FER (Fer tyrosine kinase) is a member of the FPS/FES family of nontransmembrane receptor tyrosine kinases. FER shares a functional domain and is involved in signaling pathways through receptor tyrosine kinases (RTK) and cytokine receptors. The Fes /Fps family is distinct from c-Src, c-Abl and related nRTKs and was originally distinguished as a homolog to retroviral oncoproteins. In vivo, Fer kinase assembles into homotrimers via conserved coiled-coil domains. The N-terminal coiled-coil domains of Fer can autophosphorylate in trans, thereby regulating their cellular function through differential phosphorylation states. Growth factor e, Xenopus/Amphibian,posure can induce tyrosine phosphorylation of Fer and recruitment of Fer to RTK comple, Xenopus/Amphibian,es containing p85. It is e, Xenopus/Amphibian,pressed predominantly in mature hematopoietic cells of the granulocytic and monocytic lineage, and has been shown to be e, Xenopus/Amphibian,pressed in vascular endothelial cells. Fer is implicated in insulin signaling, cell-cell signaling, human prostatic proliferative diseases, and is involved in the regulation of G1 progression.