Fig. 4: Requirement of LRP4 for maintaining muscle spindles.

a Illustration of breading Lrp4^f/f; HSA-Cre^ERT2 (imKO for short) mice and the schematic of tamoxifen administration, behavior tests and tissue collection. b Disrupted annulospiral endings in tamoxifen treated imKO mice (P60, P90). Representative images of EDL muscles in indicated groups, whole mount stained with NF/Syn (green) to label axon and axon terminals. Muscle spindle was determined by morphology. Square, images enlarged in right panel. Arrows, axon fragmentations; arrowheads, degenerated axon terminals. Scale bars, 100 µm and 10 µm. c–g Quantification of data in (b). c Reduced percentage of muscle spindles with annulospiral endings in tamoxifen treated imKO mice; t ₍₆₎ = 7.893, ***p = 0.0002; t ₍₆₎ = 21.614, ***p < 0.0001. n = 4 mice per group, unpaired two-tailed t test. d Decreased average spiral endings per muscle spindle (t ₍₃₀₎ = 4.915, ***p < 0.0001; t ₍₃₀₎ = 7.265, ***p < 0.0001). n = 16 muscle spindles from 4 mice per group, unpaired two-tailed t test. e, f Reduction of annulospiral ending area per muscle spindle (t ₍₃₀₎ = 6.215, ***p < 0.0001; t ₍₃₀₎ = 9.347, ***p < 0.0001) and intensity of muscle spindle in each group (t ₍₃₀₎ = 5.831, ***p < 0.0001; t ₍₃₀₎ = 9.215, ***p < 0.0001). n = 16 muscle spindles from 4 mice per group, unpaired two-tailed t test. g No difference of total muscle spindle in EDL muscle in each group. n = 4 mice per group, unpaired two-tailed t test. Data are shown as mean ± SEM. Source data are provided as a Source Data file.