Reggies/flotillins regulate retinal axon regeneration in the zebrafish optic nerve and differentiation of hippocampal and N2a neurons.
The reggies/flotillins--proteins upregulated during axon regeneration in retinal ganglion cells (RGCs)--are scaffolding proteins of microdomains and involved in neuronal differentiation. Here, we show that reggies regulate axon regeneration in zebrafish (ZF) after optic nerve section (ONS) in vivo as well as axon/neurite extension in hippocampal and N2a neurons in vitro through signal transduction molecules modulating actin dynamics. ZF reggie-1a, -2a, and -2b downregulation by reggie-specific morpholino (Mo) antisense oligonucleotides directly after ONS significantly reduced ZF RGC axon regeneration: RGC axons from reggie Mo retinas were markedly reduced. Moreover, the number of axon-regenerating RGCs, identified by insertion of A488-coupled dextran, decreased by 69% in retinas 7 d after Mo application. At 10 and 14 d, RGCs decreased by 53 and 33%, respectively, in correlation with the gradual inactivation of the Mos. siRNA-mediated knockdown of reggie-1 and -2 inhibited the differentiation and axon/neurite extension in hippocampal and N2a neurons. N2a cells had significantly shorter filopodia, more cells had lamellipodia and fewer neurites, defects which were rescued by a reggie-1 construct without siRNA-binding sites. Furthermore, reggie knockdown strongly perturbed the balanced activation of the Rho family GTPases Rac1, RhoA, and cdc42, influenced the phosphorylation of cortactin and cofilin, the formation of the N-WASP, cortactin and Arp3 complex, and affected p38, Ras, ERK1/2 (extracellular signal-regulated kinases 1 and 2), and focal adhesion kinase activation. Thus, as suggested by their prominent re-expression after lesion, the reggies represent neuron-intrinsic factors for axon outgrowth and regeneration, being crucial for the coordinated assembly of signaling complexes regulating cytoskeletal remodeling.
Munderloh
Christina
C
Department of Biology, University of Konstanz, D-78457 Konstanz, Germany.
Solis
Gonzalo P
GP
Bodrikov
Vsevolod
V
Jaeger
Friederike A
FA
Wiechers
Marianne
M
Málaga-Trillo
Edward
E
Stuermer
Claudia A O
CA
D000818:Animals; D000831:Animals, Newborn; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D003911:Dextrans; D015536:Down-Regulation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology*; D047468:Immunoprecipitation; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009416:Nerve Regeneration / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D020221:Optic Nerve Injuries / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D019188:Organ Preservation Solutions; D034741:RNA, Small Interfering / Q000378:metabolism; D012160:Retina / Q000473:pathology* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014162:Transfection / Q000379:methods; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000378:metabolism; D015027:Zebrafish; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism
D003911:Dextrans; D008565:Membrane Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D019188:Organ Preservation Solutions; D034741:RNA, Small Interfering; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; C485184:enhanced green fluorescent protein; C106354:flotillins; C115525:newcastle organ perfusion fluid; D049452:Green Fluorescent Proteins; D007334:Insulin-Like Growth Factor I; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins