Abstract
L1- and NCAM-type cell adhesion molecules represent distinct protein families that function as specific receptors for different axon guidance cues. However, both L1 and NCAM proteins promote axonal growth by inducing neuronal tyrosine kinase activity and are coexpressed in subsets of axon tracts in arthropods and vertebrates. We have studied the functional requirements for the Drosophila L1- and NCAM-type proteins, Neuroglian (Nrg) and Fasciclin II (FasII), during postembryonic sensory axon guidance. The rescue of the Neuroglian loss-of-function (LOF) phenotype by transgenically expressed L1- and NCAM-type proteins demonstrates a functional interchangeability between these proteins in Drosophila photoreceptor pioneer axons, where both proteins are normally coexpressed. In contrast, the ectopic expression of Fasciclin II in mechanosensory neurons causes a strong enhancement of the axonal misguidance phenotype. Moreover, our findings demonstrate that this functionally redundant specificity to mediate axon guidance has been conserved in their vertebrate homologs, L1-CAM and NCAM.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Cell Adhesion Molecules, Neuronal / genetics*
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Cell Adhesion Molecules, Neuronal / metabolism
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Cell Communication / genetics
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Drosophila / embryology*
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Drosophila / genetics
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Drosophila / metabolism
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Drosophila Proteins
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Eye / cytology
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Eye / embryology
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Eye / metabolism
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Gene Expression Regulation, Developmental / genetics
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Growth Cones / metabolism*
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Growth Cones / ultrastructure
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Mechanoreceptors / cytology
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Mechanoreceptors / embryology
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Mechanoreceptors / metabolism
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Nervous System / cytology
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Nervous System / embryology*
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Nervous System / metabolism
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Neural Cell Adhesion Molecule L1 / genetics
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Neural Cell Adhesion Molecule L1 / metabolism
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Neural Cell Adhesion Molecules / genetics
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Neural Cell Adhesion Molecules / metabolism
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Neurons, Afferent / cytology
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Neurons, Afferent / metabolism*
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Phenotype
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Photoreceptor Cells, Invertebrate / cytology
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Photoreceptor Cells, Invertebrate / embryology
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Photoreceptor Cells, Invertebrate / metabolism
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Transgenes / genetics
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Wings, Animal / cytology
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Wings, Animal / embryology
Substances
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Cell Adhesion Molecules, Neuronal
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Drosophila Proteins
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Neural Cell Adhesion Molecule L1
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Neural Cell Adhesion Molecules
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fasciclin II
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Nrg protein, Drosophila