Emily Fox and Adam Hefel present their research on 6/26/17
Prostaglandins regulate collective cell migration in the Drosophila ovary
Emily Toombs, Tina Tootle PhD, Anatomy and Cell Biology Department University of Iowa
Collective cell migration – the coordinated movement of tightly or loosely associated cells – is important for both normal development and tumor invasion. While prostaglandins (PGs), short-range lipid signaling molecules, are known to be important for single cell migration, their mechanism of action is poorly understood. One potential mechanism is via regulation of mechanotransduction. Mechanotransduction, or the transfer of physical force into electrical/chemical signals, is essential to proper cellular migration. Mechanotransduction is mediated by the direct connection of the cytoskeleton to the nucleoskeleton via the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. Our lab has shown that PGs control actin remodeling via multiple mechanisms, including via regulating Fascin. Fascin is an actin binding protein essential to cell migration and known to interact directly with the LINC complex. Despite this, PG signaling has not been previously implicated in mechanotransduction. Here we present the first evidence that PGs may regulate invasive collective cell migration and propose that this is via regulation of the LINC Complex. We assess this using a collective, invasive, epithelial migration during Drosophila oogenesis. In Drosophila, the ovary contains chains of developing follicles composed of 15 germline derived nurse cells, 1 oocyte, and a surrounding layer of somatic epithelial cells. Within these follicles, a cluster of 6-8 somatic cells delaminate from the outer epithelium and migrate invasively between the nurse cells to the oocyte border. We hypothesize that PG signaling modulates border cell migration by regulating perinuclear Fascin localization to control LINC complex function. Here we show that loss of PGs results in delayed border cell migration, as does loss of LINC complex components. Current efforts focus on determining cell specific roles of PGs in this migration. This research is expected to provide the mechanistic insight into how PGs regulate 3D cellular migration. These findings will improve our understanding of the functions of PGs, Fascin, and the LINC complex, both developmentally and during tumor progression.
“Exploring Meiotic DNA double-strand break repair in Caenohabditis elegans”
Adam Hefel, Sarit Smolikove, PhD, Biology Department University of Iowa
DNA double-strand breaks (DSBs) are a major source of genome instability, with the potential to cause mutations which can lead to cancer development. In meiosis, DSBs are programmed to form in order to produce crossovers that will promote proper chromosome segregation. Programmed DSBs are produced by the topoisomerase-like Spo-11, which requires the MRN (MRE11, RAD50, and Nbs1) complex. MRN is needed to both create DSBs and to resect the broken ends, producing single-stranded DNA to facilitate homologous recombination. Our lab has discovered a separation of function allele for mre-11 (mre-1(iow1)) in which DSBs are created but ends are not resected resulting in repair by non-homologous end-joining (NHEJ). When NHEJ is ablated in this strain, these breaks are then repaired by an unknown mechanism which results in the formation of crossovers. Using RNA-seq and inducing DSBs with gamma irradiation we expect to find differentially expressed genes representing DSB repair genes in wild-type and mre-1(iow1) mutant lines that will provide insight into this unknown repair mechanism. In order to determine the pattern of repair in this mutant, we will also generate a strain that expresses a heat-shock promoter driven Isce-I endonuclease, the 24 base-pair recognition sequence of which is not found in the C. elegans genome. By creating an engineered locus with the Isce-I cut-site and inducing expression of Isce-I in the germline, we aim to create a system that can be used to address the patterns of repair in our mre-11(iow1) mutant as well as other mutants of DNA damage repair.