Investigating the Breakdown of Paternal Mitochondria with C. elegans
Authors:Ivette Alonso, Sylvia Vetrone
Mentor:Sylvia Vetrone, Assistant Professor of Biology, Whittier College
Shortly after fertilization, paternal mitochondria (p-mito) are degraded, and by the 64-cell stage of development only maternal mitochondria (m-mito) are present. The mechanism by which p-mito are degraded has not yet been clarified. In a cell, degradation can occur through autophagy or the proteasome, with both systems recognizing the target to be removed. Recent studies using the nematode model, Caenorhabditis elegans (C. elegans), have shown that the LGG-1 autophagosome protein associates with p-mito, and both disappear by the 16-cell stage. In addition, two proteins, Pink-1 and Parkin, have also been identified as key players in degradation; Pink-1 translocates to the outer mitochondrial membrane recruiting Parkin, an E3 ligase that can promote ubiquitination, while others studies have also shown Parkin’s recognition by the autophagosome. Taken together, these studies suggest a possible connection between the ubiquitin-proteasome and autophagy processes. We hypothesize that in early development of C. elegans p-mito become depolarized and tagged by Parkin, which leads to their degradation by both the autophagosome and proteasome. Therefore, in this study we investigated the role of Parkin and Pink-1 in the breakdown of p-mito in C. elegans. Briefly, HIM-5 C. elegans males were stained with Mitotracker Orange® to tag their mitochondria, and then mated with wildtype N2 C. elegans hermaphrodites to achieve standard sexual reproduction, and the fate of the stained p-mito were followed over the first 14 hrs post fertilization. Both male and hermaphrodite C. elegans were also stained for the presence of Parkin-1 and Pink proteins before mating. Our preliminary findings indicate that p-mito are indeed degraded by the 6th hour post fertilization, and that Pink and Parkin-1 associate with depolarized mitochondria in both male and hermaphroditic nematodes. Future efforts will explore if Pink and Parkin-1 are co-staining only with Mitotracker Orange® tagged p-mito and not m-mito post fertilization.