A COMPILATION OF PARTIAL SEQUENCES OF RANDOMLY SELECTED CDNA CLONES FROM THE RAT INCISOR

The formation of tooth organs is regulated by a series of developmenta l programs. We have initiated a genome project with the ultimate goal of identifying novel genes important for tooth development. As an init ial approach, we constructed a unidirectional cDNA library from the no n-calcified portion of incisors of 3- to 4-week-old rats, sequenced cD NA clones, and classified their sequences by homology search through t he GenBank data base and the PIR protein data base. Here, we report pa rtial DNA sequences obtained by automated DNA sequencing on 400 cDNA c lones randomly selected from the library. Of the sequences determined, 51% represented sequences of new genes that were not related to any p reviously reported gene. Twenty-six percent of the clones strongly mat ched genes and proteins in the data bases, including amelogenin, alpha 1(I) and alpha 2(I) collagen chains, osteonectin, and decorin. Nine p ercent of clones revealed partial sequence homology to known genes suc h as transcription factors and cell surface receptors. A significant n umber of the previously identified genes were expressed redundantly an d were found to encode extracellular matrix proteins. Identification a nd cataloging of cDNA clones in these tissues are the first step towar d identification of markers expressed in a tissue- or stage-specific m anner, as well as the genetic linkage study of tooth anomalies. Furthe r characterization of the clones described in this paper should lead t o the discovery of novel genes important for tooth development.