Drosophila Growth Cones Advance by Forward Translocation of the Neuronal Cytoskeletal Meshwork In Vivo
Figure 1
Drosophila neurons grow at physiological rates in vitro.
(A) Coomassie stain of DECM purified from Kc167 conditioned media. Bands identified as Laminin A, Tiggrin, Laminin B1, and Laminin B2 by mass spectroscopy. Unsequenced band at 50 kDa corresponds to glutactin based on previous reports [44]. Phase images of Drosophila neurons grown in vitro on (B) poly-ornithine and (C) DECM. Axonal length at 24 hours increases with concentrations of DECM at 2 µg/ml and higher (D). The numbers in the bars in (D) represent n for each group. The graph in (E) shows axonal initiation is asynchronous, occurring over a period of ~12 hours, and is not substrate dependent. The arrow marks the time point where 50% of the neurons had initiated axons. Representative examples of growth cone position over time are shown for neurons grown on (F) poly-ornithine and (G) DECM. By aligning individual growth cone positions so initiation is at t = 0, accurate depictions of cone advance can be more clearly seen. (H) poly-ornithine alignment, (I) DECM alignment. Averaging axonal length over time without accounting for differences in initiation (J) yields rates of elongation similar to previous reports, whereas analysis of synchronized average axonal length (K) reveals elongation occurs at rates similar to those observed in vivo. All error bars are 95% CI. Scale bar = 70 µm.