Figure 6. Loss of mec-17 Causes Microtubule Instability and Axon Fragility.

(A) A representative image of PLM in a L4 WT animal carrying the Pmec-4::ebp-2::GFP transgene that highlights the 25 μm region of interest (ROI) analyzed in the kymograph shown below the image. Schematic adjacent to kymograph illustrates how comets were traced and measured for growth length and duration. White arrows point to comets growing in the anterograde direction.

(B) Representative image of EBP-2::GFP expressed in PLM of a mutant mec-17(ok2109) L4 animal, with an increased number of microtubule comets, as evident in the kymograph below the image. White arrows point to comets growing in the anterograde direction; red arrows to those in the retrograde direction. For both (A) and (B), the scale bar in the images represents 10 μm; scale bars in the kymographs represent 10 μm for the x axis, and 10 s for the y axis.

(C) Mutation of mec-17(ok2109) causes a significant increase in the number of EBP-2::GFP comets compared to WT in L4 and 3-day-old adult animals. n = 15 animals for WT, and n ≥ 11 for mec-17(ok2109).

(D) EBP-2::GFP comets grow significantly more in the retrograde direction in both L4 and 3-day-old adult mec-17(ok2109) mutants compared to WT. n ≥ 25 comets for WT and n ≥ 69 for mec-17(ok2109).

(E) mec-17(ok2109) animals were grown on control agar containing 1% DMSO or agar containing either 1 μM paclitaxel (microtubule stabilizer) or 0.1 M colchicine (microtubule destabilizer) and scored as 2-day-old adults.

(F) Penetrance of axonal degeneration in 3-day-old adult coel-1(gk1236), mec-17(ok2109), or coel-1; mec-17 double mutants.

(G) Animals carrying the ky850 or mec-17(ok2109) mutations were paralyzed by microinjection of unc-54 dsRNA and the penetrance of breaks compared to that in nontreated animals.

The error bars represent SE (C and D) and SE of proportion (E–G); *p < 0.05; **p < 0.01; ***p < 0.001; n ≥ 100 animals for (E–G).