Origins of Sickle Cell

Increasing fetal hemoglobin in people with homozygous sickle cell alleviates all symptoms of SCD.
The Google map shows four independent genetic origins, or haplotypes, of SCD in different regions (ellipses) and the subsequent migrations of populations (white arrows). The solid white arrow is to signify the forced migration of Western Africa peoples as slaves to the Western Hemisphere. The four haplotypes (Se = Senegal, Be = Benin, Bantu, and Arab-India) all have the sickle cell mutation in exactly the same gene location, but other genetic differences associated with the haplotypes result in differences in the severity of SCD. The Arab-India group has a second mutation that keeps a fetal hemoglobin (HbF) gene active after birth, such that HbF is up to 45% of the total Hb including sickle hemoglobin (HbS). People of the Arab-India haplotype with 30% or more HbF have no clinical manifestations of SCD, revealing that increased HbF can offer a “cure.” Decreasing HbS and increasing HbF by using gene regulation therapy is the basis of SCCF’s cure.

Globe image of Africa and Asia is copyrighted by Google Earth and is used with permission.