Extracellular Matrix Dynamics in Early Development

The extracellular matrix (ECM) is an inherently dynamic structure during development. Large-scale tissue movements sweep the ECM to distant positions during early embryogenesis; furthermore, the previously assembled ECM filaments are extensively reused during later organogenesis. Thus, some organs, such as the heart, inherit previously assembled ECM filaments. This review focuses on the macro-assembly dynamics of fibronectin and fibrillin-2 in avian embryos. Both ECM proteins are ubiquitous in vertebrate embryos at the earliest stages of development. Recent studies compared the movement of these two ECM components and suggested that the ECM moves as a composite material, whereby distinct molecular components as well as spatially separated layers exhibit similar displacements. Utilizing advances in microscopy and high-resolution particle image velocimetry algorithms, two ECM filament relocation processes can be distinguished—each operating on different length scales. First, ECM filaments are moved by large-scale tissue motion, which rearranges major organ primordia within the embryo. The second type of motion, on the scale of the individual ECM filaments, is driven by local motility and protrusive activity of nearby cells. Both kinds of motion contribute substantially to the establishment of normal ECM structure, and both must be taken into account when attempting to understand ECM macro-assembly during embryonic morphogenesis. ECM filaments also fluctuate locally—likely reflecting pulsatile cell contractility in the associated tissues. Suppression of these fluctuations by temporal averaging yields a persistent movement pattern that is shared among embryos at equivalent stages of development. A. Czirok (*) Department of Anatomy and Cell Biology, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160, USA Department of Biological Physics, Eotvos University, Budapest, Hungary e-mail: [email protected] B.J. Rongish • C.D. Little Department of Anatomy and Cell Biology, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160, USA D.W. DeSimone and R.P. Mecham (eds.), Extracellular Matrix in Development, Biology of Extracellular Matrix, DOI 10.1007/978-3-642-35935-4_2, # Springer-Verlag Berlin Heidelberg 2013 19 Recent studies comparing the motion of embryonic mesenchymal cell populations (newly ingressed mesodermal, pre-somitic, endothelial, and endocardial) all found that the gross displacement of these cells is to a large extent shared by the surrounding ECM. The result being that active motion relative to the local ECM scaffold is more random than previously appreciated. A future understanding of ECM assembly thus requires the study of the complex interactions between biochemical assembly steps, local cell action and the biomechanics of tissue motion.