Together with Abl, involved in embryonic axonal development. Not detected in pregastrula embryos. Upon gastrulation, detected in the epidermis and visceral mesoderm. The expression pattern undergoes a pronounced change, such that epidermal expression decreases to background levels while mesodermal expression remains high. Visceral mesoderm expression decreases once formation of the gut tube is complete. Concurrently, central nervous system expression intensifies. Also detected in the peripheral nervous system. Belongs to the FAX family.