Molecular mechanisms underlying the formation of monosynaptic sensory-motor connections
In wild type mice (left), flexor Ia proprioceptive sensory (red) and extensor Ia proprioceptive sensory neurons (blue) connect to flexor motor neurons (MNs, red) and extensor MNs (blue), respectively. Sensory-motor connection specificity is determined by MN position-dependent (middle) and MN position-independent mechanisms (right). Abnormal MN positioning causes inappropriate sensory-motor connections in FoxP1 mutants (middle). In Sema3e and PlexD1 mutants (right), the absence of repulsion signaling causes inappropriate connections without MN position defects.