title: Marked increase in beta-tubulin mRNA expression during regeneration of axotomized retinal ganglion cells in adult mammals.
abstract: Changes in gene expression were investigated in axotomized CNS neurons under conditions that inhibit or permit regrowth of their damaged axons. Levels of mRNA encoding beta-tubulin, the 150 kDa neurofilament subunit (NF-M), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were examined by quantitative in situ hybridization of adult rat retinal ganglion cells (RGCs) after axotomy in the optic nerve or during regeneration in a peripheral nerve (PN) graft. Soon after optic nerve section beta-tubulin, NF-M, and GAPDH mRNA levels decreased and remained low during the 1 month studied. In these retinas beta-tubulin mRNA fell to approximately 50% of normal controls. However, in the PN-grafted retinas, where approximately 20% of the surviving axotomized RGCs regenerate their axons, there were "hot spots" of beta-tubulin mRNAs where neuronal levels were nearly 300% higher than in controls. By retrograde neuronal labeling these hot spots were shown to correspond to the injured RGCs that regrew their axons into the PN graft; beta-tubulin mRNA levels in nonregenerating RGCs of the same retinas averaged 63% of controls. We suggest that interactions of RBC axons and components of the grafts' non-neuronal environment play a key role in the over fourfold differences in beta-tubulin mRNA levels observed between injured and regenerating RGCs.
authors.affiliation: Centre for Research in Neuroscience, Montreal General Hospital Research Institute, Quebec, Canada.
authors.forename: L
authors.initials: L
authors.lastname: McKerracher
authors.forename: C
authors.initials: C
authors.lastname: Essagian
authors.forename: A J
authors.initials: AJ
authors.lastname: Aguayo
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D005260:Female; D015870:Gene Expression; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D009416:Nerve Regeneration; D016900:Neurofilament Proteins / Q000235:genetics; D009900:Optic Nerve / Q000378:metabolism / Q000502:physiology*; D010525:Peripheral Nerves / Q000502:physiology / Q000637:transplantation; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000502:physiology*; D014404:Tubulin / Q000235:genetics*
chemical_list: D016900:Neurofilament Proteins; D012333:RNA, Messenger; D014404:Tubulin; C061195:neurofilament protein M; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases