Ephrin B1

Ephrin B1, also known as EFNB1, is a member of the ephrin family of receptor ligands. Ephrins are a large family of transmembrane proteins that play crucial roles in a variety of developmental processes, including axon guidance, cell migration, and tissue boundary formation. They interact with Eph receptor tyrosine kinases.

Ephrin B1 is a type B ephrin, characterized by its transmembrane domain. Unlike type A ephrins, which are typically linked to the cell membrane via a glycosylphosphatidylinositol (GPI) anchor, type B ephrins contain a transmembrane region and a cytoplasmic domain. This cytoplasmic domain allows for bidirectional signaling; that is, signaling can occur not only in the Eph receptor-expressing cell (forward signaling) but also in the ephrin-expressing cell (reverse signaling).

Specifically, Ephrin B1 interacts with EphB receptors. The interaction between Ephrin B1 and EphB receptors triggers receptor activation and downstream signaling cascades, which can influence cell adhesion, cytoskeletal reorganization, and gene expression.

Ephrin B1 has been implicated in several developmental processes, including hindbrain segmentation, angiogenesis, and skeletal development. Mutations in the EFNB1 gene in humans have been associated with craniofrontonasal syndrome (CFNS), a developmental disorder characterized by specific facial and skeletal abnormalities. The X-linked inheritance pattern of CFNS is linked to the EFNB1 gene being located on the X chromosome. The unusual manifestation of CFNS, with more severe phenotypes in heterozygous females than hemizygous males, is thought to be related to cellular interference caused by X-chromosome inactivation mosaicism. The role of Ephrin B1 in CFNS highlights its importance in proper craniofacial development.