title: Dynamic expression of the cell adhesion molecule fasciclin I during embryonic development in Drosophila.
abstract: A number of different cell surface glycoproteins expressed in the central nervous system (CNS) have been identified in insects and shown to mediate cell adhesion in tissue culture systems. The fasciclin I protein is expressed on a subset of CNS axon pathways in both grasshopper and Drosophila. It consists of four homologous 150-amino acid domains which are unrelated to other sequences in the current databases, and is tethered to the cell surface by a glycosyl-phosphatidylinositol linkage. In this paper we examine in detail the expression of fasciclin I mRNA and protein during Drosophila embryonic development. We find that fasciclin I is expressed in several distinct patterns at different stages of development. In blastoderm embryos it is briefly localized in a graded pattern. During the germ band extended period its expression evolves through two distinct phases. Fasciclin I mRNA and protein are initially localized in a 14-stripe pattern which corresponds to segmentally repeated patches of neuroepithelial cells and neuroblasts. Expression then becomes confined to CNS and peripheral sensory (PNS) neurons. Fasciclin I is expressed on all PNS neurons, and this expression is stably maintained for several hours. In the CNS, fasciclin I is initially expressed on all commissural axons, but then becomes restricted to specific axon bundles. The early commissural expression pattern is not observed in grasshopper embryos, but the later bundle-specific pattern is very similar to that seen in grasshopper. The existence of an initial phase of expression on all commissural bundles helps to explain the loss-of-commissures phenotype of embryos lacking expression of both fasciclin I and of the D-abl tyrosine kinase. Fasciclin I is also expressed in several nonneural tissues in the embryo.
authors.affiliation: Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley 94720.
authors.forename: L
authors.initials: L
authors.lastname: McAllister
authors.forename: C S
authors.initials: CS
authors.lastname: Goodman
authors.forename: K
authors.initials: K
authors.lastname: Zinn
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D015816:Cell Adhesion Molecules, Neuronal / Q000235:genetics*; D002490:Central Nervous System / Q000196:embryology*; D004330:Drosophila / Q000196:embryology* / Q000235:genetics; D015870:Gene Expression / Q000502:physiology*; D006110:Grasshoppers / Q000196:embryology / Q000502:physiology; D007150:Immunohistochemistry; D009024:Morphogenesis / Q000235:genetics; D010525:Peripheral Nerves / Q000196:embryology / Q000502:physiology
chemical_list: D015816:Cell Adhesion Molecules, Neuronal; C051641:fasciclin I