Zurel, H. | Search bioRxiv

bioRxiv2022

Characterization of the Y Chromosome in Newfoundland and Labrador: Evidence of a Founder Effect

The population of Newfoundland and Labrador (NL) is largely derived from settlers who migrated primarily from England and Ireland in the 1700-1800s. Previously described as an isolated founder population, based on historical and demographic studies, data on the genetic ancestry of this population remains fragmentary. Here we describe the largest investigation of patrilineal ancestry in NL. To determine the paternal genetic structure of the population, 1,110 Y chromosomes from an NL based cohort were analyzed using 5,761 Y-specific markers. We identified 160 distinct paternal haplotypes, the majority of which (71.4%) belong to the R1b haplogroup. When NL is compared with global reference populations, the haplotype composition and frequencies of the NL paternal lineages primarily resemble the English and Irish ancestral source populations. There is also evidence for genetic contributions from Basque, French, Portuguese, and Spanish fishermen and early settlers that frequented NL. The population structure shows geographical and religious clustering that can be associated with the settlement of ancestral source populations from England and Ireland. For example, the R1b-M222 haplotype, seen in people of Irish descent, is found clustered in the Irish-settled Southeast region of NL. The clustering and expansion of Y haplotypes in conjunction with the geographical and religious clusters illustrate that limited subsequent in-migration, geographic isolation and societal factors have contributed to the genetic substructure of the NL population and its designation as a founder population.

genomics↗

bioRxiv2022

Newfoundland and Labrador: A mosaic founder population of an Irish and British diaspora from 300 years ago.

The founder population of Newfoundland and Labrador (NL) is a unique genetic resource, in part due to geographic and cultural isolation, where historical records describe a migration of European settlers primarily from Ireland and England to NL in the 18th and 19th centuries. Whilst its historical isolation, and increase prevalence of certain monogenic disorders, have been appreciated, the fine-scale genetic structure and ancestry of the population has not been well described. Understanding the genetic background on which functional, disease causing, genetic variation resides on would aid informed genetic mapping efforts in the Province. Here, we leverage dense genome-wide SNP data on 1,807 NL individuals to reveal fine-scale genetic structure in NL that is clustered around coastal communities and correlated with Christian denomination. We show that the majority of NL European ancestry can be traced back to the south-east and south-west of Ireland and England, respectively. We date a substantial population size bottleneck approximately 10-15 generations ago in NL, associated with increased haplotype sharing and autozygosity. Our results elucidate novel insights into the population history of NL and demonstrate evidence of a population conducive to further genetic studies and biomarker discovery. Significance StatementNewfoundland and Labrador (NL) has been identified as a founder population, though evidence of its magnitude and subsequent isolation is unclear. Here, analysis of 1,807 NL individuals demonstrates population structure associated with geographical isolation in coastal communities and religious denomination (Catholic or Protestant Christian). Further, NL European ancestry primarily descends from settlers from south-east Ireland and south-west England. This history is associated with increased sharing of longer haplotypes in NL, and NL-specific drift in some communities more than others, providing strong evidence of a founder event occurring about 10-15 generations ago. This study elucidates the detailed population structure of NL and shows enrichment for otherwise low frequency functional variants due to genetic drift useful for potential future biomarker discovery studies.

genetics↗