Evidence of recent natural selection on the Southeast Asian deletion (--(SEA)) causing α-thalassemia in South China

BMC Evol Biol. 2013 Mar 11:13:63. doi: 10.1186/1471-2148-13-63.


Background: The Southeast Asian deletion (--(SEA)) is the most commonly observed mutation among diverse α-thalassemia alleles in Southeast Asia and South China. It is generally argued that mutation --(SEA), like other variants causing hemoglobin disorders, is associated with protection against malaria that is endemic in these regions. However, little evidence has been provided to support this claim.

Results: We first examined the genetic imprint of recent positive selection on the --(SEA) allele and flanking sequences in the human α-globin cluster, covering a genomic region spanning ~410 kb, by genotyping 28 SNPs in a Chinese population consisting of 76 --(SEA) heterozygotes and 138 normal individuals. The pattern of linkage disequilibrium (LD) and the long-range haplotype test revealed a signature of positive selection. The network of inferred haplotypes suggested a single origin of the --(SEA) allele.

Conclusions: Thus, our data support the hypothesis that the --(SEA) allele has been subjected to recent balancing selection, triggered by malaria.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Asian People / genetics*
  • Chromosomes, Human, Pair 16*
  • Gene Deletion
  • Haplotypes
  • Hemoglobins / genetics*
  • High-Throughput Nucleotide Sequencing
  • Humans
  • Malaria / genetics*
  • Polymorphism, Single Nucleotide
  • Recombination, Genetic
  • Selection, Genetic*
  • alpha-Thalassemia / genetics*


  • Hemoglobins