Sequence analysis and in vivo expression show that alternative splicing of ED-B and ED-A regions of the human fibronectin gene are independent events.

The structure of two alternatively spliced regions. ED-A and ED-B, of human fibronectin gene, was determined, in order to show whether any similarity was present between the two. Although some interesting features are present in each, no obvious common structure or sequence homology was found. Functional analysis of the alternative splicing events was carried out by transient expression in Hela cells. A hybrid gene was constructed by inserting the ED-B region into the third exon of the human alpha 1-globin gene. The transfected hybrid gene is expressed and produces, in Hela cells, two alternatively spliced RNAs, showing a pattern very similar to that observed for the endogenous fibronectin gene in fibroblasts. Cotransfection of this gene with a similar gene containing the ED-A region, shows that no interference is present between the two alternative splicing processes.