title: De novo GMP synthesis is required for axon guidance in Drosophila.
abstract: Guanine nucleotides are key players in mediating growth-cone signaling during neural development. The supply of cellular guanine nucleotides in animals can be achieved via the de novo synthesis and salvage pathways. The de novo synthesis of guanine nucleotides is required for lymphocyte proliferation in animals. Whether the de novo synthesis pathway is essential for any other cellular processes, however, remains unknown. In a search for genes required for the establishment of neuronal connectivity in the fly visual system, we identify the burgundy (bur) gene as an essential player in photoreceptor axon guidance. The bur gene encodes the only GMP synthetase in Drosophila that catalyzes the final reaction of de novo GMP synthesis. Loss of bur causes severe defects in axonal fasciculation, retinotopy, and growth-cone morphology, but does not affect photoreceptor differentiation or retinal patterning. Similar defects were observed when the raspberry (ras) gene, encoding for inosine monophosphate dehydrogenase catalyzing the IMP-to-XMP conversion in GMP de novo synthesis, was mutated. Our study thus provides the first in vivo evidence to support an essential and specific role for de novo synthesis of guanine nucleotides in axon guidance.
authors.affiliation: McGill Centre for Research in Neuroscience and Department of Neurology and Neurosurgery, McGill University Health Centre, Montreal, Quebec H3G 1A4, Canada.
authors.forename: Hong
authors.initials: H
authors.lastname: Long
authors.forename: Scott
authors.initials: S
authors.lastname: Cameron
authors.forename: Li
authors.initials: L
authors.lastname: Yu
authors.forename: Yong
authors.initials: Y
authors.lastname: Rao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D019521:Body Patterning / Q000235:genetics / Q000502:physiology; D019731:Carbon-Nitrogen Ligases / Q000235:genetics / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics; D004330:Drosophila / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D019143:Evolution, Molecular; D006157:Guanosine Monophosphate / Q000096:biosynthesis*; D007814:Larva / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009899:Optic Lobe, Nonmammalian / Q000201:enzymology / Q000254:growth & development; D017956:Photoreceptor Cells, Invertebrate / Q000201:enzymology / Q000378:metabolism / Q000502:physiology; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000502:physiology
chemical_list: D006157:Guanosine Monophosphate; D020744:rac GTP-Binding Proteins; D019731:Carbon-Nitrogen Ligases; C020828:GMP synthase (glutamine-hydrolyzing)