FIGURE 8:

Crk is required for proper patterning of the embryonic CNS. (A–H, J–L) Stage 15 embryos, antigens and genotypes indicated. (I, M) Quantification of penetrance of phenotypes depicted. (A) mNG::Crk expressed at endogenous levels. Crk is enriched in CNS axons (cyan arrow) and midline glia (magenta arrow), suggesting Crk may play a role in axon pathfinding or function. (B, C) Representative images of CNS phenotypes, abl maternal, and zygotic null mutants. (D, E) CNS phenotypes of abl mutants expressing a form of Abl (AblΔCR1) that cannot bind to PXXP-dependent partners. Both can lead to the loss of commissures (B, D) or severe disruption of CNS patterning (C, E). (F–I) Representative images of range of CNS phenotypes in crkS-RNAi and crkW-RNAi embryos and quantification of their prevalence (I). In wild type, axons form a stereotypical ladder-like pattern with longitudinal axon bundles running anterior to posterior (cyan arrows, F–F’’) and commissural axon bundles crossing the midline at defined points in each body segment (magenta arrows, F–F’’). FasII-positive axons run in three parallel bundles on either side of the midline and do not normally cross the midline (F’’). Crk knockdown results in a range of CNS phenotypes including milder axon patterning defects and severe disruption of CNS patterning (G, H’’, I). (J–M) Representative images, different axon patterning defects observed after Crk knockdown and quantification of their prevalence. These include aberrant midline crossing (magenta arrows, G–G’’, L–L”), loss of longitudinal axons (yellow arrows, G–G’’, K–K”, L–L”), and loss of commissural axon bundles (white arrow, J–J’’). All scale bars = 50 µm.