Multi Centric Origin of Hb D-Punjab [β121(GH4)Glu→Gln, GAA>CAA]

Abstract

Hb D-Punjab [β121(GH4)Glu→Gln, GAA>CAA], common in the northern Indian province, is often unexpectedly found in other populations. To study the multi centric origin of this variant which is causing sickle cell disease in association with Hb S [β6(A3)Glu→Val, GAG>GTG], we have examined the haplotype of the Hb D allele in different populations. We studied 43 alleles from south Iran (Hormozgan and Fars provinces) and 14 from Holland and Belgium using high performance liquid chromatography (HPLC), capillary electrophoresis, direct sequencing and/or restriction enzyme analysis. In Iranians, four haplotypes were observed at different frequencies: haplotype I [+ − − – −,+ +] at 67.5%, subhaplotype I' [+ – – – –,– +] at 17.5%, haplotype V [– + – – +,+ +] at 10.0% and haplotype III [– + – + +,+ +] at 5.0%. All European cases were on haplotype I. The occurrence of high Hb D frequencies on a single haplotype in specific regions can be expected if we consider founder effect and genetic drift mechanisms. However, considering that haplotype I is the most common haplotype worldwide, that Hb D-Punjab is reported in different populations on different haplotypes, and that codon β121 is a site on which six different mutations are reported, we may expect to observe Hb D-Punjab in different populations, possibly because of a relatively higher occurrence of de novo mutations, generating unexpected risk from mixtures of allochtonous Hb S and indigenous Hb D-Punjab or vice versa.

Keywords:

• Hb D-Punjab
• Haplotype
• Iran

ACKNOWLEDGMENTS

This study was partially supported by the European Commission grant “ITHANET” no. 026539 and by the Dutch Zon-Mw grant on hemoglobinopathies prevention nr. 21000.0105.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.