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Fig. 1. Axon outgrowth and cytoskeletal organization, but neither neuronal specification nor early stages of cellular polarization, were severely compromised with hnRNP K knockdown. (A) Immunostained optical section of a stage 40 Xenopus tadpole demonstrates suppression of hnRNP K expression on the injected side by hnRNP K MO (below dots). SC (inside dashed lines), spinal cord; arrowheads, hnRNP K staining of muscle nuclei on the uninjected side. (B-Db) Suppression of axon outgrowth on the injected side of stage 40 tadpoles [B(bottom),Cb,Db] revealed by immunostaining for the indicated axonal markers. A and B are horizontal and Ca-Db parasagittal sections. Arrowheads in Cb and in Da and Db indicate examples of atrophied axons and neuronal perikarya, respectively. Arrowheads in B indicate normally projecting motor axons on the uninjected side. (Ea-Gc) Organization of the indicated cytoskeletal polymers was severely disrupted in neurons of bilaterally injected hnRNP K MO (PK MO) cultures compared with those of control MO (Ea,Fa,Ga), which appeared normal. With hnRNP K MO, F-actin circumscribed perikarya, but was asymmetrically distributed (Eb,Ec); microtubules formed an anastomosing network (Fb,Fc); neuronal intermediate filaments were twisted and radiated outward in multiple directions (Gb,Gc). (Ha-Id) Double immunostaining for N-β tubulin and Par6 as indicated. With control MO (Ha,Hb), Par 6 staining was punctate and filled neuronal perikarya and axons (arrowheads, growth cone). With hnRNP K MO (Ia-Id), neuronal perikaryal microtubules (Ic,Id) were poorly organized and failed to correspond with an asymmetric hotspot of Par6 immunostaining (Ia,Ib). Scale bars: 100 μm for A-Db; 20 μm for Ea-Id. |
