Proprioceptive sensory neurons and muscle spindles are marked reduced in adult Swl/+ mice. Proprioceptive sensory neurons and muscle spindles are marked reduced in adult Swl/+ mice. A, Mature muscle spindles, stained by S46 antibody (green) and collagen IV antibody (ColgIV, red), are primarily absent in the Swl/+ hindlimbs. B, Quantitative analysis of muscle spindles demonstrates that Swl/+ mice have 88% fewer muscle spindles than those of WT mice. *p < 0.01 (Student's t test). C, Representative immunostained sections show that proprioceptive neurons (PV+) are more severely compromised than nociceptive neurons (CGRP+) in the lumbar Swl/+ DRGs. Scale bars (in A, C), 100 μm. D, Quantitative analysis indicates that the total number of DRG neurons is significantly reduced in the lumbar (L4) DRGs but is not significantly reduced in the cervical (C4) DRGs of Swl/+ mice. *p < 0.01 (Student's t test). E, Quantitative analysis of subpopulation in the L4 DRGs demonstrates that the number of proprioceptive neurons (PV+) is reduced by 69% in Swl/+ mice (*p < 0.01, Student's t test), whereas only a 31% reduction of the number of nociceptive neurons (CGRP+) is detected in Swl/+ mice (p > 0.05, Student's t test). Xiang-Jun Chen et al. J. Neurosci. 2007;27:14515-14524 ©2007 by Society for Neuroscience