Mapping proximal and distal splicing-regulatory elements PROJECT SUMMARY Alternative splicing (AS) of precursor mRNA is a molecular mechanism that allows single genes to generate multiple transcript and protein isoforms, providing a major driving force of molecular diversity in mammals including humans. AS is tightly regulated temporally and spatially to determine the types and level of protein products expressed in specific cellular contexts. Such regulation is dictated by numerous splicing-regulatory elements (SREs) in the alternative exon or flanking introns that are recognized by RNA-binding splicing factors. Aberrant splicing caused by disruption of SREs is implicated in an expanding list of genetic diseases ranging from neurological disorders to cancer, as well as phenotypic variation in human populations. This is reflected in recent findings that splicing quantitative trait loci (sQTLs) are as prevalent as gene expression QTLs, and they are similarly enriched in genetic variants associated with human diseases identified by GWAS. In addition, modulation of splicing or correction of dysregulated splicing has become a powerful therapeutics approach. Despite the remarkable progress of the field, identification of causal splicing-disrupting variants and therapeutic targets has been severely impeded by the lack of comprehensive SRE annotations in the human genome, as compared to similar maps of transcriptional or epigenetic regulatory elements. To fill in this tremendous gap, this study proposes an unbiased, high-throughput screening approach to map functional SREs, including those in distal regions that are largely overlooked by current studies. If successful, this platform technology will facilitate the genomic research community to study gene expression regulation, elucidate genotype-phenotype relationships, and develop RNA-based medicine.