View Program - 63rd Annual Drosophila Research Conference

Uniparental inheritance of mitochondria is one of the most conserved phenomena across evolution, occurring in diverse species, ranging from fungi and plants to mammals. In almost all animals, the sperm enters the egg with its mitochondria, resulting in a short period where mitochondria from both parents reside within the forming zygote. However, rapidly after fertilization, sperm mitochondria are eliminated, leaving the zygote solely with maternal mitochondria, which will further propagate in the developing embryo. Why and how paternal mitochondria are eliminated remain a matter of speculation and controversy, respectively. It is believed that massive heteroplasmy (i.e. the presence of more than one mitochondrial (mt)DNA type in a cell) is deleterious to the organism, but the overwhelming number of egg mitochondria (up to 600,000 in human) as compared with sperm mitochondria (50-75 in human) could not lead to massive heteroplasmy. Furthermore, in some organisms, such as Drosophila, sperm mtDNA is eliminated already during spermatogenesis, yet sperm vacuolar mitochondria are still targeted for destruction after fertilization. Whether the mechanism of paternal mitochondria elimination is conserved across species is unclear. Some studies suggest a passive mechanism whereby paternal mitochondria are diluted beyond detection by the overwhelming number of maternal mitochondria. On the other hand, other studies, including in Drosophila, suggest an active egg-derived paternal mitochondrial destruction mechanism.
Here, I will present our recent unpublished discovery of a non-canonical cell intruder targeting system, consisting of combined elements from the endocytic, phagocytic, and autophagic systems, which specifically targets sperm mitochondria for destruction after fertilization in Drosophila. These elements are conserved between Drosophila and human, implying that similar mechanisms might also operate to eliminate paternal mitochondria, at least in all flagellated sperm organisms.

Cell intruder targeting system mediates paternal mitochondrial destruction after fertilization in Drosophila