HYPERINNERVATION OF NEUROMUSCULAR-JUNCTIONS CAUSED BY GDNF OVEREXPRESSION IN MUSCLE

Overexpression of glial cell line-derived neurotrophic factor (GDNF) b y muscle greatly increased the number of motor axons innervating neuro muscular junctions in neonatal mice. The extent of hyperinnervation co rrelated with the amount of GDNF expressed in four transgenic lines. O verexpression of GDNF by glia and overexpression of neurotrophin-3 and neurotrophin-4 in muscle did not cause hyperinnervation. Thus, increa sed amounts of GDNF in postsynaptic target cells can regulate the numb er of innervating axons.