A MOLECULAR STRATEGY DESIGNED FOR THE RAPID SCREENING OF GENE TRAPS BASED ON SEQUENCE IDENTITY AND GENE-EXPRESSION PATTERN IN ADULT MICE

We have devised a strategy to rapidly screen gene traps in mouse embry onic stem (ES) cells based on DNA sequence information and an in vitro analysis of gene expression. After the initial identification of ES c ell clones expressing beta-galactosidase, tagged RNA transcripts were immediately cloned and sequenced in order to determine their identitie s. Novel gene sequences found were used to probe northern blots to exa mine the expression patterns of their cognate genes. Our initial chara cterization of 30 cDNA clones indicated that more than half of the tag ged sequences were novel mouse genes and of these 40% showed a restric ted pattern of expression in adult mouse tissues. This molecular chara cterization of gene traps is quick, reliable and well suited for the l arge-scale screening of mammalian developmental genes. Furthermore, si nce gene trap insertion frequently disrupts the tagged host gene, the ES cells can be used to produce transgenic animals for a genetic analy sis of gene function.