Alternative splicing of pre-mRNA: Developmental consequences and mechanisms of regulation

Alternative splicing of pre-mRNAs is a powerful and versatile regulatory me chanism that can effect quantitative control of gene expression and functio nal diversification of proteins. Tt contributes to major developmental deci sions and also to fine tuning of gene function. Genetic and biochemical app roaches have identified cis-acting regulatory elements and trans-acting fac tors that control alternative splicing of specific pre-mRNAs. Both approach es are contributing to an understanding of their mode of action. Some alter native splicing decisions are controlled by specific factors whose expressi on is highly restricted during development, but others may be controlled by more modest variations in the levels of general factors acting cooperative ly or antagonistically. Certain factors play active roles in both constitut ive splicing and regulation of alternative splicing. Cooperative and antago nistic effects integrated at regulatory elements are likely to be important for specificity and for finely tuned differences in cell-type-specific alt ernative splicing patterns.