Regulation of CNS and motor axon guidance in Drosophila by the receptor tyrosine phosphatase DPTP52F

Receptor-linked protein tyrosine phosphatases (RPTPs) regulate axon guidanc e and synaptogenesis in Drosophila embryos and larvae. We describe DPTP52F, the sixth RPTP to be discovered in Drosophila. Our genomic analysis indica tes that there are likely to be no additional RPTPs encoded in the fly geno me. Five of the six Drosophila RPTPs have C. elegans counterparts, and thre e of the six are also orthologous to human, RPTP subfamilies. DPTP52F, howe ver, has no clear orthologs in other organisms. The DPTP52F extracellular d omain contains five fibronectin type III repeats and it has a single phosph atase domain. DPTP52F is selectively expressed in the CNS of late embryos, as are DPTP10D, DLAR, DPTP69D and DPTP99A. To define developmental roles of DPTP52F, we used RNA interference (RNAi)-induced phenotypes as a guide to identify Ptp52F alleles among a collection of EMS-induced lethal mutations. Ptp52F single mutant embryos have axon guidance phenotypes that affect CNS longitudinal tracts. This phenotype is suppressed in Dlar Ptp52F double mu tants, indicating that DPTP52F and DLAR interact competitively in regulatin g CNS axon guidance decisions. Ptp52F single mutations also cause motor axo n phenotypes that selectively affect the SNa nerve. DPTP52F, DPTP10D and DP TP69D have partially redundant roles in regulation of guidance decisions ma de by axons within the ISN and ISNb motor nerves.