The nuclear genes Mtfr1 and Dufd1 regulate mitochondrial dynamic and cellular respiration.

Dufd1 (DUF729 domain containing 1) is related to Mtfr1 (mitochondrial fission regulator 1), a gene involved in the regulation of antioxidant activity in the mouse testis. The present study was undertaken to better understand their role in regulating mitochondrial architecture and function in the mouse. We show that Dufd1 is expressed as a 2 kb mRNA and has a more specific tissue pattern compared to Mtfr1, with highest level of expression in testes, lower level in spleen, and negligible levels in other organs and/or tissues. In the male gonad, Dufd1 mRNA expression increases during postnatal development, similarly to Mtfr1. In situ hybridization and real-time PCR analyses show that Dufd1 is expressed in the seminiferous tubules by middle-late pachytene spermatocytes and spermatids. In transfected cells, the Dufd1-tagged protein is located in mitochondria, associated with the tips of mitochondrial tubules and to tubules constrictions, and induces mitochondrial fission although with a lesser efficiency than Mtfr1. We also found that both endogenous Dufd1 and Mtfr1 proteins are associated with membrane-enriched subcellular fractions, including mitochondria. Inhibition of Mtfr1 and/or Dufd1 expression, in a testicular germ cells line, severely impairs O(2) consumption and indicates that both genes are required for mitochondrial respiration. Accordingly, analysis of testes mitochondria from Mtfr1-deficient mice reveals severely reduced O(2) consumption and ATP synthesis compared to wt animals. These data show that, in murine testis, Dufd1 and Mtfr1 have redundant functions related to mitochondrial physiology and represent genes with a potential role in testicular function.