Figure 1.

Expression of hFGFR3 in TG mice. (a) Schematic diagram of p1026X-hFGFR3 TG vector. The vector includes a 9.7 kb NotI fragment that contains 3.2 kb of Lck proximal promoter sequences (thick line), a 1 kb Eμ enhancer fragment (red box) inserted into these sequences, a 3.4 kb human FGFR3 cDNA (green box is coding) cloned into a BamHI site located 37 bp from the lck promoter, and a 2.1 kb human growth hormone (hGH) genomic fragment with five exons (boxes), and a polyadenylation site. FGFR3 and the fourth exon of hGH contain stop codons, as indicated by the asterisks. The spliced hFGFR3-hGH transcript is 4.4 kb. (b) Immunoblot of hFGFR3 in plasma cells. Plasma cells were generated in vitro by 5 days LPS stimulation of spleen cells from four independent F1 TG mice (founders H1, D3, A5, K1) and a non-TG littermate (WT). Proteins from total cell lysates were immunoprecipitated with a polyclonal anti-hFGFR3, fractionated by electrophoresis on a 7.5% polyacrylamide gel in SDS, transferred to nitrocellulose filters, and reacted with a monoclonal anti-hFGFR3 antibody. H929 MM cell line expresses FGFR3 as a result of a t(4;14) translocation. The FGFR3 doublet, which is present in the H929 myeloma cell line and TG splenocytes, probably reflects differential glycosylation as described for other tyrosine kinase receptors.²⁶ (c–f) Expression of hFGFR3 in spleen cells by immunohistochemistry. Sections of normal spleens from hFGFR3 TG mice and normal littermates were immunostained with anti-hFGFR3 antibody (brown) and counterstained with Meyer’s hematoxylin (Ventana) (blue); hFGFR3 TG at × 100 (c) and × 400 magnification (d); non-TG littermate at × 100 (e) and × 400 magnification (f).