Fig. 4: Molecular distinct pSN clusters segregate with MS or GTO afferents.

a Expression of Calretinin and tdT in ≥p56 lumbar DRG of PVRx3:tdT mice. b Percentage of CR⁺tdT⁺ neurons (of total tdT⁺) in adult PVRx3:tdT DRG. Mean percentage ± S.E.M. CR(L1-3): 11.6 ± 2.3%, n = 24 sections; CR(L4-5): 23.9 ± 1.9%, n = 40 sections, p < 0.001 (two-sided Mann–Whitney U test). c Expression of Pou4f3, Runx3, and tdT in ≥p56 lumbar DRG of PVRx3:tdT mice. Arrowheads indicate Pou4f3⁺Rx3⁺tdT⁺ neurons. d Percentage of Pou4f3⁺tdT⁺ neurons (of total tdT⁺) in adult PVRx3:tdT DRG. Mean percentage ± S.E.M. Pou4f3(T10): 13.9 ± 3.6%, n = 17 sections; Pou4f3(L5): 25 ± 3.2%, n = 78 sections. e Expression of Substance P and tdT in ≥p56 lumbar DRG of PVRx3:tdT mice. Boxed area is also shown in top right corner to illustrate expression of Substance P. f Percentage of Sub. P⁺tdT⁺ neurons (of total tdT⁺) in adult PVRx3:tdT DRG. Mean percentage ± S.E.M. SubP(L1-3): 13.8 ± 2.5%, n = 33 sections; SubP(L4-5): 9.0 ± 1.6%, n = 11 sections. g Expression of Calretinin (CR) (i, i′), Calbindin 1 (CB) (ii), and vGlut2 (iii) in GFP⁺ muscle spindle (MS) afferents of p12 (i, i′) or adult (≥p56) (ii, iii) muscle of PV:Cre; Mapt:lxp-STOP-lxp:mGFP-iNLZ (PV:GFP) mice. CR, CB, and vGlut2 expression is observed in GFP⁺ MS afferents that innervate the equatorial region of the muscle spindle. h Expression of vGlut1 and GFP in a muscle spindle (MS) of p18 EDL muscle of Calb2:Cre; Mapt:lxp-STOP-lxp:mGFP-iNLZ (Calb2:GFP) mice. Similarly as observed for Calretinin protein, in Calb2:GFP mice, expression of GFP labels MS afferents that innervate the equatorial region of the spindle. i Alkaline phosphatase (AP) labeling of GTO afferents in gluteus muscle of PV:Cre; Pou4f3:lxp-STOP-lxp:AP (PV/Pou4f3:AP) at p2 (i, ii), and at ≥p56 (iii, iv) mice. Dashed line in (i) indicates area of the myotentinous junction where GTOs reside. Arrow indicates muscle area where MSs are generally located. j Pcdh8 expression localizes to vGlut1⁺ GTO afferents in p12 gluteus muscle of wild type mice. k tdT⁺ MS afferents in EDL muscle of p20 Tac1:Cre; Ai14:tdTomato (Tac1:tdT) animals. l Summary of molecularly distinct pSN subclasses and their association with either MS (group Ia, putative group II) or GTO (group Ib) muscle receptors. In g–l, schematics indicate pSN subtype highlighted, and alleles used, in images below. Similar data obtained from at least three (a, c, e, g–i), two (k), or one (j) biological replicates. In boxplots (b, d, f), boxes indicate medians and 25th/75th percentiles, and whiskers extend to the furthest point <1.5 standard deviations from the mean. Scale 10 (a, c, e) 20 (g(ii), g(iii), h, j) or 50 (g(i)) μm.