Growth cone steering by receptor tyrosine phosphatase delta defines a distinct class of guidance cue

Receptor-type tyrosine phosphatases (RPTPs) are involved in pathfinding dec isions by elongating axons, but how they function in these decisions remain s unclear. A vertebrate RPTP, PTP-delta, is a neurite-promoting homophilic adhesion molecule; here we demonstrate chemoattraction of CNS growth cones by a locally applied gradient of soluble PTP-delta. The attractive effect o f PTP-delta was abolished by inhibition of tyrosine phosphatase activity, b ut in contrast to other guidance proteins was unaffected by inhibition of c yclic nucleotide activities. Gradients of PTP-delta or of laminin-l also pr omoted increases in the speed of growth cone migration, but laminin-l did n ot steer growth cones. Our results indicate that PTP-delta is a chemoattrac tant for vertebrate CNS neurons in vitro and suggest that it represents a d istinct class of guidance protein from those previously defined. Further, o ur data indicate that growth cone attraction is mechanistically distinct fr om increases in the speed of growth cone movement.