Could the expression of Hb Bart's at birth be attributed to several genetics factors?

Abstract

Raised Hb Bart’s at birth was used for long time as an alpha-thalassemiamarker. However, the same α-globin genotype could give variable Hb Bart’s levels. Herein, we wonder about this variability origin testing genetic determinantsdescribed earlier as involved in gamma-globin chain over-expression 21 children of 3 years old that carried Hb Bart’s at birth and for which Alphathal genotype was explored earlier were tested for gamma-globin chain overexpression determinants : beta-thalassemia mutations, gamma globin gene promoters, polymorphism C->T at -158 of gamma-G gene were tested respectively by reverse Dot Blot, Denaturant Gradient Gel Electrophoresis :
DGGE, PCR/RFLP). The (AT)xTy motifs at -540 in the silencer of beta globin gene were explored by direct sequencing.
The (AT)9 T5 configuration in the silencer of beta globin and the polymorphism C->T at -158 of gamma-G seems give explanation for Hb Bart’s carrier hémoglobinowith no identified molecular alpha-thal defects, these determinants justify
also the variable Hb Bart’s level for the same genotype carriers (α^-5nt α/αα).
Expression of Hb Bart’s at birth seems to be modulated by various factors.
The preponderant one is alpha-thal genotype. However gamma globin gene expression determinants have to be integrated in the interpretation of Hb Bart’s presence at birth especially for low levels.