Type IV collagen provides BM with tensile strength, which allows BM to structurally support tissues and resist mechanical forces ( Fidler et al., 2018). Type IV collagen is a large protein comprised of two α1-like and one α2-like chains, and these heterotrimers cross-link to form a grid, which is thought to be connected to the laminin network through bridging molecules ( Hohenester and Yurchenco, 2013). Once secreted, laminin associates with cell surface receptors and self-assembles into a sheet-like network.
Laminin is comprised of an α, β, and γ subunit. The two core BM matrix components are the heterotrimeric proteins laminin and type IV collagen. BM provides tissues with structural support, barrier functions, and signaling platforms ( Morrissey and Sherwood, 2015 Jayadev and Sherwood, 2017 Pozzi et al., 2017). eLife assessmentīasement membrane (BM) is a planar, cell-associated extracellular matrix (ECM) that underlies or surrounds most tissues. These results uncover a synchronizing mechanism for robust adhesion during tissue connection, where collagen both affixes the linkage and signals to both tissues to bolster their adhesion. RNAi depletion, genome editing, and photobleaching experiments revealed that DDR-2 signals through LET-60/Ras to coordinately strengthen an integrin adhesion in the utse and seam that stabilizes their connection. Through genetics, quantitative fluorescence, and cell-specific molecular disruption, we show that type IV collagen, which fastens the linkage, also activates the collagen receptor discoidin domain receptor-2 (DDR-2) in both the utse and seam. Here, we have investigated this question using the Caenorhabditis elegans utse-seam tissue connection that supports the uterus during egg-laying. Yet, how cells achieve synchronized adhesion to connect tissues is unknown. Cell adhesion at these connections must be robust and balanced to withstand independent tissue movement.
Separate tissues connect through adjoining basement membranes to carry out molecular barrier, exchange, and organ support functions.
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