New Type of Mutation Found to Cause Alpha-Thalassemia
Single-nucleotide polymorphism found upstream of coding region
FRIDAY, June 2 (HealthDay News) -- A single mutation that results in the inherited blood disorder alpha-thalassemia lies outside the region where disease-causing mutations usually occur, according to a report in the May 26 issue of Science.
Douglas R. Higgs, D.Sc., from the John Radcliffe Hospital in Oxford, U.K., and colleagues analyzed the alpha-globin gene cluster and the surrounding base-pairs in 148 individuals from Melanesia with alpha-thalassemia.
The researchers found no evidence of deletions or chromosomal rearrangements, there were normal patterns of DNA methylation, and none of the known alpha-thalassemia mutations in the alpha-globin gene cluster on chromosome 16 played a role in the cases. Further analysis through resequencing, chromatin immunoprecipitation, and a tiled oligonucleotide array identified a single-nucleotide polymorphism (SNP) in the region between the alpha-globin gene and upstream regulatory elements. This SNP created a new genetic element that appeared to disrupt the expression of all downstream alpha-like globin genes, according to the authors.
"Thus, our work illustrates a strategy for distinguishing between neutral and functionally important regulatory SNPs, and it also identifies a pathogenic mechanism that could potentially underlie other genetic diseases," Higgs and colleagues conclude.