cDNA of a novel mRNA expressed predominantly in mouse kidney

We examined embryonic carcinoma (EC) cells for a potential prototype molecu le of C3, the third component of complement. PCR primers, corresponding to the base sequence derived from the C3 cDNA of several species, were used fo r PCR amplification of the EC cell cDNA. All the PCR products obtained had the same sequence and showed no sequence homology to C3. Subsequently, cDNA clones were isolated from a mouse liver cDNA library using the PCR product as a probe. Unexpectedly, neither the base sequence of the cDNA clones nor the amino acid sequence deduced from the cDNA showed homology to C3, altho ugh partial homology was observed to a number of sequences from EST databas es. We designated this new clone NCU-G1. Northern hybridization experiments revealed that NCU-G1 is expressed constitutively, not only in the mouse fe tus but also in various mouse tissues, and is most abundant in the kidney c ortex.