Differences between the levels of G? chain in the fetal hemoglobin in two types of hereditary persistence of fetal hemoglobin are linked with a variation in the DNA sequence

High Levels of Human γ-Globin Gene Expression in Adult Mice Carrying a Transgene of Deletion-Type Hereditary Persistence of Fetal Hemoglobin

“…The HPFH-1 deletion is the same size as that of HPFH-2 but is shifted in the 3Ј direction (relative to the HPFH-2 deletion) by approximately 6 kb at both breakpoints (42). Bakioglu et al (2) proposed that the difference in G ␥/ A ␥ ratios between HPFH-1 and HPFH-2 is due to the presence, in the HPFH-1 G ␥-gene promoter, of the Ϫ158C3T base change that is associated with preferential overexpression of the G ␥ gene over the A ␥ gene (22) and therefore would result in a G ␥/ A ␥ ratio different from that in HPFH-2, the G ␥-gene promoter of which does not contain the base change. The ␥-globin transgene used in our studies does not contain the G ␥ Ϫ158C3T change.…”

Fetal haemoglobin levels and haematological characteristics of compound heterozygotes for haemoglobin S and deletional hereditary persistence of fetal haemoglobin

“…The two most common types of deletional HPFH in people of African descent (types 1 and 2) are characterized by >80 kb deletions (Fig 1) involving HBD (d-globin gene) and HBB that are staggered by approximately 5 kb at the 5¢ and 3¢ ends (Forget, 1998). Heterozygotes for HPFH 1 and 2 have similar HbF levels (20-28%) and mean corpuscular volume (MCV) but differ in the ratio of Gc to Ac chains (approximately 50:50 in type 1 and 30:70 in type 2) (Kutlar et al, 1984;Bakioglu et al, 1986). Homozygotes for HPFH type 1 and 2 are clinically unaffected and have 100% HbF and mild microcytosis.…”

“…Heterozygotes for HPFH 1 and 2 have similar HbF levels (20-28%) and mean corpuscular volume (MCV) but differ in the ratio of Gc to Ac chains (approximately 50:50 in type 1 and 30:70 in type 2) (Kutlar et al, 1984;Bakioglu et al, 1986). Homozygotes for HPFH type 1 and 2 are clinically unaffected and have 100% HbF and mild microcytosis.…”