IDENTIFICATION OF ALTERNATIVELY SPLICED MESSENGER-RNAS ENCODING VARIANTS OF MDK1, A NOVEL RECEPTOR TYROSINE KINASE EXPRESSED IN THE MURINE NERVOUS

A novel member of the eck/eph family of receptor tyrosine kinases (RTK s), termed mouse developmental kinase 1 (MDK1), was identified and sho wn to be closely related to the Eek, Ehk1/Cek7, Ehk2, Cek4/Mek4/hek an d Sek/Cek8 subfamily. Northern blot analysis revealed MDK1 mRNA transc ripts of 6.8, 5.7, 4.0, 3.2 and 2.6 kb that encode apparent splice var iants. Sequence analyses of MDK1 cDNA clones from adult mouse brain pr edict the existence of at least five isoforms, including two truncated receptor variants lacking the kinase domain. Northern blot and in sit u hybridization analysis indicate that in the adult mouse MDK1 RNA exp ression is restricted to brain, testes and spleen. The distinct patter ns of MDK1 gene expression during mouse development suggest an importa nt role in the formation of neuronal structures and possibly other mor phogenic processes.