• type Ia proprioceptive sensory neuron projections are disrupted and exhibit arrest at E15.5 as they reach the brainstem or ventral spinal cord in the medial spinal cord adjacent to the central canal and entire rostral-caudal extent of the spinal cord that persists through fetal development until P8 compared to in control mice
• type Ia proprioceptive sensory neuron projections fail to form terminal arbors
• mice exhibit defects in a second population of sensory neurons with few axons of the T12 dorsal root ganglion that cross the midline and only rare occurrences of axons that reach the proper contralateral target compared with control mice
• whisker axons have sparse arbors that fail to reach the correct target region in the bed nucleus of the stria terminalis (BSTC) without extensive branching
• however, mice exhibit normal growth of the sensory axons in the spinal cord and neuron targeting of nociceptive sensory axons in laminae I/IIi/IIo
• however, mice exhibit normal Pv+ proprioceptive axons growth into fore and hind limb muscles, trunk sensory axons form normal disc shaped endings on Merkel cells in the epidermis and axons in the deep vibrissal nerve that innervate whisker follicles