Our findings demonstrate that alternative splicing of exon 16 is an important feature of ovarian cancer, that this is associated with poor patient outcomes, and that alternative splicing of exon 16 results in the expression of DNM1L/Drp1 proteins with distinct roles related to the regulation of mitochondrial form and function, which impacts pro-tumorigenic behavior in culture and in vivo. The gene discussed is DNM1L; the disease is ovarian carcinoma.