We report the isolation of the mouse Ovca1 gene, the orthologue of human OVCA1/DPH2L1, a putative tumor suppressor associated with ovarian cancer. Mouse Ovca1 contains at least 13 exons and spans approximately 17 kb. Northern analysis showed that Ovca1 is expressed in most adult mouse tissues. The most predominant Ovca1 transcript is 2.1 kb. RT-PCR analysis demonstrated Ovca1 expression in embryos from 8.5 days postcoitum (d.p.c.) to 10.5 d.p.c., and various organs of 14.5 d.p.c. embryos. Mouse Ovca1 encodes a protein of 438 amino acids and has high identity with human OVCA1. Western blot and immunohistochemistry revealed that mouse OVCA1 is a 50-kDa protein that is predominately localized in a punctate pattern in the nucleus. Based on gene homology, structure, and expression patterns, these findings indicate that mouse Ovca1 is the orthologue of human OVCA1/DPH2L1. This study will facilitate experiments to elucidate the in vivo role of Ovca1 in cancer.