10 - Elucidating the mechanism of purifying selection using C. elegans
University of California, Santa Barbara
Molecular, Cellular and Developmental Biology
Purifying selection, the process of eliminating mutant mitochondrial DNA (mtDNA) molecules from cells during egg and embryo development is not well understood. Yet, because mitochondria produce more than 90% of our cellular energy, mtDNA plays a fundamental role in energy metabolism, growth and aging. This project explores the dynamics of mtDNA removal during cell death in the development of the egg and during mitochondrial segregation in the developing embryo, using the nematode C. elegans. To identify genes involved in purifying selection, I have conducted genetic crosses to produce strains with mitochondrial and nuclear DNA mutations. I have confirmed the crosses by visualizing for fluorescence and measuring DNA fragment length, accounting for the maternal inheritance of mitochondrial genes. Using these strains, we can identify genes involved in purifying selection by determining the rate of mtDNA mutation removal compared against a baseline rate. Additionally, to study early embryonic purifying selection mechanisms, I am constructing a strain that expresses fluorescent mitochondria in the early embryo using Gateway cloning, which will allow us to visualize mitochondrial movement in the embryo. We predict that healthy mitochondria segregate preferentially to the posterior axis of a developing embryo, as this differentiates into the germline and gives rise to egg cells that can pass on their DNA in inheritance. Preliminary results have confirmed the cloned vectors indicating successful integration of desired DNA sequences. These results show promise towards better understanding and treatment of the debilitating neuromuscular mitochondrial myopathies that affect 4000 children in the US each year.