We used the developing mouse diaphragm as a model for assessing axonal guidance, where motor axons first reach the diaphragm between E11 12, but continue to branch and respond to guidance cues up to E15, when the mature innervation pattern is reached [40], [41].
Furthermore, the outgrowth was similarly reduced in this condition but leading processes still grew preferentially toward the Netrin-1 source in the proximal quadrant rather than in the distal quadrant (Fig. 4D, E, and F), indicating that TTL−/− neurons can still respond to guidance cues.
The pathfinding errors seen in ioFL-expressing cells suggest that CaP axons misinterpret or fail to respond to guidance cues.
Therefore, by using Dll4+/− mice retinas in the ICR strain, it was shown that absence of one Dll4 allele leads to an increase of endothelial tip cells that sense and respond to guidance cues during angiogenesis [ 90- 92].
Developing axons possess a considerable degree of functional autonomy, and axons severed from their cell bodies can respond to guidance cues in culture (Campbell and Holt, 2001) and navigate accurately in vivo (Harris et al., 1987).
However, notable differences were observed between age groups of schoolchildren, with 1st grade schoolchildren in particular being enthusiastic about the HWWS; they were observed to enjoy playing and competing for water and soap, being very fast and eager to respond to guidance on HWWS of schoolteachers, e.g. before going to class in the morning and being exited each time they lined up for HWWS.
As the embryonic renal tubules assume their mature shape they interact with other tissues, responding to Dpp guidance cues as they take up their characteristic positions in the body cavity (Bunt et al., 2010).
Although previous studies have shown that MTs are required for axon outgrowth (Tanaka et al., 1995) and turning behaviors (Tanaka and Kirschner, 1995; Buck and Zheng, 2002) few studies of mammalian growth cones responding to growth and guidance cues have visualized changes in MT organization with high resolution live cell imaging (Kalil and Dent, 2005; Dent et al., 2011).
The treatment of moving sources that respond to guidance molecules they themselves secrete is mathematically challenging and will be dealt with in the Appendix.
