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Published May 1997 | Published
Journal Article Open

Competition and cooperation among receptor tyrosine phosphatases control motoneuron growth cone guidance in Drosophila


The neural receptor tyrosine phosphatases DPTP69D, DPTP99A and DLAR are involved in motor axon guidance in the Drosophila embryo. Here we analyze the requirements for these three phosphatases in growth cone guidance decisions along the ISN and SNb motor pathways. Any one of the three suffices for the progression of ISN pioneer growth cones beyond their first intermediate target in the dorsal muscle field. DLAR or DPTP69D can facilitate outgrowth beyond a second intermediate target, and DLAR is uniquely required for formation of a normal terminal arbor. A different pattern of partial redundancy among the three phosphatases is observed for the SNb pathway. Any one of the three suffices to allow SNb axons to leave the common ISN pathway at the exit junction. When DLAR is not expressed, however, SNb axons sometimes bypass their ventrolateral muscle targets after leaving the common pathway, instead growing out as a separate bundle adjacent to the ISN. This abnormal guidance decision can be completely suppressed by also removing DPTP99A, suggesting that DLAR turns off or counteracts a DPTP99A signal that favors the bypass axon trajectory. Our results show that the relationships among the tyrosine phosphatases are complex and dependent on cellular context. At growth cone choice points along one nerve, two phosphatases cooperate, while along another nerve these same phosphatases can act in opposition to one another.

Additional Information

© 1997 The Company of Biologists Limited. Accepted 24 February 1997. We thank Siegfried Roth for the anti-Twist antiserum, Corey Goodman for mAb 1D4, Bill Chia for Df(3R)KE, and David Van Vactor and the members of our laboratories for helpful discussions and comments on the manuscript. This work was supported by National Institutes of Health grants NS28182 to K. Z. and GM-53415 to H. S.

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