SEVERAL RECEPTOR TYROSINE KINASE GENES OF THE EPH FAMILY ARE SEGMENTALLY EXPRESSED IN THE DEVELOPING HINDBRAIN

Pattern formation in the hindbrain involves a segmentation process lea ding to the formation of metameric units, manifested as successive swe llings known as rhombomeres (r). In search for genes involved in cell- cell interactions during hindbrain segmentation, we have screened for protein kinase genes with restricted expression patterns in this regio n of the CNS. We present the cloning of three novel mouse genes, Sek-2 , Sek-3 and Sek-4 (members of the Eph subfamily of putative transmembr ane receptor protein tyrosine kinases (RTKs)), the identification of t heir chromosomal locations, and the analysis of their expression betwe en 7.5 and 10.5 days of development. Before morphological segmentation , Sek-2 is transcribed in a transverse stripe corresponding to prospec tive r4 and the adjacent mesoderm, suggesting possible roles both in h indbrain segmentation and signalling between neuroepithelium and mesod erm. Sek-3 and Sek-4 have common domains of expression, including r3, r5 and part of the midbrain, as well as specific domains in the dience phalon, telencephalon, spinal cord and in mesodermal and neural crest derivatives. Together with our previous finding that Sek (Sek-1) is ex pressed in r3 and r5 (Gilardi-Hebenstreit et al., 1992; Nieto et al., 1992), these data indicate that members of the Eph family of RTKs may co-operate in the segmental patterning of the hindbrain.