Orientation, Clustering, and Compaction of Nascent Muscle Fibers Prefigure Muscle Bundle Formation and Are Disrupted Following Conditional Deletion of Tbx5
(A–D) Dorsal view of E11.5 (A), E11.75 (B), E12.0 (C), and E12.5 (D) control forelimbs with muscle cells detected by Myogenin in situ hybridization to illustrate the region analyzed by immunohistochemistry in (E)–(K). Dotted line squares in (A)–(D) show the approximate area where cell vectors shown in (E)–(H) have been drawn.
(E–K) Projection of cell vectors drawn from a Z series of confocal scans of limbs at the stages indicated, stained by whole mount immunohistochemistry for myogenin and myosin in control E11.5 (E), E11.75 (F), E12.0 (G), E12.5 (H), and Tbx5lx/lx;Osr2Cre mutant E11.5 (I), E12.0 (J), and E12.5 (K). The vector lines outline cell orientation.
(E'–K') Projection of the color-coded cell vectors for control (E'–H') and mutant (I'–K') forelimbs. Each cell vector has been assigned a color value corresponding to a range of angle values from 0° to 180°, shown on the rainbow ruler.