Every so often, a paper comes along that brings clarity to an issue. Clarity is not necessarily a final resolution, but rather a conceptual framework for productively addressing that issue. Such a paper could be based on a breakthrough discovery, an intriguing observation, a flash of intuition, or a systematic analysis. An excellent example of the latter is in this issue of The Journal of Cell Biology (Hotary et al. 2000). With a deceptively simple experimental layout, Hotary et al. 2000 explore the relative role of soluble versus membrane-anchored matrix metalloproteinases (MMP) in tissue morphogenesis. In their in vitro morphogenesis and matrix invasion models, the conclusion is clear cut: membrane-anchored (MT-MMPs), not soluble MMPs, effectively regulate cell migration through extracellular matrix and affect self-organization of cells into tubular structures (Fig. 1).
Cell migration through the...
