Alpha-thalassaemia and globin gene rearrangements in French Polynesia

The -α3.7III subtype of α+-thalassemia was identified in China

OBJECTIVE

The 3.7 kb deletion (-α^3.7) in the α-globin cluster, which characterizes α⁺-thalassemia, has been reported to have a carrier rate of 4.78% in southern China. Three -α^3.7 subtypes have been identified worldwide. However, the -α^{3.7 III} subtype has not previously been identified in China. Herein, we reported identification of the -α^{3.7 III} subtype in a Chinese patient.

METHODS

We used gap-PCR and a liquid chip system to detect α-thalassemia mutations. Multiple ligation-dependent probe amplification was performed to detect the large deletion. We finally used Sanger sequencing and single molecule real-time sequencing to characterize and confirm the genotype.

RESULTS

The proband, characterized as -α^{3.7 III} heterozygous, showed microcytosis and hypochromic red cells, with a mean corpuscular volume of 78 fL and mean corpuscular hemoglobin of 25.4 pg. The proband's mutation was inherited from her father, who had normal blood parameters.

CONCLUSION

We first identified the -α^{3.7 III} subtype in China. Consequently, all -α^3.7 subtypes have now been identified in the Chinese population. Therefore, attention should be paid to -α^{3.7 III} in clinical prenatal diagnosis, given that commonly used methods such as gap-PCR may lead to misdiagnosis or missed diagnosis.

Walking backwards into the future: the need for a holistic evolutionary approach in Pacific health research

CONTEXT

The Pacific region has had a complex human history. It has been subject to multiple major human dispersal and colonisation events, including some of the earliest Out-of-Africa migrations, the so-called Austronesian expansion of people out of Island Southeast Asia, and the more recent arrival of Europeans. Despite models of island isolation, evidence suggests significant levels of interconnectedness that vary in direction and frequency over time. The Pacific Ocean covers a vast area and its islands provide an array of different physical environments with variable pathogen loads and subsistence opportunities. These diverse environments likely caused Pacific peoples to adapt (both genetically and culturally) in unique ways. Differences in genetic background, in combination with adaptation, likely affect their susceptibility to non-communicable diseases.

OBJECTIVES

Here we provide an overview of some of the key issues in the natural and human history of the Pacific region which are likely to impact human health. We argue that understanding the evolutionary and cultural history of Pacific peoples is essential for the generation of testable hypotheses surrounding potential causes of elevated disease susceptibility among Pacific peoples.

Association between a common immunoglobulin heavy chain allele and rheumatic heart disease risk in Oceania

The indigenous populations of the South Pacific experience a high burden of rheumatic heart disease (RHD). Here we report a genome-wide association study (GWAS) of RHD susceptibility in 2,852 individuals recruited in eight Oceanian countries. Stratifying by ancestry, we analysed genotyped and imputed variants in Melanesians (607 cases and 1,229 controls) before follow-up of suggestive loci in three further ancestral groups: Polynesians, South Asians and Mixed or other populations (totalling 399 cases and 617 controls). We identify a novel susceptibility signal in the immunoglobulin heavy chain (IGH) locus centring on a haplotype of nonsynonymous variants in the IGHV4-61 gene segment corresponding to the IGHV4-61*02 allele. We show each copy of IGHV4-61*02 is associated with a 1.4-fold increase in the risk of RHD (odds ratio 1.43, 95% confidence intervals 1.27–1.61, P=4.1 × 10⁻⁹). These findings provide new insight into the role of germline variation in the IGH locus in disease susceptibility.

Rheumatic heart disease (RHD) is a chronic auto-inflammatory reaction to group A streptococcal infection, and frequently occurs in individuals from the South Pacific. This study finds a novel association between an immunoglobulin heavy chain allele and risk of RHD in Pacific Islanders and South Asians.