Sev

The Sev (Sevenless) family of receptor tyrosine kinases is named after the Drosophila Sevenless receptor, a paradigm of cell-fate specification in which Ras-MAPK signaling from the Sevenless receptor determines the R7 photoreceptor fate in the developing fly eye, with Bride of sevenless (Boss) as transmembrane ligand. In the human kinome, this family is represented solely by ROS1, an orphan receptor kinase with homology to both Sevenless and the ALK family. This evolutionary kinship explains why ROS1 and ALK share highly related kinase domains, resulting in overlapping inhibitor sensitivity, most notably to crizotinib, entrectinib and lorlatinib in ROS1-rearranged tumors.