Affiliations: 1) Kansas State University; 2) University of North Dakota; 3) Presidency University, Kolkata, India
Keywords: p. cell migration; n. networks
Collective cell migration underlies many processes essential to the life of an organism, including sculpting organs during development, wound healing in the adult, and cancer metastasis. Drosophila border cells, which undergo collective cell migration during normal development, are a genetically tractable model in which to study molecular drivers of collective cell migration. In the ovary, a group of 6-10 follicle cells are specified as border cells. At mid-oogenesis, border cells round up as a cluster, detach from the underlying epithelium and begin their migration. The cluster first extends directed actin-rich protrusions to help them move rapidly through the surrounding tissue. Later, as migration slows down, the cluster rotates several times, then stops at the oocyte border. Successful border cell migration relies on cell signaling, polarization of the cluster, including directed protrusions, remodeling of the actin cytoskeleton, and maintenance of adhesion between border cells and with the nurse cell migratory substrate. Signals from ecdysone, JAK/STAT, EGFR/PVR, and other pathways initiate and direct the migration of border cells. Downstream targets of these signaling pathways, however, are poorly characterized. Nor is it known which genes, if any, are differentially expressed during distinct migration stages. Thus we wanted to identify genes whose expression changed during border cell migration. We performed RNA-sequencing on border cells specifically isolated at pre-, mid-, and late-migration stages. Transcriptome analyses of these cells showed that 1,794 transcripts (1,394 unique genes) were significantly differentially expressed during border cell migration. Downstream analyses, including clustering of genes by expression patterns and testing for gene ontology enrichment and genetic networks, identified nine groups of differentially expressed genes. Many of these genes have known roles in cell junction assembly, epithelial differentiation, cellular morphogenesis, the actin cytoskeleton, and epithelial-to-mesenchymal transitions, but also metabolic processes. To validate this RNA-sequencing approach, we confirmed the expression and/or function of a subset of these genes in border cells, including CG11147, CHES-1-like, and Arf51F. Thus, our transcriptome analysis identified differentially expressed genes in migrating border cells and highlighted multiple genetic networks, as well as individual genes, that may function in border cell migration.