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

Receptor-type tyrosine phosphatases (RPTPs) are involved in pathfinding decisions by elongating axons, but how they function in these decisions remains 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 of PTP-delta was abolished by inhibition of tyrosine phosphatase activity, but in contrast to other guidance proteins was unaffected by inhibition of cyclic nucleotide activities. Gradients of PTP-delta or of laminin-1 also promoted increases in the speed of growth cone migration, but laminin-1 did not steer growth cones. Our results indicate that PTP-delta is a chemoattractant for vertebrate CNS neurons in vitro and suggest that it represents a distinct class of guidance protein from those previously defined. Further, our data indicate that growth cone attraction is mechanistically distinct from increases in the speed of growth cone movement.