HBE1

HBE1, short for hemoglobin subunit epsilon 1, is a protein-coding gene in humans that encodes the epsilon-globin chain. The epsilon chain is a component of embryonic hemoglobins, most notably forming heterotetramers with alpha globin during early development. In the embryo, these embryonic hemoglobins facilitate oxygen transport before the fetal and adult hemoglobins become predominant.

Genomic context and expression pattern

HBE1 is part of the beta-like globin gene cluster, located on chromosome 11, and is regulated as part of a coordinated system that controls globin gene expression across development. Epsilon-globin expression is tightly developmentally regulated: it is expressed in primitive erythroid cells of the yolk sac during early gestation and is largely silenced as fetal development progresses, with adult erythrocytes containing little to no epsilon-globin.

Protein products and role in development

The protein product of HBE1 pairs with alpha-globin to form embryonic hemoglobins, such as Hb epsilon-containing tetramers. These embryonic forms are gradually replaced by fetal and then adult hemoglobins as development proceeds, reflecting changes in oxygen transport needs and regulatory controls within erythroid cells.

Regulation and clinical relevance

HBE1 expression is governed by stage-specific transcription factors and regulatory elements within the globin gene clusters, including locus control region–driven regulation. Rare genetic variations affecting HBE1 can impact embryonic hemoglobin composition, a situation described in the broader context of globin gene disorders; such changes are typically of limited clinical consequence after birth due to silencing of epsilon-globin in adulthood.

Overall, HBE1 provides the epsilon-globin component of embryonic hemoglobins and is primarily active during early development, with expression diminishing before or shortly after birth.