Figure 5. The 2D WTMM Method Is Used to Quantify Cellular Structure within a Lattice, and Indicates that Cellular Organization Increases during Muscle Morphogenesis.

A) Description of how the 2D WTMM formalism quantifies structure. The starting image is of elongating muscle precursor cells stained for β-catenin to outline cells. B) Short muscle precursor cells have almost all WTMMM vector arrows pointing in random directions, indicating that there is only a small departure from isotropy (isotropy means randomly structured). C) Organization increases as muscle cells begin to elongate. Note more green arrows pointing either up or down in C than B. D) Organization continues to increase during the myotube formation phase. E) Organization is readily apparent when myotubes have formed. Note that most of the green arrows are pointing either up or down indicating high levels of organization. F) Averaged P_a(A) for one particular size scale (a∼7 µm) for the myotube stage (lime green curve), the forming myotube stage (dark green curve), elongating precursor stage (blue curve), short precursor (red curve) as well as for the isotropic fBm surfaces analyzed for calibration purposes (black curve fluctuating around π/2). Also shown is the flat 1/2π curve that would be obtained for a purely theoretical isotropic process (flat pointed line at 1/2π). G) The anisotropy factor F_a was averaged over all size scales analyzed. An indicator of organized structure, it shows significantly distinct values for all stages of developing muscle cells.