
Led by Lieutenant Fletcher Christian, 18 mutineers returned to Tahiti. Expecting to be discovered by the British, Christian along with 8 other mutineers, 6 Tahitian men and 18 Tahitian women plus a baby girl fled to the Pitcairn Islands, where the Bounty was burnt to avoid detection and to eliminate the only viable escape route.
Conflict became rife, with numerous murders as well as suicide, leaving all Tahitian men and 7 mutineers dead.
When Ned Young succumbed to respiratory failure inJohn Adams became the sole surviving male on Pitcairn. These three men were the only outsiders to settle permanently on the island and subsequently married into the community. Continual population growth and the concomitant pressure on resources led the British Government to allow the Pitcairn Islanders to settle Norfolk Island. On the 8th Junea total of inhabitants of Pitcairn Island were relocated.
Today Norfolk Island has a population of about permanent residents, with the census reporting that approximately half of the permanent population are descendants of the Pitcairn founders [ 4 ].
ly our group have illustrated the unique genomic properties of the Norfolk Island pedigree [ 56 ], as well as its use in disease gene mapping studies [ 7 — 10 ]; establishing that this population isolate is able to identify both common and rare variants associated with complex phenotypes Norfolk Island women in Norfolk Island to date may be difficult to study in larger but more heterogeneous populations. An important part of this process is identifying and understanding genetic admixture, it is critical to for population substructure when conducting disease gene mapping studies.
In this short report, we detail ificant improvements to our estimates for both maternal and paternal ancestry in the unique population of Norfolk Island. These findings are interesting from a population genetics point of view and in turn highlight a key part of Oceanic history. Our further comprehensively characterise the unique gender-biased admixture of this genetic isolate which is an important consideration when studying complex disease traits. Accurate and detailed historical s have been used by genealogists to create and maintain a well-documented database of the entire Norfolk Island population, spanning all the way back to the original founders.
An updated core pedigree was constructed using this information and genetic information as it became available through genetic studies. Currently, the core pedigree structure contains those individuals that are most closely related and coalesce directly back to the original founders. In this study, we used a representative group of Norfolk Island individuals selected from the pedigree, meaning that they relate back to the original founders, and we have phenotype and genotype information for them. The total of core pedigree members selected was this was adjusted to exclude individuals under the age of 18 yearswhich consisted of males and females.
All individuals gave written informed consent. Ethical approval was granted prior to the commencement of the study by the Griffith University Human Research Ethics Committee ethical approval no: and the project was carried out in accordance with the relevant guidelines, which complied with the Helsinki Declaration for human research. To explore the presence of Polynesian mitochondrial genomes in the Norfolk Island population 23 individuals with direct maternal relationship to the Polynesian founders were selected.
The target amplicon had an expected size of bp for samples without the 9-bp deletion and bp for samples containing the deletion. Genotyping of the 9-bp deletion involved the use of fluorescently labelled primers. Fragment lengths were accurately determined after detection by automated gel capillary electrophoresis.
Each primer pair is tailed with universal M13 sequence and is deed for universal PCR and sequencing conditions. To clean the sequence prior to electrophoresis, 2.
This solution was allowed to incubate at room temperature for 15 min. To facilitate more accurate and high throughput sequencing of complete mitochondrial genomes, we developed an in house method using a combination of long-range PCR and the Life Technologies Ion Torrent Next Generation Sequencing platform. Mitochondrial DNA was enriched and purified before undergoing library preparation. Samples were amplified by long-range PCR, utilising two primer pairs which produce overlapping fragments covering the entire human mitochondrial genome.
Primer sequences used were as follows: fragment 1 from to b. Final reagent concentrations used were 1x Buffer, 0.
Negative controls were included in each PCR run to check for contamination and ensure adequate quality control. Overlapping long-range PCR fragments were pooled together in equimolar amounts for each sample. After pooling and mixing ng was aliquoted for library preparation. Physical shearing using a Biorupter was found to produce a much more even distribution of fragments than an enzymatic approach. The E-Gel SizeSelect system was used to select a target size of bp libraries for use with bp sequencing chemistry. After the final amplification and purification step all libraries were quantified on a Bioanalyser using DNA chips.
Samples for each multiplex were pooled in equimolar amounts and diluted to 26 pM, with 48 samples being plexed into a single sequencing reaction on chips. These FASTA sequences were compared with variant reference information from Phylotree in order to find mitochondrial haplotypes that most closely represented the consensus sequences for that individual.
SNP labelling was performed in accordance with the minimal skeleton Y tree [ 12 ]. Initially mitochondrial DNA mtDNA from 70 females believed to be related to the original founding population was investigated using a restriction-digest assay [ 13 ].
The genetic screen identified 23 individuals with the deletion, with genotypes being confirmed via mitochondrial resequencing variant data is available as Additional file 3. This detected two specific Polynesian haplotypes within the current Norfolk population when aligned against the Cambridge Reference Sequence and another of European origin haplogroup H, Fig.
With the available variation, we were able to detect 2 distinct haplotypes within the 23 B4 individuals; B4a1a1 and B4a1a1a14 the latter has not been ly identified and is labelled in accordance with the latest build of Phylotree [ 16 ]. Interestingly, we note that clade B4a1a1m in phylotree is defined byand [ 16 ]; however, the clade we report B4a1a1a14 shares these variants as well aspotentially suggesting dubious positioning of the clade defined by Building upon this baseline haplogroup information obtained from the 70 females studied, we used genealogical information and available genetic data SNP [ 10 ], and above mtDNA to inform the reconstruction of a pedigree of people with direct ancestral links to the Pitcairn founders.
Six maternal Polynesian founder lineages are highlighted, individuals expected to have these mitochondrial genomes are displayed in colour throughout the tree Fig. It is apparent that of the six observed founding Polynesian women, potentially four separate mitochondrial lineages have persisted and are present in the current day population. We wished to validate and refine this picture at an increased resolution and therefore undertook complete mitochondrial genome sequencing of key members of the Norfolk Island pedigree.
These reveal excellent concordance with the above findings, with The mitochondrial SNPs defining the branching are displayed on the tree. Four separate mitochondrial lineages have persisted and are present in the current day population these are represented by redpinkblue and light blue in the figure. While we were unable to completely resolve two haplotypes indicated in green and yellow in Fig. However, it is possible that as more data becomes available for such Oceanic populations that these haplotypes may be observed.
Y-chromosome lineages, like haplogroup G and haplogroup I1, which are common in North Europe along with haplogroup H also common in India occur elsewhere e. South Asia and are likely a consequence of maritime trade [ 17 ]. A single individual haplotype E individual, P, rs is associated with sub-clade E1b1a1. Not only does this isolated position in the tree compared to the majority of individuals studied suggest that this individual is a recent founder, but the fact that this sub-clade is commonly observed in sub-Saharan Africans [ 1819 ] provides further weight to this possibility.
However, both further sample collection and analysis outside the scope of this project would be required to confirm the likelihood of this. This compelling evidence demonstrates that the vast majority of Y-chromosome Norfolk Island women in Norfolk Island to date within the Norfolk Island pedigree are European in origin. The present study provides increased resolution of Norfolk Island Y-chromosome markers and supports the historical records associated with Pitcairn and subsequently Norfolk Island establishment. Y chromosome phylogeny of male Norfolk Island individuals.
Apart from one individual with haplotype E defined by the P SNP; likely a recent founderthe remaining haplotypes are inferred to be of European origin. The Y chromosome SNPs defining the branching are displayed on Norfolk Island women in Norfolk Island to date tree. There are 2 haplotypes within haplogroup F containing the P and P SNPs which we were unable to get enough resolution to accurately define, these are represented within the F branch and are coloured in yellow and green.
The presented here show excellent concordance with written historical s and greatly improve upon prior findings, refining estimates of sex-dependent admixture bias and specific haplotypic resolution within the Norfolk Island population. Similarly, we have been able to use information obtained from dense SNP arrays to infer the haplotypic status of males based on Y-chromsome genotype data, which is a substantial improvement upon work that was limited to a small of STRs. Overall, these new add much more clarity to the genetic ancestral picture of the Norfolk Island population.
Knowledge of the population substructure caused by the divergence of genetically distinct ancestral populations is important when conducting disease gene mapping studies.
For example, at the very least admixture requires adjustment when performing statistical tests of association within and between populations. The data presented here, unlikewill allow accurate assessment and correction of sex-specific lineages when conducting disease gene mapping studies.
In particular, when performing disease gene mapping studies accurate asment of the mitochondrial haplogroups that distinguish between and within Polynesian and European ancestry subgroups should allow real pathological point variants in the mitochondrial genome to be discerned from those increasing in frequency due to population genetic factors such as genetic drift. The geographic isolation of Norfolk Island, alongside a small of European and Polynesian founders—including the additional 3 European men settling Pitcairn later—have established a unique genetic isolate.
Consequently, extreme gender-biased admixture contributes to this unique genomic structure and provides exciting opportunities for future population genetics and disease gene mapping studies. Edgecombe J.Norfolk Island women in Norfolk Island to date
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