Figure 2: Dendritic dynamics vary systematically with soma position in spinal cord.

(a,b) Images of a ventral motoneuron expressing mGFP at the first two consecutive time points (0 and 5 min). (c) Overlaid image of a and b. Arrows point to filopodial extensions. (d) Reconstruction (in white) of dendritic extensions over a 30-min period in the same neuron. (e,f) Images of a dorsal motoneuron at the first two consecutive time points (0 and 5 min). (g) Overlaid image of e,f. Arrows point to filopodial extensions. (h) Reconstruction (in white) of the neuron’s filopodial extensions over a 30-min period. (i,j) Quantification of filopodial extensions and retractions between consecutive time points for 34 mGFP expressing motoneurons. Each row represents a single cell and the rows are arranged from bottom to top based on the ventral to dorsal position of the cell in the spinal cord. Each column represents the total length of filopodial extension between two consecutive time points normalized to the dendritic arbour length of that cell. Colour map is on the right. (k) Plot of cell body position versus length of dendritic arbour that remained unchanged over the entire imaging period for each motoneuron. Locations are normalized with respect to the dorsal (one) and ventral (zero) edges of spinal cord in all figures. (l) Plot of cell body position versus total number of filopodia extended in the 30-min imaging period. (m) Plot of position versus the summed length of all filopodial extensions over the entire imaging period. (n) Plot of soma position versus the normalized filopodial dynamics, which were calculated by dividing the sum of all filopodial extensions for a cell by the stable dendritic arbour length of that cell. Scale bar, 10 μm in a–h.