Polynesian origins and affinities: globin gene variants in eastern Polynesia

Area of Science:

• Human population genetics
• Molecular anthropology
• Hematogenetics

Background:

• Globin gene copy number variants (CNVs) are crucial in understanding human genetic diversity and disease susceptibility.
• Alpha thalassemia, a common inherited blood disorder, is influenced by variations in alpha-globin genes.
• Zeta-globin genes, while typically silenced early in development, can reveal insights into population history through their CNVs.

Purpose of the Study:

• To investigate the frequency of copy number variants in alpha-, zeta-, and gamma-globin genes among Eastern Polynesians.
• To identify specific genetic markers and their distribution within Polynesian and Melanesian populations.
• To explore the genetic origins and evolutionary history of globin gene variations in Eastern Polynesia.

Main Methods:

• Analysis of copy number variants (CNVs) for alpha-, zeta-, and gamma-globin genes.
• Restriction-enzyme site polymorphism analysis to identify specific haplotypes.
• Comparative genetic analysis with Melanesian and other non-Melanesian populations.

Main Results:

• High frequency of triplicated-zeta-gene chromosomes and a specific alpha thalassemia deletion observed in Eastern Polynesians.
• A unique deletion and a novel restriction-enzyme-site polymorphism associated with zeta zeta zeta chromosomes found exclusively in Melanesians and Polynesians.
• Alpha-globin haplotype analysis revealed similarities to Melanesians, alongside evidence of an additional non-Melanesian genetic influence in Eastern Polynesia.
• Significant frequency fluctuations in several globin gene alleles attributed to genetic drift were detected.

Conclusions:

• Eastern Polynesians possess distinct globin gene CNVs, including alpha thalassemia deletions and triplicated zeta-globin genes, shared with Melanesians.
• The identified genetic markers suggest a complex demographic history involving shared ancestry with Melanesians and potential admixture with other populations.
• Genetic drift has played a significant role in shaping the observed allele frequencies of globin genes in Eastern Polynesian populations.