Figure 7. Ret and Gfrα3 are Required for MN Pool Differentiation and Connectivity.
(A) Pea3 expression is reduced in brachial LMC neurons in Ret mutants at e12.5. (B) Quantification of the number and distribution of Pea3+ MNs in Ret−/− and control mice. (C) The number of Scip+ MNs increases in Ret−/− mice. (D) Quantification of the number and distribution of Scip+ MNs. (E,F) Wholemount GFP staining showing defects in CM muscle innervation in Ret−/− embryos (arrow) at e12.5. (G,H) Forelimb innervation at e13.5 showing failure of ulnar MNs to project distally in Ret−/− embryos (arrow). Arrows in control diagram indicate region where nerve diameters were measured. (I–K) Disorganization of MNs in Ret−/− mice shown by retrograde labeling of MNs projecting along the medial anterior thoracic, median and ulnar nerves. (L,M) Forelimb innervation pattern in Gfrα3+/+ and Gfrα3−/− mice at e13.5 showing thinning of the median and ulnar nerves. Scale-bars represent 500 μm. (N) Quantification of muscle nerve diameters expressed as a ratio between the radial and ulnar nerves in Ret and Gfrα3 mutants and controls at e13.5. See also Figure S7.
