Article Figures & Data
Figures
- Figure 1.
The Atoh1Cre/+ knock-in mouse line labels the IH and IF MN pools. A, B, Injection of the retrograde tracer CTB-488 into the forepaw and hindpaw labels the IH and IF MN pools, which are labeled with tdTomato (TOM) in Atoh1Cre/+ knock-in mice. MN pools are identified with ChAT antibody. Arrows, CTB+TOM+ChAT+; arrowheads, CTB–TOM+ChAT+. C, Diagram of CTB-488 injections into the IH and IF MN pools, which are located at T1 and L6. D, Injection of CTB-488 into the TA, GS, Q, and Ad muscles retrogradely labels those MN pools, which are sparsely labeled with TOM in Atoh1Cre/+ knock-in mice. Arrows, CTB+TOM+ChAT+; arrowheads, CTB–TOM+ChAT+. E, Percentage of the IH, IF, TA, GS, Q, and Ad MN pools that are labeled TOM+ in Atoh1Cre/+ knock-in mice. F, G, Some of the TOM+ IH MNs and IF MNs are fast twitch MNs (MMP9+). Arrows, MMP9+TOM+; arrowheads, MMP9–TOM+. H, Atoh1-lineage neurons in the intermediate spinal cord have extensive overlap in Atoh1P2A-FLPo; EGFP mice crossed to Atoh1Cre; tdTom mice (arrowheads, GFP+TOM+, white). However, IH and IF MNs are only labeled in the Atoh1Cre/+ mice (TOM+) and not in the Atoh1P2A-FLPo/+ mice (GFP–; inset). P, postnatal; T, thoracic; L, lumbar. Scale bars: 100 μm.
- Figure 2.
Distribution of MNs labeled in the Atoh1Cre/+ knock-in mouse throughout the spinal cord. Representative images throughout the rostral-caudal axis of Atoh1Cre/+ knock-in mice crossed to the TOM reporter mouse show that TOM labels MNs mainly in the IH and IF MN pools (yellow dashed lines) with sparser labeling of MNs in other MN pools (arrows). Some MN pools have no TOM+ expression (arrowheads). TOM+ChAT+ cells in the IML are sympathetic pre-MNs (asterisks). IML, intermediolateral nucleus; ICo, intercostal; ThAb, thoracic abductor; Q, quadricep; Gl, gluteus; Hm, Hamstring. Scale bars: 100 μm.
- Figure 3.
The Atoh1Cre/+ knock-in mouse labels IH and IF MN pools postnatally. A–A’’’, TOM+ labeling of the IF MN pool at several postnatal time points. TOM+HB9+ neurons, arrows. In A, CTB (blue) was injected into the hindpaw to identify the IF MN pool. In A’–A’’’, the IF MN pool was identified by location in the lumbar spinal cord. B, Percentage of TOM+ neurons in the IH or IF MN pools at several postnatal time points. The IH and IF MN pools were identified by CTB injection into the forepaw and hindpaw at P0 and tissue harvested 3 d later for the P3 time point. IH and IF MN pools for P7, P15, and P22 were identified by location in the lumbar spinal cord. C–C’, At E14.5, TOM+ neurons are CPNE4– and FIGN–. D–D’, At P6, TOM+ neurons are CPNE4+ and FIGN+ (arrows). Scale bars: 100 μm.
- Figure 4.
Both α-MNs and γ-MNs are labeled in the Atoh1Cre/+ knock-in mouse. A, TOM+ MNs in the IF MN pool are NEUN+ (arrows) and have closely apposed VGLUT1+ boutons (gray arrows). B, Some TOM+ IF MNs are also ERR3+ (arrow). C, Percentage of the TOM+ MNs in the IH and IF that are ERR3+ (γ-MN marker) or NEUN+ (α-MN marker). D, Percentage of the IH and IF MN pools that are ERR3+. E–E’’, TOM+ axons in the hindpaw lumbrical muscle show the NMJ innervating extrafusal muscle (E’, arrows, BTX+STX1+TOM+). TOM+ axons also innervate the intrafusal muscle spindle (E, open arrowhead; E’’, arrows, BTX+STX1+TOM+). Arrowheads indicate motor endplates that are TOM-. Scale bars: 100 μm; 10 μm (A, inset).
- Figure 5.
Labeling of IH and IF MNs using an intersectional genetic approach. A, ChatIRES-FLPo/+ mice crossed to a FLPo-dependent tdTomato reporter labels the IF MN pool, identified by injection of CTB into the hindpaw. ChAT Ab identifies the entire MN pool. B, The IF MN pool is sparsely labeled using an intersectional cross (AtohCre/+; ChatIRES-FLPo/+). C, Percentage of the IH and IF MN pools labeled in ChatIRES-FLPo/+ mice and AtohCre/+; ChatIRES-FLPo/+ mice. IH and IF MN pools were identified by retrograde labeling with CTB. Scale bars: 100 μm.
In this issue
