HBB

Hbb is most commonly an abbreviation for the hemoglobin subunit beta gene (HBB) in humans. The gene encodes the beta chain of adult hemoglobin (HbA), a tetramer consisting of two alpha and two beta chains. The beta-globin protein is 147 amino acids long and is expressed primarily in erythroid cells during red blood cell development. The HBB gene is located on chromosome 11 and is part of the beta-globin gene cluster, which also includes HBD (delta-globin), HBG1 and HBG2 (gamma-globin), and HBE1 (epsilon-globin). The alpha-globin genes (HBA1 and HBA2) belong to a separate cluster on chromosome 16. Expression is regulated by elements such as the locus control region (LCR), ensuring proper temporal and quantitative expression during erythropoiesis.

Mutations in HBB cause several inherited blood disorders. The most common are beta-thalassemias, resulting from mutations that reduce or abolish beta-globin production. Sickle cell disease arises from a single point mutation (Glu6Val) in HbS, leading to polymerization of deoxygenated hemoglobin and red blood cell sickling. Clinical severity ranges from asymptomatic trait to severe anemia, depending on zygosity and coexisting genetic factors. Treatments include supportive care, transfusions, and therapies that induce fetal hemoglobin (HbF), which can ameliorate disease in some cases.

Beyond medicine, HBB is a widely used symbol in genetics and genomics to denote the gene and its protein product. The lowercase spelling hbb is uncommon in contemporary biomedical literature, where HBB is the standard reference. The term may appear in some databases or naming conventions, but HBB consistently refers to the beta-globin gene and its protein.