Genetic and Molecular Dissection of Meiotic Silencing by Unpaired DNA

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The goal of this project is to determine the underlying mechanism for how an unpaired DNA is silenced during meiosis, a process that produces gametes or spores. The presence of unpaired genes during this part of the cell cycle is often indicative of a foreign DNA element. Accordingly, the cell usually benefits by silencing (turning off) the expression of these genes. This pathway is called 'Meiotic Silencing by Unpaired DNA (MSUD)' and is a unique RNA-based gene silencing system first described in the orange bread mold, Neurospora crassa. But since DNA segments lacking a pairing partner are also targeted for silencing in worms, mice, and humans, the study of MSUD will shed light on how chromosome pairing affects gene regulation in higher organisms as well. To broaden the participation of underrepresented groups, the investigators of this project will recruit and train undergraduate students from their own university as well as from non-Ph.D.-granting and minority-serving institutions. Research activities from this project will be used to develop lesson plans for various outreach programs. Efforts will also be made to promote interdisciplinary partnerships and STEM (science, technology, engineering, and mathematics) education. In various organisms, genome surveillance systems are maintained to control the expression of repetitive elements and limit their spreading. One of these mechanisms is MSUD, which examines the pairing of any DNA segment with its homologous partner during meiotic prophase I. A gene not paired with a similar sequence generates a silencing signal (a small RNA species), which subsequently turns off the expression from this unpaired DNA as well as from any other (paired or unpaired) copies in the genome. MSUD utilizes common RNA interference (RNAi) factors (e.g., Argonaute) to target specific mRNA transcripts. Using the tools they have developed (e.g., protein interaction assays, mutant strains, RNA profiles, and cellular markers) and various complementary approaches (e.g., biochemistry, cytology, genetics, and molecular biology), the investigators plan to characterize Neurospora mutants defective in MSUD and examine how proteins from various sites of MSUD activity contribute to the silencing pathway.