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Published December 1, 1994 | Published
Journal Article Open

A Drosophila Receptor Tyrosine Phosphatase Expressed in the Embryonic CNS and Larval Optic Lobes Is a Member of the Set of Proteins Bearing the "HRP" Carbohydrate Epitope


Recent studies have defined several cell surface glycoproteins expressed in the developing nervous system of insect embryos that may be involved in axon outgrowth and guidance processes. These glycoproteins include the fasciclins and a group of receptor-linked protein tyrosine phosphatases (R-PTPs). In embryos, the fasciclins are localized to axonal subsets, while the R-PTPs appear to be expressed on most or all CNS axons. To identify other neuronal cell surface glycoproteins in the Drosophila embryo, we have taken a biochemical approach. This is based on the observation that antisera against horseradish peroxidase (HRP) recognize a carbohydrate epitope that is selectively expressed in the insect nervous system. A large number of neuronal glycoproteins (denoted "HRP proteins") apparently bear the HRP carbohydrate epitope. We have used polyclonal anti-HRP antibodies to purify these proteins from Drosophila embryos, and have obtained protein sequences from seven HRP protein bands. These data define three major HRP proteins as neurotactin, fasciclin I, and an R-PTP, DPTP69D. Western blotting data suggest that fasciclin II, neuroglian, DPTP10D, and DPTP99A are also HRP proteins. We show that DPTP69D, like the previously characterized R-PTPs, is localized to CNS axons in the embryo. In third instar larvae, DPTP69D expression is restricted to subsets of neuronal processes in the brain, ventral nerve cord, and eye disk. In the optic lobes, DPTP69D is localized to the neuropils of the lamina and medulla, and to an array of parallel thick bundles that may be the transmedullary fibers of the developing lobula complex.

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© 1994 Society for Neuroscience. Beginning six months after publication the Work will be made freely available to the public on SfN's website to copy, distribute, or display under a Creative Commons Attribution 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/). Received Feb. 25, 1994; revised May 19, 1994; accepted May 26, 1994. We thank David Teplow (Caltech Microchemical Facility) and Hediye Erdjument-Bromage and Paul Tempst (Sloan-Kettering Memorial Cancer Center, New York) for protein sequencing. We thank Susan Ou and the Caltech monoclonal antibody facility for performing MAb fusions. We also thank Ron Davis and Kyung-An Han (Baylor University) for the M60 enhancer trap line and for helpful discussions, Suma Datta, Konrad Zinsmaier, Doris Kretzschmar, Simona Tix, Paul Garrity, and Howard Lipshitz for discussions concerning the DPTP69D optic lobe expression pattern, Mark Seeger for discussions on PTP genetics, Rosalind Young for help with sectioning, Nancy Bonini for the larval brain immunohistochemistry protocol, Barry Condron for help with confocal microscopy, Michel Piovant for the FA4 MAb, Corey Goodman for the ID4 MAb, and Shin-Shay Tian for performing the in situ hybridization. C.J.D. was supported by a postdoctoral fellowship from the American Cancer Society. This work was supported by a grant (NS28182) from the NIH to K.Z., as well as by a Pew Scholars Award, a McKnight Scholars Award, and a Basil O'Connor Starter Scholars Award (5-816) from the March of Dimes Birth Defects Foundation.

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