Protein synthetic machinery and mRNA in regenerating tips of spinal cord axons in lamprey.
Polyribosomes, mRNA, and other elements of translational machinery have been reported in peripheral nerves and in elongating injured axons of sensory neurons in vitro, primarily in growth cones. Evidence for involvement of local protein synthesis in regenerating central nervous system (CNS) axons is less extensive. We monitored regeneration of back-labeled lamprey spinal axons after spinal cord transection and detected mRNA in axon tips by in situ hybridization and microaspiration of their axoplasm. Poly(A)+mRNA was present in the axon tips, and was more abundant in actively regenerating tips than in static or retracting ones. Target-specific polymerase chain reaction (PCR) and in situ hybridization revealed plentiful mRNA for the low molecular neurofilament subunit and β-tubulin, but very little for β-actin, consistent with the morphology of their tips, which lack filopodia and lamellipodia. Electron microscopy showed ribosomes/polyribosomes in the distal parts of axon tips and in association with vesicle-like membranes, primarily in the tip. In one instance, there were structures with the appearance of rough endoplasmic reticulum. Immunohistochemistry showed patches of ribosomal protein S6 positivity in a similar distribution. The results suggest that local protein synthesis might be involved in the mechanism of axon regeneration in the lamprey spinal cord. J. Comp. Neurol. 524:3614-3640, 2016. © 2016 Wiley Periodicals, Inc.
Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140. jinliqin@temple.edu.
Li-Qing
LQ
Jin
Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140.
Cynthia R
CR
Pennise
Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140.
William
W
Rodemer
The Children's Hospital of Philadelphia, 1108 Pine Street, Philadelphia, PA, 19107.
Kristen S
KS
Jahn
Shriners Hospitals Pediatric Research Center, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140. mselzer@temple.edu.|Department of Neurology, Lewis Katz School of Medicine at Temple University, 3500 North Broad Street, Philadelphia, PA, 19140. mselzer@temple.edu.
Michael E
ME
Selzer
D000199:Actins / Q000378:metabolism; D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D015153:Blotting, Western; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D018870:Endoplasmic Reticulum, Rough / Q000378:metabolism / Q000648:ultrastructure; D029941:Fish Proteins / Q000378:metabolism / Q000648:ultrastructure; D017403:In Situ Hybridization; D007798:Lampreys / Q000378:metabolism*; D008854:Microscopy, Electron; D009416:Nerve Regeneration / Q000502:physiology*; D016900:Neurofilament Proteins / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011132:Polyribosomes / Q000378:metabolism / Q000648:ultrastructure; D014176:Protein Biosynthesis / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D038601:Ribosomal Protein S6 / Q000378:metabolism / Q000648:ultrastructure; D013116:Spinal Cord / Q000378:metabolism* / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism; D014746:Vimentin / Q000378:metabolism
D000199:Actins; D029941:Fish Proteins; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D038601:Ribosomal Protein S6; D014404:Tubulin; D014746:Vimentin; C044882:neurofilament protein L
axons; lamprey; mRNA; regeneration; ribosomes; spinal cord