Mouse Samd9l is not a functional paralogue of the human SAMD9, the gene mutated in normophosphataemic familial tumoral calcinosis.

Normophosphataemic familial tumoral calcinosis, charac-terized by ectopic mineralization of skin, is caused by mutations in the SAMD9 gene located in human chromosome 7q21, next to a paralogous gene, SAMD9-like (SAMD9L). The mouse does not have a SAMD9 orthologue, Samd9, because it has been deleted during evolution owing to genomic rearrangements. It has been suggested that the mouse Samd9l gene serves as a functional paralogue of human SAMD9. In this study, we examined Samd9l knockout mice with respect to ectopic mineralization. We also crossed these mice with Abcc6(tm1JfK) mice, a model system to study pseudoxanthoma elasticum, to see whether the absence of the Samd9l gene modifies the mineralization process. Necropsy analysis of Samd9l(tm1Homy) mice revealed no evidence of ectopic mineralization, and deletion of the Samd9l gene in mice failed to modify the mineralization process on the Abcc6(tm1JfK) background. Collectively, the results suggest that mouse Samd9l is not a functional paralogue of human SAMD9.