Abstract Summary: Mutually exclusive splicing is a strictly regulated pattern of alternative splicing. A specific group of mutually exclusive splicing events has been shown to be regulated by the formation of specific RNA secondary structures. This type of regulation has been shown to exist only in arthropods. The present study involved a detailed sequence analysis of human gene structures that undergo mutually exclusive splicing, which showed that this type of regulation may also occur in dynamin 1 in mammals. A phylogenetic analysis revealed that the dynamin 1 orthologs in invertebrates did not share the same sequence features, which suggests that the regulatory mechanism has independently evolved in the mammalian lineage. Therefore, the emergence of this elaborate mechanism for mutually exclusive splicing may be attributable to mechanistic convergence. Contact: mikita@bioreg.kyushu-u.ac.jp Supplementary information: Supplementary data are available at Bioinformatics online.