Fig. 4: Directionality differs among SGN processes growing through similar regions.
From: Neuronal processes and glial precursors form a scaffold for wiring the developing mouse cochlea
a–d Frames from movies of sparsely labeled tdTomato+ SGNs from Neurog1CreERT2;Ai14 animals as they grow in Region 1 (a) (N = 3 cochleae) (Supp. Movie 5) or Region 2 (c) (N = 3 cochleae) (Supp. Movie 6), with directionality quantified in (b) and (d). In Region 1 (a), a border SGN extends highly branched processes (orange dots) whereas a peripheral process from a rear cell (cell body out of view) (blue arrows) follows a rapid and directed path. Quantification of 25 border and 24 rear cells (b) confirmed that peripheral processes from rear cells are significantly more directed. In Region 2 (c), an SGN process at the wavefront (orange arrowheads) extends many branches and makes little progress. An SGN process arriving from behind (blue arrowheads) moves rapidly and is capped by a large, unbranched growth cone. Quantification (d) revealed significantly more directed growth of processes behind the wavefront (n = 17 wavefront processes and 23 trailing processes). Note that not all SGN processes are labeled, so it is not possible to detect fasciculation events reliably. Raw data are plotted, with mean ± SEM superimposed. Significance was assessed using an unpaired, two-tailed t-test. Directionality: border vs rear, P < 0.0001; wavefront vs behind, P < 0.0001. Source data are provided as a Source data file. Time is indicated in hh:mm. Scale bar =  10 µm (a, c).
