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Figure 3 | Neural Development

Figure 3

From: The abdomen of Drosophila: does planar cell polarity orient the neurons of mechanosensory bristles?

Figure 3

The differentiative divisions. (a) Divisions that generate a bristle in the anterior domain (nomenclature from reference [22]), anterior to top, dorsal midline to left. The left side shows frames from a film and the right side shows a representation, with colours code as in Figures 1b and 4; shaft cell (sf), brown; socket cell (so), yellow; neuron (n), green; sheath cell (st), red. The film starts at 27 h APF with the division of the SOP and is timed as in [22]. The first division is oriented close to the AP axis, and generates PIIb and PIIa. PIIa gives the shaft and socket cell, while PIIb divides to gives rise to PIIIb and a small fifth or glial cell that migrates away quickly and posteriorly (see 5.00). PIIIb makes the neuron and sheath cell. Later, 6–7 h from the first cell division, the dendrite (white arrow) and axon grow out in anterior and posterior directions, respectively. This sequence of events is similar to the notum apart from an inconsistency with respect to the fifth cell. We saw the fifth cell migrating away from the cluster well before the axons extended (Figure 3a, 5:00) while Gho and colleagues reported that the fifth cell migrated away along an axon [22], although their images do not show this axon; but Fichelson and Gho [62] reported that the fifth cell migrates away and undergoes apoptosis, apparently in the absence of an axon. In Oncopeltus, the fifth cell disappears before axon outgrowth [12]. (b) The same sequence is followed by SOP cells in the posterior domain, but the cell positions and orientations are different: the small fifth cell here migrates anteriorly, the dendrite and axon grow out in posterior and an anterior directions, respectively. See the scheme in Figure 4.

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