Lb. Andersen et Dj. Schreyer, Constitutive expression of GAP-43 correlates with rapid, but not slow regrowth of injured dorsal root axons in the adult rat, EXP NEUROL, 155(2), 1999, pp. 157-164
It has been postulated that the neuronal growth associated protein GAP-43 p
lays an essential role in axon elongation. Although termination of developm
ental axon growth is generally accompanied by a decline in expression of GA
P-43, a subpopulation of dorsal root ganglion (DRG) neurons retains constit
utive expression of GAP-43 throughout adulthood. Peripheral nerve regenerat
ion occurring subsequent to injury of the peripheral axon branches of adult
DRG neurons is accompanied by renewed elevation of GAP-43 expression. Lesi
ons of DRG central axon branches in the dorsal roots are also followed by S
ome regenerative growth, but little or no increase in GAP-43 expression abo
ve the constitutive level is observed. To determine whether dorsal root axo
n regeneration occurs only from neurons which constitutively express GAP-43
, we have used retrograde fluorescent labeling to identify those DRG neuron
s which extend axons beyond a crush lesion of the dorsal root. Only GAP-43
immunoreactive neurons supported axon regrowth of 7 mm or greater within th
e first week. At later times, axon regrowth is seen to occur from neurons b
oth with and without GAP-43 immunoreactivity. We conclude that regeneration
of injured axons within the dorsal root is not absolutely dependent on the
presence of GAP-43, but that expression of GAP-43 is correlated with a cap
acity for rapid growth. (c) 1999 Academic Press.