title: Synaptic roles for phosphomannomutase type 2 in a new Drosophila congenital disorder of glycosylation disease model.
abstract: Congenital disorders of glycosylation (CDGs) constitute a rapidly growing family of human diseases resulting from heritable mutations in genes driving the production and modification of glycoproteins. The resulting symptomatic hypoglycosylation causes multisystemic defects that include severe neurological impairments, revealing a particularly critical requirement for tightly regulated glycosylation in the nervous system. The most common CDG, CDG-Ia (PMM2-CDG), arises from phosphomannomutase type 2 (PMM2) mutations. Here, we report the generation and characterization of the first Drosophila CDG-Ia model. CRISPR-generated pmm2-null Drosophila mutants display severely disrupted glycosylation and early lethality, whereas RNAi-targeted knockdown of neuronal PMM2 results in a strong shift in the abundance of pauci-mannose glycan, progressive incoordination and later lethality, closely paralleling human CDG-Ia symptoms of shortened lifespan, movement impairments and defective neural development. Analyses of the well-characterized Drosophila neuromuscular junction (NMJ) reveal synaptic glycosylation loss accompanied by defects in both structural architecture and functional neurotransmission. NMJ synaptogenesis is driven by intercellular signals that traverse an extracellular synaptomatrix and are co-regulated by glycosylation and matrix metalloproteinases (MMPs). Specifically, trans-synaptic signaling by the Wnt protein Wingless (Wg) depends on the heparan sulfate proteoglycan (HSPG) co-receptor Dally-like protein (Dlp), which is regulated by synaptic MMP activity. Loss of synaptic MMP2, Wg ligand, Dlp co-receptor and downstream trans-synaptic signaling occurs with PMM2 knockdown. Taken together, this Drosophila CDG disease model provides a new avenue for the dissection of cellular and molecular mechanisms underlying neurological impairments and is a means by which to discover and test novel therapeutic treatment strategies.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Parkinson
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA 30602, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Dookwah
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: Mary Lynn
authors.initials: ML
authors.lastname: Dear
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA.
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Gatto
authors.affiliation: Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602, USA.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Aoki
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA 30602, USA Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Tiemeyer
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235, USA Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37235, USA kendal.broadie@vanderbilt.edu.
authors.forename: Kendal
authors.initials: K
authors.lastname: Broadie
mesh_terms: D000818:Animals; D018981:Congenital Disorders of Glycosylation / Q000201:enzymology* / Q000473:pathology* / Q000503:physiopathology; D004195:Disease Models, Animal; D015536:Down-Regulation; D004330:Drosophila / Q000201:enzymology*; D029721:Drosophila Proteins / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism; D006031:Glycosylation; D008136:Longevity; D009068:Movement; D009469:Neuromuscular Junction / Q000378:metabolism; D009844:Oligosaccharides / Q000378:metabolism; D017875:Phosphotransferases (Phosphomutases) / Q000172:deficiency* / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D011187:Posture; D017729:Presynaptic Terminals / Q000378:metabolism; D015398:Signal Transduction; D013569:Synapses / Q000201:enzymology*; D009435:Synaptic Transmission
chemical_list: D029721:Drosophila Proteins; D006023:Glycoproteins; D009844:Oligosaccharides; D011134:Polysaccharides; D017875:Phosphotransferases (Phosphomutases); C000625348:PMM2 protein, Drosophila; C052799:phosphomannomutase
keywords: Matrix metalloproteinase; Neuromuscular junction; Neurotransmission; Synapse; Synaptomatrix; Trans-synaptic signaling; Wnt