Alternative splicing use ratio is not conserved between human and mouse immune cells
Most human genes have mouse orthologs. However, orthology at the level of exons and alternative splicing events is not well defined, and the use of alternative splicing events in immune cell types has not been compared between human and mouse. We mapped exons and alternative splicing events between human and mouse. Based on this mapping, the use ratio of orthologous alternative splicing events was compared between human and mouse immune cell types and fibroblasts. Out of the 1,823 human-mouse orthologous alternative splicing events that are expressed in the five tested immune cell types, most (62-67%) showed a significant difference in use ratio between human and mouse, and less than third (21-25%) retained the same ratio. Our results reveal both conserved and divergent alternative splicing usage ratio, and highlight the dynamic evolution of alternative splicing regulation across human and mouse immune cell types. By integrating exon orthology with observed splicing patterns, our analysis provides a functional framework for studying mammalian splicing ratio evolution beyond static transcript annotations.