Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 76

Tabl e 3. 4. -globin

locus consist of the transiently expressed (the first 12 weeks after conception) embryonic gene
HBZ followed by HBM, HBA2, HBA1, and HBQ1 genes (from 5 to 3 end). The HBQ1 gene is
expressed very early in embryos erythroid cells, but not in adult erythroid or other non-erythroid
cells. The

Human hemoglobin (HB) genes and its products (Hb). The genes in the α

θ -globin family consists of the HBQ1 gene that encodes θ 1-globin and at least a

truncated, processed ψθ 2 pseudogene located on chromosome 22, whereas HBZP ( ψζ 1) and

HBAP2 ( ψα 2) pseudogenes localize downstream from the HBZ ( ζ 2) gene, and HBAP1 ( ψα 1)

pseudogene downstream from the HBM gene. The genes in the -globin locus are also arranged

sequentially (HBE1, HBG2, HBG1, HBD, and HBB from 5 to 3 end), beginning with the gene
expressed during embryogenesis and ending with the gene expressed in adults. The 2 HBG genes
that produce hemoglobin-F are active during fetogenesis.

β

Gene Protein

α -Globin locus on chromosome 16

HBZ Hemoglobin- ζ , ζ -globin

HBM Hemoglobin- , -globin

HBA2 Hemoglobin- α 2, α 2-globin, HbH

HBA1 Hemoglobin- α 1, α 1-globin, CD31, HbH

HBQ1 Hemoglobin- θ 1, θ 1-globin

β -Globin locus on chromosome 11

HBE1 Hemoglobin- , -globin

HBG2 Hemoglobin- γ 2(G), γ 2-globin, G γ -globin (Paulinia)

methemoglobin

HBG1 Hemoglobin- γ 1(A), γ 2-globin, A γ -globin

HBD Hemoglobin- δ , δ -globin

HBB Hemoglobin- β , β -globin

Tabl e 3. 5. Functional and dysfunctional types of hemoglobins (FHQTL: fetal hemoglobin QTL
on chromosome 8).

Category Types Tetramer composition

Developmental stages

Embryo Gower 1 ζ

2 2

Gower 2 α 2 2

Portland ζ 2 γ 2

Fetus Hemoglobin-F α γ 2 2

( ≥ week 9) FHQTL

Adult Hemoglobin-A (A1) α 2 β 2

Hemoglobin-A2 α 2 δ 2

Variants responsible for hemoglobinopathies

2

Hemolytic anemia Hemoglobin-C α δ 2

2

Hemolytic anemia Hemoglobin-E α δ 2

α Thalassemia Hemoglobin-H β

4

α Thalassemia Hemoglobin Barts γ 4

2

Sickle cell disease Hemoglobin-S α 2 δ