Expression of truncated Sek-1 receptor tyrosine kinase disrupts the segmental restriction of gene expression in the Xenopus and zebrafish hindbrain.

During development of the vertebrate hindbrain regulatory gene expression is confined to precise segmental domains. Studies of cell lineage and gene expression suggest that establishment of these domains may involve a dynamic regulation of cell identity and restriction of cell movement between segments. We have taken a dominant negative approach to interfere with the function of Sek-1, a member of the Eph-related receptor tyrosine kinase family expressed in rhombomeres r3 and r5. In Xenopus and zebrafish embryos expressing truncated Sek-1, lacking kinase sequences, expression of r3/r5 markers occurs in adjacent even-numbered rhombomeres, in domains contiguous with r3 or r5. This disruption is rescued by full-length Sek-1, indicating a requirement for the kinase domain in the segmental restriction of gene expression. These data suggest that Sek-1, perhaps with other Eph-related receptors, is required for interactions that regulate the segmental identity or movement of cells.