Axonal Projections in the Spinal Cord after DiI Labeling of DRG at P0
(A) Rescued DRG proprioceptive neurons fail to properly innervate motor neurons in double KOs. Instead, some axons are directed towards the ventral midline; they cross the midline and branch.
(B) Schematic drawing of the monosynaptic reflex arc as it normally develops. Small black dots represent NT-3 released centrally by the motor neurons and peripherally by the muscle spindles.
(C) High-power magnification of the inset in (A). Arrow points to the midline, and arrowheads point to synaptic bouton-like structures.
Scale bar: 1 mm (A), 400 μm (C).