Kidney development starts with the reciprocal induction of mesenchymal and
ureteric bud nephron formation in the mesenchyme. To identify cells which l
eads to condensation, changes in gene expression during these processes, we
compared differential display polymerase chain reaction (PCR) profiles of
uninduced and induced mesenchymal cells. In vitro kidney development in the
form of the transfilter organ culture system was used to generate homogene
ous cell populations for this type of comparison. Here we describe the isol
ation of known and novel genetags from this screening. Among the known gene
s the ufo receptor tyrosine kinase, sFRP2, and the groucho related gene (gr
g) were verified as being upregulated upon induction. With four of eight no
vel genes tested, Northern blot analysis proved to be sensitive enough to c
onfirm differential expression. To improve sensitivity and gain additional
spatial information, in situ hybridization was performed. Expression analys
is of two differential display PCR products, designated CO-5 and M2-4, demo
nstrated the cell-specific and dynamic expression of these novel genetags i
n the developing kidney and other tissues. CO-5 transcripts were expressed
in the ureteric bud, S-shaped and in the collecting system. Signals For M2-
4, a gene not detectable Northern blot analysis, were only found in condens
ing mesenchymal cells and early differentiation stages, but not in the coll
ecting ducts. The large Fraction of novel genetags from the present screeni
ng that have not yet been analyzed provides a rich resource to clone generi
c networks regulating early nephrogenesis. (C) 1999 Wiley-Liss, inc.