School of Science Division of Life Science 35 Genetic Studies on Stem Cell Regulation Supervisor: XIE Ting / LIFS Co-supervisor: TU Renjun / LIFS Student: LIN Muyun / BCB Course: UROP1100, Fall The term ‘transposable element’ (TE) refers to the piece of DNA sequence that is capable of changing its own position within the genome by inserting it into random positions. In previous research it has been identified that piwi-interacting RNA (piRNA) acts as a master repressor in the silencing of TE, especially in Drosophila, bringing genetic stability as well as maintaining germline stem cells (GSCs). 5-methylcytosine (5mC) is an abundant RNA modification that controls many aspects of RNA metabolism, like RNA stability, splicing, nuclear export, and so on. However, it remains unknown if RNA 5mC modification regulated TE silencing. In this study, by using a TE/piRNA reporter, Burdock-GFP, we found that RNA 5mC modification is involved in TE regulation. Overexpression of a dominant-negative form of Yps (YpsW68A, has been shown to affect RNA 5mC modification in the previous study), and knockdown of RNA 5mC methyltransferases, Nsun2 and Nsun4, significantly increases Burdock-GFP expression, indicating TEs are upregulated when disrupting RNA 5mC modification. In the future study, we will focus on investigating the molecular and genetic mechanisms that how RNA 5mC modification controls TEs silencing. Genetic Studies on Stem Cell Regulation Supervisor: XIE Ting / LIFS Co-supervisor: TU Renjun / LIFS Student: ONG Gavyn Kye Wen / BCB Course: UROP1000, Summer Stem cells generate new copies of existing cell types for differentiation and replacement of old or damaged cells and produce more stem cells for infinite stem cell production of an organism. This could be investigated in Drosophila ovaries. Virgin female flies with nos-gal4 and c587-gal4 transgenes were crossed with male flies with 896 RNAi lines and one control line. The offspring were collected, taken care of and cultured for maturation. Mature female flies were dissected for its ovaries and immunostaining was performed. The ovaries were mounted and viewed under a confocal microscope. The abnormal phenotypes were captured and investigated in how these abnormalities affect stem cell regulation.