Isolation of a gene encoding a novel receptor tyrosine kinase from differentiated embryonic stem cells.

A mouse gene encoding a receptor tyrosine kinase, designated Embryonic receptor kinase (EmRK2), was isolated from embryoid bodies (EBs) generated by differentiating embryonic stem (ES) cells in culture for 6 days. Sequence analysis of EmRK2 cDNA clones predicts a receptor with a 755 amino acid extracellular region with seven immunoglobulin-like domains, a transmembrane region, and a 552 amino acid cytoplasmic region containing the kinase domain. The kinase domain is interrupted by a stretch of hydrophilic amino acids, the kinase insert. EmRK2 is expressed in embryoid bodies, in whole embryos at day 10 and 12 of gestation, and in the embryonic yolk sac and the fetal liver. On the basis of sequence homology, EmRK2 is likely to be the mouse homologue of human flt, a receptor for vascular endothelial growth factor, and as such, could encode an endothelial cell specific receptor tyrosine kinase.