Browsing by Subject "netrin"

Cell invasion is a complicated process vital to tissue development, immune surveillance, and disease states such as metastatic cancer. While in vitro work has presented molecular mechanisms regulating cell invasion, visualization of the process in in vivo settings provides a deeper understanding of the cell biological events of invasion. To invade, a cell must cross dense barriers of extracellular matrix and basement membrane (BM); how an invasive cell regulates its plasma membrane to facilitate breach and removal of these barriers is a poorly-understood and underconsidered question. The developmental event of C. elegans anchor cell (AC) invasion provides an in vivo model for the visualization of cell invasion. The AC, a specialized uterine cell, creates a gap in the BM separating the uterine and vulval tissues and then expands that gap through the formation of an invasive protrusion. Using live-cell imaging, RNAi screening, genome editing, and photobleaching techniques I examined the mechanisms governing plasma membrane regulation during AC invasion. In Chapter 2, I discover that the AC rapidly expands an invasive protrusion to clear underlying BM through exocytosis of lysosomes in a netrin-dependent manner. In Chapter 3, I identify a barrier to membrane diffusion formed by the BM receptor dystroglycan as being necessary for expansion of the invasive protrusion and maintenance of polarity. Chapter 4 discusses the implications of these findings and future directions.

Basement membranes are dense, sheet-like forms of extracellular matrix that

surround the epithelial tissues of metazoan organisms. While these structures are

critical for epithelial support and tissue organization, basement membranes also pose

formidable barriers to most cells. However, certain specialized cells are able to breach

these barriers and move between tissues. Acquisition of cell invasive behavior by some

tumor cells is thought be an important step in cancer progression. Due to the clear basic

and clinical importance of understanding the mechanisms underlying cell invasion

through basement membranes, cell invasive behaviors has been an area of intense study.

In this work I examine a developmentally regulated model of cell invasive behavior in

the nematode worm, C. elegans. In this system a single proto-epithelial cell remodels

basement membrane to connect two epithelial tissues, the uterus and vulva. Using this

model I identify a novel role for UNC-6/Netrin signaling during this process through basement membranes. I show that Netrin signaling is a third regulatory input for AC invasion that functions partially in parallel to fos-1a and the vulval signal. Further I link netrin signaling to the formation of invasive protrusions that penetrate basement membrane.