Molecular biologists often think of genomes as a collection of ?good? genes all providing a beneficial function for the organism. Therefore, disease is often thought of as failure of one of these ?good? genes. For example, infertility could be caused by failure of a gene that normally promotes fertility. On the other hand, an alternative source of infertility are killer meiotic drivers. Killer meiotic drivers cause infertility, not by failing to do their job, but by actively destroying the gametes that do not inherit them. These selfish parasites can therefore increase their transmission into up to 100% of the progeny of a heterozygous individual. Killer meiotic drive has been observed in a wide-range of eukaryotes from plants to mammals and has important implications for speciation, genome evolution, and the causes of infertility. We recently identified Schizosaccharomyces kambucha wtf4 as a killer meiotic driver. A single wtf4 killer allele can generate two proteins using alternate transcripts: a trans-acting poison and a gamete-specific antidote. The goal of this project is to characterize the mechanism by which wtf4 enacts poison-antidote meiotic drive. I have developed a model in which Wtf4poison oligomerizes to form a pore that interrupts a vital cellular membrane. Wtf4antidote will interact with the poison and inhibit this function or localization. To test this model, I will investigate localization and interaction of tagged Wtf4 proteins with guidance from the Stowers Institute?s fluorescence microscopy core. I will be trained in techniques such as Fluorescence resonance energy transfer (FRET) and Fluorescence correlation spectroscopy (FCS) to examine the nature, localization, and potential complexing of the Wtf4 proteins. In complement, I will work closely with the Stower?s Electron Microscopy Core to investigate how Wtf4 expression relates to cellular ultrastructures. These experiments will provide advanced training in various microscopy techniques and will either support my model or help me to develop a new one. Then, I will study poison-antidote specificity using different wtf alleles. We have previously characterized that different wtfs have different poison-antidote specificities: one Wtfantidote does not always recognize a different Wtfpoison. Antidotes can be specific to only the poison generated by the same wtf allele, or can be promiscuous and recognize multiple poisons. What determines this recognition and specificity is unknown. To assay poison- antidote specificity, I will systematically alter amino acids, gaining valuable training in evolution-guided molecular approaches. Successful completion of this work will provide insight into a mechanism of meiotic drive, guiding our understanding of the origins of infertility and genomic conflict.
A killer meiotic driver is an ultra-selfish DNA locus that can destroy gametes (e.g. sperm) that do not possess it, directly causing infertility. Killer meiotic drivers are thought to be common, but few have been cloned or mechanistically characterized. This project seeks to characterize wtf4, a killer meiotic driver found in fission yeast, as a model system for gaining a mechanistic understanding of how gamete-killers cause infertility.
