题目：BREACHING THE BASEMENT MEMBRANE: ANCHOR CELL INVASION IN C. ELEGANS

报告人：David R. Sherwood, Ph.D.,Assistant Professor of Biology,Department of Biology,Duke University

时间：2010年10月12日上午10点

地点：遗传发育所B210报告厅

联系人：杨崇林 (010-64889375)

摘要：

Cell invasive behavior is critical in many developmental processes and is co-opted by metastatic cancer cells. The cellular and molecular mechanisms that control invasive behavior are poorly understood in large part because of the challenge of studying this dynamic process in vivo. My laboratory’s research focuses on characterizing anchor cell (AC) invasion into the vulval epithelium in C. elegans, where single-cell visual and genetic in vivo analyses can be combined. During C. elegans larval development, the AC, a specialized gonadal cell, breaches the gonadal and ventral epidermal basement membranes (BMs) to contact the central vulval precursor cells to initiate uterine-vulval connection. We have found that approximately six hours prior to invasion, a specialized invasive cell membrane, rich in F-actin and actin-regulators, is established within the AC through a coordination of netrin and integrin signaling at the interface of the AC and BM.　 Using high resolution imaging of translational GFP and mCherry fusions to simultaneously observe components of the invasive membrane and BM, we have identified actin-based membrane protrusions that mediate the initial stages of breaching the BM by the AC. These invasive membrane structures are similar to the invadopodia observed in highly metastatic cancer cells in vitro, and represent the first in vivo documentation of their existence.　 Time-lapse analysis studies show that these invadopodia are highly dynamic, with half-lives on the order of minutes. Strikingly, when one breaches the BM, the others rapidly disappear, and a single narrow cellular protrusion develops from this invadopodia that crosses the BMs. Over time, this process broadens to the width of the AC. While it is generally assumed that bulk proteolytic degradation serves as the predominant mechanism to create gaps in BM during invasion, photoconversion experiments using the photoconvertible fluorescent protein Dendra tagged to the BM component laminin indicate that the basement membrane is predominantly removed by pushing it aside. Taken together our studies are building a molecular and cellular framework by which cells breach BM, offering new and unexpected insight into this fundamental biological process.