Transgenic labeling of the corticospinal tract for monitoring axonal responses to spinal cord injury.
The rodent corticospinal tract (CST) has been used extensively to investigate regeneration and remodeling of central axons after injury. CST axons are currently visualized after injection of tracer dye, which is invasive, incomplete and prone to variation, and often does not show functionally crucial but numerically minor tract components. Here, we characterize transgenic mice in which CST fibers are specifically and completely labeled by yellow fluorescent protein (YFP). Using these CST-YFP mice, we show that minor CST components are responsible for most monosynaptic contacts onto motoneurons. Lesions of the main dorsal CST lead to extension of new collaterals, some of them originating from large, heavily myelinated axons within the minor dorsolateral and ventral CST components. Some of these new collaterals form additional direct synapses onto motoneurons. We propose that CST-YFP mice will be useful for evaluating strategies designed to maximize such remodeling and to promote regeneration.
Bareyre
Florence M
FM
Department of Molecular and Cellular Biology, Harvard University, Sherman Fairchild Building, Room 143, 7 Divinity Avenue, Cambridge, Massachusetts 02138, USA.
Kerschensteiner
Martin
M
Misgeld
Thomas
T
Sanes
Joshua R
JR
D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000502:physiology*; D001426:Bacterial Proteins; D008164:Luminescent Proteins; D051379:Mice; D009416:Nerve Regeneration / Q000502:physiology*; D011712:Pyramidal Tracts / Q000166:cytology* / Q000196:embryology; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013194:Staining and Labeling / Q000379:methods*
D001426:Bacterial Proteins; D008164:Luminescent Proteins; C054562:yellow fluorescent protein, Bacteria