Isolation of the Complementary DNA Encoding a Mouse Heparin-binding Growth Factor Receptor with the Use of a Unique Kinase Insert Sequence

With the use of reverse transcriptase-polymerase chain reaction techniques focused on a unique kinase insert sequence, the complementary DNA for a mouse tyrosine kinase receptor gene, designated sam3> was isolated from a mouse brain complementary DNA library as a member of the heparin-binding growth factor receptor family or fibroblast growth factor receptor family. The kinase insert region was selected as the probe synthesized by polymerase chain reaction techniques because it composes a unique structure in this receptor family. The sam3 protein, 800 amino acids long, has high homology to mouse K-sam/bek (67%) and N-sam/flg (63%), which we also cloned as the mouse counterparts of human K-sam/ bek and N-sam/flg genes, other members of this family. The sam3 protein also has high homology to human FGFR3 (92%) and chicken cek2 (80%) proteins. The sam3 protein is most likely to be a mouse counterpart of human FGFR3 and chicken cek2 proteins. mRNAs of K-samlbek, N-sam/ flg, and sam3/FGFR3 genes were detected in mouse embryo through some adult tissues. The relative amounts of these mRNAs were different depending on the organs examined. Thus, these gene products may have different biological functions in organ development including the central nervous system.