Fig. 4: In vitro reconstitution of the muscle spindles. | Nature Communications

Fig. 4: In vitro reconstitution of the muscle spindles.

From: Frataxin gene editing rescues Friedreich’s ataxia pathology in dorsal root ganglia organoid-derived sensory neurons

Fig. 4

a Co-cultures of DRGOs and intrafusal muscle fibers (IFFs) at DIV 7 with single axonal projections contacting IFFs visualized by immunofluorescence staining for the intrafusal muscle fiber marker S46 (red), and the neuronal protein ßIII-Tubulin (green). Scale bar, 50 µm. b Enlarged view of the boxed area in a reveals the annulospiral wrapping of the axonal terminal around the multinucleated intrafusal muscle fiber within the central domain where nuclei are concentrated (blue, nuclear staining with Hoechst). Scale bar, 10 µm. c Electron microscopy (EM) imaging showing an axonal process (blue) which is wrapping a segment of the intrafusal muscle fiber (red). Scale bar, 1 μm. d–k Calretinin (CALB2) (d–g) and vGLUT1 (h–k) staining (arrowheads) along the NF200 + annulospiral axonal terminals of DRGOs in co-cultures with intrafusal muscle fibers (IFFs) stained with S46 at DIV 50. Scale bar, 10 μm. l Electron microscopy imaging showing an invaginating clathrin-coated vesicle (arrowhead) within the axonal terminal. Scale bar, 100 nm. m, n Immunofluorescence for the synaptic vesicle markers Synapsin and vGLUT1 (green) within axonal fascicles labeled by NF200 (red). Scale bar, 5 μm.

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