Three receptor-linked protein-tyrosine phosphatases are selectively expressed on central nervous system axons in the Drosophila embryo

We describe the isolation of seven different protein-tyrosine phosphatase (PTPase) cDNAs from Drosophila embryos, three of which are primarily expressed in the central nervous system (CNS). The CNS-specific PTPases include the previously sequenced DLAR, as well as two novel PTPases (denoted DPTP_(10D) and DPTP_(99A)), which have extracellular domains consisting of multiple fibronectin type III repeats. Each of the Drosophila sequences is most closely related to a different human PTPase. The three PTPase mRNAs are expressed in different patterns of cells in the ventral nerve cord, and all three proteins are restricted to axons. DLAR and DPTP_(99A) are apparently expressed on most or all axons, while DPTP_(10D) is primarily localized to the anterior commissure and its junctions with the longitudinal tracts