HB F-MAURITIUS [(A)GAMMA-23-(B5)-ALA-DELETED] - EVIDENCE FOR AN IDENTICAL HOTSPOT FOR DELETIONS IN THE VARIOUS BETA-LIKE GENES

Hemoglobin (Hb) F-Mauritius, a new (A) gamma chain variant, was identi fied from a dried blood spot collected from a heelprick during neonata l screening for the main hemoglobinopathies. This hemoglobin is the fi rst gamma chain variant having a one residue deletion: it concerns ala nine at position gamma 23. Hb F-Mauritius is therefore the counterpart of Hb Freiburg, an unstable variant of the beta chain in which the va line residue that occupies position beta 23 is deleted The structural modification of Hb F-Mauritius was characterized by miniaturized prote in chemistry methods, including sequence determination by mass spectro metry measurements. Hb Freiburg was used he a control in several exper imental procedures. The hypothesis that a similar mechanism for deleti on has occurred in Hb F-Mauritius and in Hb Freiburg is supported by t he high percentage of homology observed between the beta and gamma glo bin genes. In addition, the first exon of the beta-globin has been rec ognized as a hotspot for deletion: several beta-thalassemic mutations, or abnormal Hbs, with deletions of short nucleotide sequences map in this region.