<p>Nuclear functions in eukaryotic cells are regulated by the NuA4 histone acetyltransferase complex. This is a highly-conserved protein complex that regulates multiple vital nuclear functions like the cell cycle, DNA repair and transcription. Gene expression is regulated by this complex though epigenetics by adding acetyl groups to lysine residues on histone H4. This affects the expression of genes in the regions of the chromosome where the addition occurred. The planarian flatworm Schmidtea mediterranea is thought to be, effectively, immortal due to its amazing ability to regenerate and maintain pluripotent stem cells throughout its life time. Better understanding of the genes that control differentiation and pluripotency is needed. Humans have gene homologs to the planarian counterparts; therefore, it could be possible to gain knowledge about our own stem cells from these worms. I have identified planarian homologs of 15 proteins in the human NuA4 complex (Ruvbl2, Morf4l2, Mrg15, Epc1, Tip60, Trrap, Gas41, Ruvbl1, Brd8, Yl-1, Baf53a, Dmap1, Ing3, hEaf6-1 and hEaf6-2) and silenced them by RNA interference (RNAi) to examine the role of the complex in stem cell maintenance and regeneration. The RNAi method involves feeding the worms double-stranded RNA with a sequence matching the gene of interest to target the destruction of the mRNA expressed from that gene, thus knocking down its expression. I will observe two groups of RNAi worms; a regenerating group and a homeostasis group. The regenerating will be cut following the knockdown to observe how well they restore their lost tissue. The homeostasis group will be fixed and stained to mark mitotic cells and find out if the stem cells are dividing normally. I will also use in-situ staining to determine where each of these genes are being expressed. I hypothesize that knockdown of these important regulatory complex genes will result in reduced regenerative ability and that the worms? stem cell population will not be properly maintained.