Figure 6.
Notch signaling attenuates JNK activity via Pak (A–C′) loss of Notch signaling as well as constitutive Pak activation result in clustered axons. Data shown: mean ± SEM. Scale bar: 20 µm. (D) Analysis of the number of medulla innervations under the following conditions: Control 12.33 ± 0.89 SD, NotchDN 17.95 ± 3.19 SD (p<0.05 to Control), Pak RNAi 10.1 ± 1.73 SD, Pakmyr 19 ± 1.8 SD (p<0.05 to control), bskDN 8.6 ± 1.26 SD, NotchDN and bskDN 6.3 ± 1.57 SD (p<0.001 to NotchDN), NotchDN + Pak RNAi 9.25 ± 2.38 SD (p<0.001 to NotchDN), and Pakmyr + bskDN 8.5 ± 2.35 SD (p<0.001 to Pakmyr). (E) Schematic of the interaction between Notch, Pak and JNK signaling to determine axonal target choice. (F) A subset of DCNs marked with GFP (green) and pucLacZ (red) shown in the left panel. Analysis of pucLacZ in control and gain of Notch function DCNs (3.04 ± 0.24 SD vs 1.86 ± 0.35 SD, n = 3, (p=0.01, Student's t-test)). pucLacZ level within the DCNs were normalized by measurements of pucLacZ level of the entire image except the DCNs. (G) The effects of Notch gain of function (by transfection of NICD) on Pak expression and JNK activity in Drosophila neuronal cell line DmBG2-c3. Western blot and quantification of the effects on Pak (1.0 ± 0.0 vs 0.628 ± 0.05 SD [p<0.001] Student's t-test) and phospho-JNK (active JNK) levels (1.0 ± 0.0 vs0.63 ± 0.129 SD [p<0.001, Student's t-test]). DCN: dorsal cluster neurons; NICD: intracellular domain of Notch; SD: standard deviation; SEM: standard error of the mean.