A Common Mutation in the Tyrosine Kinase Domain of the Fibroblast Growth Factor Receptor 3 Gene in Two Japanese Patients with Hypochondroplasia

We examined two Japanese patients with hypochondroplasia (HCH) whether they had mutations in the gene (FGFR3) encoding the fibroblast growth factor receptor 3 using polymerase chain reaction (PCR) coupled with direct sequencing. In both of our patients, a C→A transversion was detected in nucleotide 1659, predicting a substitution of asparagine for lysine at position 540 of the mature protein which corresponds a part of the tyrosine kinase 1 (TK1) domain. Our results suggest that a common mutation specific for HCH in the TK1 domain of FGFR3 exists among Japanese patients with HCH.