Her 4

Her-4, more commonly called ErbB4, is a member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. Like the epidermal growth factor receptor, Her-4 is able to bind to several activating ligands and dimerize with every other member of the EGFR family. Knock-outs of Her-4 in mice show developmental defects. However, Her-4 is thought to be expressed in low quantities, if at all, in most tissues, in contrast to the other Her receptors.