Extrinsic regulation of injury/growth-related gene expression in the inferior olive of the adult rat.
Successful axon regeneration relies on the capability of the lesioned neurons to up-regulate a specific set of injury/growth-associated genes. In the adult central nervous system, the strength of the cell body response is generally related to the distance of the injury site from the perikaryon, being stronger for proximal lesions. Nevertheless, inferior olive (IO) cells react to injury and regenerate their axons even after distal transections. To investigate the mechanisms that regulate the IO growth properties, we examined the expression of injury/growth markers (nitric oxide synthase, growth-associated protein 43 and c-Jun) after target deletion or axotomy performed at different sites along the olivocerebellar pathway. Both axon injury and target loss disclose two subsets of IO neurons distributed within precise subnuclei: one subset up-regulates all markers in all conditions, whereas the other shows a mild c-Jun expression but remains unresponsive even after a very proximal axotomy. These observations indicate that distinct subpopulations of IO cells respond to different regulatory strategies. Unresponsive neurons appear insensitive to environmental positive or negative cues, suggesting that they are intrinsically unable to set up a cellular reaction to injury. In contrast, cell body changes in reactive neurons are elicited after the removal of retrogradely transported target-derived inhibitory signals. Target loss also induces degeneration of IO cells, whose survival remains partially dependent on Purkinje targets in adulthood. Thus, the intrinsic regenerative potential of a functionally homogeneous population is regulated by multiple mechanisms, specific for distinct neuronal subsets.
Buffo
Annalisa
A
Rita Levi-Montalcini Center for Brain Repair, Department of Neuroscience, University of Turin, C. Raffaello 30, 10125 Turin, Italy. annalisa.buffo@unito.it
Carulli
Daniela
D
Rossi
Ferdinando
F
Strata
Piergiorgio
P
D000818:Animals; D000911:Antibodies, Monoclonal / Q000633:toxicity; D001369:Axons / Q000378:metabolism / Q000473:pathology; D019771:Axotomy / Q000379:methods; D001426:Bacterial Proteins; D001930:Brain Injuries / Q000378:metabolism*; D002452:Cell Count; D002470:Cell Survival / Q000187:drug effects; D002531:Cerebellum / Q000293:injuries; D003078:Colchicine / Q000031:analogs & derivatives* / Q000633:toxicity; D019922:GAP-43 Protein / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D007074:Immunoglobulin G / Q000633:toxicity; D000922:Immunotoxins / Q000633:toxicity; D017403:In Situ Hybridization; D051379:Mice; D008817:Mice, Mutant Strains; D009699:N-Glycosyl Hydrolases / Q000633:toxicity; D009474:Neurons / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D009847:Olivary Nucleus / Q000166:cytology / Q000378:metabolism*; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics; D010940:Plant Proteins / Q000633:toxicity; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins; D013396:Suction / Q000379:methods; D013997:Time Factors
C085696:192 IgG-saporin; D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D019922:GAP-43 Protein; D007074:Immunoglobulin G; D000922:Immunotoxins; D010940:Plant Proteins; D016755:Proto-Oncogene Proteins c-jun; D054789:Ribosome Inactivating Proteins, Type 1; D019001:Nitric Oxide Synthase; D000587:Oxidoreductases Acting on CH-NH Group Donors; C109029:delta-1-piperideine-6-carboxylate dehydrogenase; D009699:N-Glycosyl Hydrolases; D000076985:Saporins; C012852:colchiceine; D003078:Colchicine