A minigene contains a genomic fragment including the alternative exon(s) and the surrounding introns as well as the flanking constitutively spliced cloned in a eukaryotic expression vector.
Thus, the transfected minigenes should contain all RNA-elements necessary to show the same alternative splicing pattern as the corresponding endogenous alternatively spliced gene when compared in a specific cellular environment.

Oliver Stoss, Peter Stoilov, Annette M. Hartmann, Oliver Nayler, Stefan Stamm; Brain Research Protocols, 1999

The exact mechanisms leading to alternative splice site selection are still poorly understood. However, recently cotransfection studies in eukaryotic cells were successfully used to decipher contributions of RNA elements (cis-factors), their interacting protein components (trans-factors) or the cell type on alternative pre-mRNA splicing. Splice factors often work in a concentration dependent manner, resulting in a gradual change of alternative splicing patterns of a minigene when the amount of a trans-acting protein is increased by cotransfections.

The use of RNA-binding molecules as antibiotics, such as gentamicin, chloramphenicol, and tetracycline illustrates that drugs can be targeted against RNA and/or RNA binding proteins. High-throughput screens and testing of substances in model systems identified more substances that change splice site selection. The substances fall into several categories, including HDAC inhibitors, kinase and phosphatase inhibitors, as well as cAMP antagonist and agonists. The currently known substances are reviewed in (Sumanasekera et al., 2008 (Biochem Soc Trans. 2008)) and listed here.

The Alternative Splicing Database (ASD) Project aims to understand the mechanism of alternative splicing on a genome-wide scale by creating a database of alternative splice events and the resultant isoform splice patterns of genes from human, and other model species.