Characterisation of five novel zebrafish Eph-related receptor tyrosine kinases suggests roles in patterning the neural plate.

Eph-related receptor tyrosine kinases (RTKs) are the largest known subfamily of RTKs, comprising at least a dozen members. Expression studies suggest roles for these genes in patterning and differentiation of the nervous system, the neural crest, developing limbs and somites. Some of the recently isolated family of ligands for Eph-related RTKs have been shown to function as positional identifiers in the retinotectal system. We have previously characterised three Eph-related RTKs in the zebrafish (rtk1-3). Here we report the identification of five new zebrafish Eph-related RTKs (rtk4, rtk5, rtk6, rtk7 and rtk8) and describe their dynamic expression patterns. Based on these expression patterns, we propose that rtk4-8 play various roles in establishing territories within the developing central nervous system (CNS) and in the subsequent differentiation of defined neuronal populations.