CLONING OF MULTIPLE CHICKEN FGF1 MESSENGER-RNAS AND THEIR DIFFERENTIAL EXPRESSION DURING DEVELOPMENT OF WHOLE-EMBRYO AND OF THE LENS

Five different 5' untranslated regions (5' UTRs) of FGF1 mRNAs mere cl oned in chicken, The structure of these transcripts suggests that, as in mammals, distinct 5' untranslated exons are spliced to the first co ding exon via alternative splicing and alternative promoter usage, In an attempt to correlate the expression of specific transcripts to dist inct biological activities, the distribution of these transcripts in d ifferent tissues and during the development of both the whole embryo a nd the lens was studied, In tissues, we have shown a differential, but not exclusive, expression of these transcripts, In the whole embryo, the expression of one transcript correlates with later developmental p rocesses, In the lens, only two transcripts were detected that are bot h differently expressed and distributed, These results suggest that th e biological properties of FGF1 depend on the expression of specific F GF1 mRNAs, Because these transcripts only differ in their 5' UTRs, the y could be involved in distinct translational controls.