Maternal inheritance of mitochondrial DNA (mtDNA) is highly conserved in metazoans. While many species eliminate paternal mtDNA during late sperm development to foster maternal inheritance, the regulatory mechanisms governing this process remain elusive. Through a forward genetic screen in Drosophila, we identified 47 mutant lines exhibiting substantial retention of mtDNA in mature sperm. We mapped one line to poldip2, a gene predominantly expressed in the testis. Disruption of poldip2 led to substantial mtDNA retention in mature sperm and subsequent paternal transmission to progeny. Further investigation via imaging, biochemical analyses and ChIP assays revealed that Poldip2 is a mitochondrial matrix protein capable of binding mtDNA. Moreover, we showed that ClpX, the key component of a major mitochondrial protease, interacts with Poldip2 to co-regulate mtDNA elimination in Drosophila spermatids. This study sheds light on the mechanisms underlying mtDNA removal during spermatogenesis and underscores the pivotal role of this process in safeguarding maternal inheritance.
Wang et al. (Tue,) studied this question.