Use of large-scale expression cloning screens in the Xenopus laevis tadpole to identify gene function

We have conducted an expression cloning screen of approximately 50,000 cDNA s from a tadpole stage Xenopus laevis cDNA library to functionally identify genes affecting a wide range of cellular and developmental processes. Fift y-seven cDNAs were isolated for their ability to alter gross tadpole morpho logy or the expression patterns of tissue-specific markers. Thirty-seven of the cDNAs have not been previously described for Xenopus, and 15 of these show little or no similarity to sequences in the NCBI database. The screen and the identified genes are presented in this paper to demonstrate the pow er, ease, speed, and flexibility of expression cloning in the X. laevis emb ryo. Future screens such as this one can be done on a larger scale and will complement the sequence-based screens and genome-sequencing projects which are producing a large body of novel genes without ascribed functions. (C) 2000 Academic Press.