Tissue-specific activities of the Fat1 cadherin cooperate to control neuromuscular morphogenesis
(A, B) The nerve pattern was analyzed by IHC with antibodies against neurofilament in E12.5 (A) to E12.75 (B) wild-type and Fat1-/- embryos. Embryos were cut in half, cleared in BB-BA, and flat-mounted. Upper panels are low-magnification images of the left flank, showing the whole trunk. Lower panels show high-magnification views of the area containing the CM muscle. The area covered by CM-innervated axons is highlighted in white (middle panels). Axons of vertically oriented thoracic spinal nerves have been manually removed by dissection in the lower panels to improve visibility of CM axons. Inserts in the lower panels represent higher magnification of the area in the yellow squares. (C) Quantifications of the relative expansion of the area covered by CM-innervating axons. Upper plot: for each embryo side, the area covered by CM-innervating axons is plotted relative to the length of a thoracic nerve (T10, from dorsal root origin to ventral tip). Arrows point the stages of representative examples shown in (A) and (B). Bottom plot: for each embryo, the CM-innervated area/T10 length was normalized to the median ratio of control embryos, by size range. Blue dots: Fat1+/+ (n = 35, same sample set as in controls of S3 Fig); red dots: Fat1-/- (n = 12). Underlying data are provided in S1 Data. Scale bars: 500 μm (large images); 100 μm (inserts in lower panels). BB-BA, benzyl-benzoate/benzyl-alcohol mix; CM, cutaneous maximus; IHC, immunohistochemistry; T10, 10th thoracic nerve; WT, wild-type.