Figure 5.

Loss of synaptic contacts between PMC neurons and diaphragms in Hox5^MNΔ mice. (a– d) Analysis of diaphragm innervation patterns at e18.5. (a–b) Diaphragms of Hox5^MNΔ mutants display a marked reduction in terminal branches and neuromuscular synapses, as revealed by neurofilament and bungarotoxin staining (n=10). (c–d) While the phrenic nerve establishes contacts with the muscle and forms a primary branch, secondary and tertiary branches fail to form. As a consequence the number of synapses formed at the diaphragm muscle is dramatically reduced in Hox5^MNΔ mutants. Scale bar=500 μm. Images shown are tiled composites of individual panels. The pattern of forelimb innervation was not appreciably affected in Hox5^MNΔ embryos, and the biceps, a muscle supplied by Hox5+ LMC neurons, was innervated normally (Supplementary Fig. 5a–d).