Fig. 1.

A: mRNA expression of different FGF receptors (FGFRs) in the proximal tubule. Proximal tubules were dissected, total RNA was isolated, and the products of RT-PCR were fractionated on a 1% agarose gel. FGFR1, FGFR3, and FGFR4 but not FGFR2 mRNA are expressed in the proximal tubule. The details of the primer sequences are described in methods. Either of the FGFR3 primer sets was used. The negative control for each primer set was a RT-PCR in which RT (reverse transcriptase) was omitted. B: absence of FGFR1 transcript in the proximal tubule of FGFR1^−/− mice. Proximal tubules were dissected, total RNA was isolated, and the products of RT-PCR were fractionated on a 1% agarose gel. FGFR1 mRNA was not detected in the proximal tubules of FGFR1^−/− mice, whereas FGFR3 and FGFR4 mRNA are expressed in the proximal tubule. RT-PCR in which RT was omitted served as a negative control, and mRNA from a wild-type mouse was used as a positive control.