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von Saucken VE, Windner SE, Baylies MK. Postsynaptic BMP signaling regulates myonuclear properties in Drosophila larval muscles. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.10.588944. [PMID: 38645063 PMCID: PMC11030338 DOI: 10.1101/2024.04.10.588944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The syncytial mammalian muscle fiber contains a heterogeneous population of (myo)nuclei. At the neuromuscular junction (NMJ), myonuclei have specialized positioning and gene expression. However, it remains unclear how myonuclei are recruited and what regulates myonuclear output at the NMJ. Here, we identify specific properties of myonuclei located near the Drosophila larval NMJ. These synaptic myonuclei have increased size in relation to their surrounding cytoplasmic domain (scaling), increased DNA content (ploidy), and increased levels of transcription factor pMad, a readout for BMP signaling activity. Our genetic manipulations show local BMP signaling affects muscle size, nuclear size, ploidy, and NMJ size and function. In support, RNA sequencing analysis reveals that pMad regulates genes involved in muscle growth, ploidy (i.e., E2f1), and neurotransmission. Our data suggest that muscle BMP signaling instructs synaptic myonuclear output that then positively shapes the NMJ synapse. This study deepens our understanding of how myonuclear heterogeneity supports local signaling demands to fine tune cellular function and NMJ activity.
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Affiliation(s)
- Victoria E. von Saucken
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065 USA
- Weill Cornell-Rockefeller-Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY 10065 USA
- Biochemistry, Cell & Developmental Biology, and Molecular Biology (BCMB) Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065 USA
| | - Stefanie E. Windner
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065 USA
| | - Mary K. Baylies
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065 USA
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2
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Vicidomini R, Serpe M. Local BMP signaling: A sensor for synaptic activity that balances synapse growth and function. Curr Top Dev Biol 2022; 150:211-254. [PMID: 35817503 PMCID: PMC11102767 DOI: 10.1016/bs.ctdb.2022.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Synapse development is coordinated by intercellular communication between the pre- and postsynaptic compartments, and by neuronal activity itself. In flies as in vertebrates, neuronal activity induces input-specific changes in the synaptic strength so that the entire circuit maintains stable function in the face of many challenges, including changes in synapse number and strength. But how do neurons sense synapse activity? In several studies carried out using the Drosophila neuromuscular junction (NMJ), we demonstrated that local BMP signaling provides an exquisite sensor for synapse activity. Here we review the main features of this exquisite sensor and discuss its functioning beyond monitoring the synapse activity but rather as a key controller that operates in coordination with other BMP signaling pathways to balance synapse growth, maturation and function.
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Affiliation(s)
- Rosario Vicidomini
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States
| | - Mihaela Serpe
- Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States.
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3
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Sidisky JM, Weaver D, Hussain S, Okumus M, Caratenuto R, Babcock D. Mayday sustains trans-synaptic BMP signaling required for synaptic maintenance with age. eLife 2021; 10:e54932. [PMID: 33667157 PMCID: PMC7935490 DOI: 10.7554/elife.54932] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 02/23/2021] [Indexed: 01/12/2023] Open
Abstract
Maintaining synaptic structure and function over time is vital for overall nervous system function and survival. The processes that underly synaptic development are well understood. However, the mechanisms responsible for sustaining synapses throughout the lifespan of an organism are poorly understood. Here, we demonstrate that a previously uncharacterized gene, CG31475, regulates synaptic maintenance in adult Drosophila NMJs. We named CG31475 mayday due to the progressive loss of flight ability and synapse architecture with age. Mayday is functionally homologous to the human protein Cab45, which sorts secretory cargo from the Trans Golgi Network (TGN). We find that Mayday is required to maintain trans-synaptic BMP signaling at adult NMJs in order to sustain proper synaptic structure and function. Finally, we show that mutations in mayday result in the loss of both presynaptic motor neurons as well as postsynaptic muscles, highlighting the importance of maintaining synaptic integrity for cell viability.
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Affiliation(s)
- Jessica M Sidisky
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Daniel Weaver
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Sarrah Hussain
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Meryem Okumus
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Russell Caratenuto
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Daniel Babcock
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
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4
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Abdel Mouti M, Pauklin S. TGFB1/INHBA Homodimer/Nodal-SMAD2/3 Signaling Network: A Pivotal Molecular Target in PDAC Treatment. Mol Ther 2021; 29:920-936. [PMID: 33429081 PMCID: PMC7934636 DOI: 10.1016/j.ymthe.2021.01.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/17/2020] [Accepted: 01/02/2021] [Indexed: 02/06/2023] Open
Abstract
Pancreatic cancer remains a grueling disease that is projected to become the second-deadliest cancer in the next decade. Standard treatment of pancreatic cancer is chemotherapy, which mainly targets the differentiated population of tumor cells; however, it paradoxically sets the roots of tumor relapse by the selective enrichment of intrinsically chemoresistant pancreatic cancer stem cells that are equipped with an indefinite capacity for self-renewal and differentiation, resulting in tumor regeneration and an overall anemic response to chemotherapy. Crosstalk between pancreatic tumor cells and the surrounding stromal microenvironment is also involved in the development of chemoresistance by creating a supportive niche, which enhances the stemness features and tumorigenicity of pancreatic cancer cells. In addition, the desmoplastic nature of the tumor-associated stroma acts as a physical barrier, which limits the intratumoral delivery of chemotherapeutics. In this review, we mainly focus on the transforming growth factor beta 1 (TGFB1)/inhibin subunit beta A (INHBA) homodimer/Nodal-SMAD2/3 signaling network in pancreatic cancer as a pivotal central node that regulates multiple key mechanisms involved in the development of chemoresistance, including enhancement of the stem cell-like properties and tumorigenicity of pancreatic cancer cells, mediating cooperative interactions between pancreatic cancer cells and the surrounding stroma, as well as regulating the deposition of extracellular matrix proteins within the tumor microenvironment.
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Affiliation(s)
- Mai Abdel Mouti
- Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Headington, University of Oxford, Oxford OX3 7LD, UK
| | - Siim Pauklin
- Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Headington, University of Oxford, Oxford OX3 7LD, UK.
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5
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Nguyen TH, Han TH, Newfeld SJ, Serpe M. Selective Disruption of Synaptic BMP Signaling by a Smad Mutation Adjacent to the Highly Conserved H2 Helix. Genetics 2020; 216:159-175. [PMID: 32737119 PMCID: PMC7463279 DOI: 10.1534/genetics.120.303484] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 07/16/2020] [Indexed: 01/08/2023] Open
Abstract
Bone morphogenetic proteins (BMPs) shape normal development and function via canonical and noncanonical signaling pathways. BMPs initiate canonical signaling by binding to transmembrane receptors that phosphorylate Smad proteins and induce their translocation into the nucleus and regulation of target genes. Phosphorylated Smads also accumulate at cellular junctions, but this noncanonical, local BMP signaling modality remains less defined. We have recently reported that phosphorylated Smad (pMad in Drosophila) accumulates at synaptic junctions in protein complexes with genetically distinct composition and regulation. Here, we examined a wide collection of DrosophilaMad alleles and searched for molecular features relevant to pMad accumulation at synaptic junctions. We found that strong Mad alleles generally disrupt both synaptic and nuclear pMad, whereas moderate Mad alleles have a wider range of phenotypes and can selectively impact different BMP signaling pathways. Interestingly, regulatory Mad mutations reveal that synaptic pMad appears to be more sensitive to a net reduction in Mad levels than nuclear pMad. Importantly, a previously uncharacterized allele, Mad8 , showed markedly reduced synaptic pMad but only moderately diminished nuclear pMad. The postsynaptic composition and electrophysiological properties of Mad8 neuromuscular junctions (NMJs) were also altered. Using biochemical approaches, we examined how a single point mutation in Mad8 could influence the Mad-receptor interface and identified a key motif, the H2 helix. Our study highlights the biological relevance of Smad-dependent, synaptic BMP signaling and uncovers a highly conserved structural feature of Smads, critical for normal development and function.
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Affiliation(s)
- Tho Huu Nguyen
- Section on Cellular Communication, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Tae Hee Han
- Section on Cellular Communication, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
| | - Stuart J Newfeld
- School of Life Sciences, Arizona State University, Tempe, Arizona 85287-4501
| | - Mihaela Serpe
- Section on Cellular Communication, Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
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Brown JR, Phongthachit C, Sulkowski MJ. Immunofluorescence and image analysis pipeline for Drosophila motor neurons. Biol Methods Protoc 2019; 4:bpz010. [PMID: 31403085 PMCID: PMC6676502 DOI: 10.1093/biomethods/bpz010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 07/03/2019] [Accepted: 07/09/2019] [Indexed: 11/23/2022] Open
Abstract
The neuromuscular junction (NMJ) of larval Drosophila is widely used as a genetic model for basic neuroscience research. The presynaptic side of the NMJ is formed by axon terminals of motor neurons, the soma of which reside in the ventral ganglion of the central nervous system (CNS). Here we describe a streamlined protocol for dissection and immunostaining of the Drosophila CNS and NMJ that allows processing of multiple genotypes within a single staining tube. We also present a computer script called Automated Image Analysis with Background Subtraction which facilitates identification of motor nuclei, quantification of pixel intensity, and background subtraction. Together, these techniques provide a pipeline for neuroscientists to compare levels of different biomolecules in motor nuclei. We conclude that these methods should be adaptable to a variety of different cell and tissue types for the improvement of efficiency, reproducibility, and throughput during data quantification.
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Affiliation(s)
- Jeremy R Brown
- Biology Department, Southern Arkansas University, Magnolia, AR, USA
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO, USA
| | | | - Mikolaj J Sulkowski
- Biology Department, Southern Connecticut State University, New Haven, CT, USA
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7
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Astrocytes and the TGF-β1 Pathway in the Healthy and Diseased Brain: a Double-Edged Sword. Mol Neurobiol 2018; 56:4653-4679. [DOI: 10.1007/s12035-018-1396-y] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 10/14/2018] [Indexed: 12/14/2022]
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8
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Dear ML, Shilts J, Broadie K. Neuronal activity drives FMRP- and HSPG-dependent matrix metalloproteinase function required for rapid synaptogenesis. Sci Signal 2017; 10:eaan3181. [PMID: 29114039 PMCID: PMC5743058 DOI: 10.1126/scisignal.aan3181] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Matrix metalloproteinase (MMP) functions modulate synapse formation and activity-dependent plasticity. Aberrant MMP activity is implicated in fragile X syndrome (FXS), a disease caused by the loss of the RNA-binding protein FMRP and characterized by neurological dysfunction and intellectual disability. Gene expression studies in Drosophila suggest that Mmps cooperate with the heparan sulfate proteoglycan (HSPG) glypican co-receptor Dally-like protein (Dlp) to restrict trans-synaptic Wnt signaling and that synaptogenic defects in the fly model of FXS are alleviated by either inhibition of Mmp or genetic reduction of Dlp. We used the Drosophila neuromuscular junction (NMJ) glutamatergic synapse to test activity-dependent Dlp and Mmp intersections in the context of FXS. We found that rapid, activity-dependent synaptic bouton formation depended on secreted Mmp1. Acute neuronal stimulation reduced the abundance of Mmp2 but increased that of both Mmp1 and Dlp, as well as enhanced the colocalization of Dlp and Mmp1 at the synapse. Dlp function promoted Mmp1 abundance, localization, and proteolytic activity around synapses. Dlp glycosaminoglycan (GAG) chains mediated this functional interaction with Mmp1. In the FXS fly model, activity-dependent increases in Mmp1 abundance and activity were lost but were restored by reducing the amount of synaptic Dlp. The data suggest that neuronal activity-induced, HSPG-dependent Mmp regulation drives activity-dependent synaptogenesis and that this is impaired in FXS. Thus, exploring this mechanism further may reveal therapeutic targets that have the potential to restore synaptogenesis in FXS patients.
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Affiliation(s)
- Mary L Dear
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Jarrod Shilts
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA
| | - Kendal Broadie
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA.
- Department of Cell and Developmental Biology, Vanderbilt University and Medical School, Nashville, TN 37232, USA
- Vanderbilt Brain Institute, Vanderbilt University and Medical School, Nashville, TN 37232, USA
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9
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Regulatory Mechanisms of Metamorphic Neuronal Remodeling Revealed Through a Genome-Wide Modifier Screen in Drosophila melanogaster. Genetics 2017; 206:1429-1443. [PMID: 28476867 PMCID: PMC5500141 DOI: 10.1534/genetics.117.200378] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 04/28/2017] [Indexed: 02/01/2023] Open
Abstract
During development, neuronal remodeling shapes neuronal connections to establish fully mature and functional nervous systems. Our previous studies have shown that the RNA-binding factor alan shepard (shep) is an important regulator of neuronal remodeling during metamorphosis in Drosophila melanogaster, and loss of shep leads to smaller soma size and fewer neurites in a stage-dependent manner. To shed light on the mechanisms by which shep regulates neuronal remodeling, we conducted a genetic modifier screen for suppressors of shep-dependent wing expansion defects and cellular morphological defects in a set of peptidergic neurons, the bursicon neurons, that promote posteclosion wing expansion. Out of 702 screened deficiencies that covered 86% of euchromatic genes, we isolated 24 deficiencies as candidate suppressors, and 12 of them at least partially suppressed morphological defects in shep mutant bursicon neurons. With RNA interference and mutant alleles of individual genes, we identified Daughters against dpp (Dad) and Olig family (Oli) as shep suppressor genes, and both of them restored the adult cellular morphology of shep-depleted bursicon neurons. Dad encodes an inhibitory Smad protein that inhibits bone morphogenetic protein (BMP) signaling, raising the possibility that shep interacted with BMP signaling through antagonism of Dad. By manipulating expression of the BMP receptor tkv, we found that activated BMP signaling was sufficient to rescue loss-of-shep phenotypes. These findings reveal mechanisms of shep regulation during neuronal development, and they highlight a novel genetic shep interaction with the BMP signaling pathway that controls morphogenesis in mature, terminally differentiated neurons during metamorphosis.
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10
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An organotypic slice culture to study the formation of calyx of Held synapses in-vitro. PLoS One 2017; 12:e0175964. [PMID: 28419135 PMCID: PMC5395213 DOI: 10.1371/journal.pone.0175964] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 04/03/2017] [Indexed: 12/29/2022] Open
Abstract
The calyx of Held, a large axo-somatic relay synapse containing hundreds of presynaptic active zones, is possibly the largest nerve terminal in the mammalian CNS. Studying its initial growth in-vitro might provide insights into the specification of synaptic connection size in the developing brain. However, attempts to maintain calyces of Held in organotypic cultures have not been fruitful in past studies. Here, we describe an organotypic slice culture method in which calyces of Held form in-vitro. We made coronal brainstem slices with an optimized slice angle using newborn mice in which calyces have not yet formed; the presynaptic bushy cells were genetically labeled using the Math5 promoter. After six to nine days of culturing, we readily observed large Math5—positive nerve terminals in the medial nucleus of the trapezoid body (MNTB), but not in the neighboring lateral superior olive nucleus (LSO). These calyx—like synapses expressed the Ca2+- sensor Synaptotagmin-2 (Syt-2) and the Ca2+ binding protein Parvalbumin (PV), two markers of developing calyces of Held in vivo. Application of the BMP inhibitor LDN-193189 significantly inhibited the growth of calyx synapses, demonstrating the feasibility of long-term pharmacological manipulation using this organotypic culture method. These experiments provide a method for organotypic culturing of calyces of Held, and show that the formation of calyx—like synapses onto MNTB neurons can be preserved in-vitro. Furthermore, our study adds pharmacological evidence for a role of BMP-signaling in the formation of large calyx of Held synapses.
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Pathogenic Huntington Alters BMP Signaling and Synaptic Growth through Local Disruptions of Endosomal Compartments. J Neurosci 2017; 37:3425-3439. [PMID: 28235896 DOI: 10.1523/jneurosci.2752-16.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/07/2017] [Accepted: 02/13/2017] [Indexed: 01/05/2023] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by expansion of a polyglutamine (polyQ) stretch within the Huntingtin (Htt) protein. Pathogenic Htt disrupts multiple neuronal processes, including gene expression, axonal trafficking, proteasome and mitochondrial activity, and intracellular vesicle trafficking. However, the primary pathogenic mechanism and subcellular site of action for mutant Htt are still unclear. Using a Drosophila HD model, we found that pathogenic Htt expression leads to a profound overgrowth of synaptic connections that correlates directly with the levels of Htt at nerve terminals. Branches of the same nerve containing different levels of Htt show distinct phenotypes, indicating that Htt acts locally to disrupt synaptic growth. The effects of pathogenic Htt on synaptic growth arise from defective synaptic endosomal trafficking, leading to expansion of a recycling endosomal signaling compartment containing Sorting Nexin 16 and a reduction in late endosomes containing Rab11. The disruption of endosomal compartments leads to elevated BMP signaling within nerve terminals, driving excessive synaptic growth. Blocking aberrant signaling from endosomes or reducing BMP activity ameliorates the severity of HD pathology and improves viability. Pathogenic Htt is present largely in a nonaggregated form at synapses, indicating that cytosolic forms of the protein are likely to be the toxic species that disrupt endosomal signaling. Our data indicate that pathogenic Htt acts locally at nerve terminals to alter trafficking between endosomal compartments, leading to defects in synaptic structure that correlate with pathogenesis and lethality in the Drosophila HD model.SIGNIFICANCE STATEMENT Huntington's disease (HD) is the most commonly inherited polyglutamine expansion disorder, but how mutant Huntingtin (Htt) disrupts neuronal function is unclear. In particular, it is unknown within what subcellular compartment pathogenic Htt acts and whether the pathogenesis is associated with aggregated or more soluble forms of the protein. Using a Drosophila HD model, we find that nonaggregated pathogenic Htt acts locally at synaptic terminals to disrupt endosomal compartments, leading to aberrant wiring defects. Genetic manipulations to increase endosomal trafficking of synaptic growth receptors from signaling endosomes or to reduce BMP signaling reduce pathology in this HD model. These data indicate that pathogenic Htt can act locally within nerve terminals to disrupt synaptic endosomal signaling and induce neuropathology.
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12
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Banerjee S, Venkatesan A, Bhat MA. Neurexin, Neuroligin and Wishful Thinking coordinate synaptic cytoarchitecture and growth at neuromuscular junctions. Mol Cell Neurosci 2016; 78:9-24. [PMID: 27838296 DOI: 10.1016/j.mcn.2016.11.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 09/19/2016] [Accepted: 11/09/2016] [Indexed: 10/20/2022] Open
Abstract
Trans-synaptic interactions involving Neurexins and Neuroligins are thought to promote adhesive interactions for precise alignment of the pre- and postsynaptic compartments and organize synaptic macromolecular complexes across species. In Drosophila, while Neurexin (Dnrx) and Neuroligins (Dnlg) are emerging as central organizing molecules at synapses, very little is known of the spectrum of proteins that might be recruited to the Dnrx/Dnlg trans-synaptic interface for organization and growth of the synapses. Using full length and truncated forms of Dnrx and Dnlg1 together with cell biological analyses and genetic interactions, we report novel functions of Dnrx and Dnlg1 in clustering of pre- and postsynaptic proteins, coordination of synaptic growth and ultrastructural organization. We show that Dnrx and Dnlg1 extracellular and intracellular regions are required for proper synaptic growth and localization of Dnlg1 and Dnrx, respectively. dnrx and dnlg1 single and double mutants display altered subcellular distribution of Discs large (Dlg), which is the homolog of mammalian post-synaptic density protein, PSD95. dnrx and dnlg1 mutants also display ultrastructural defects ranging from abnormal active zones, misformed pre- and post-synaptic areas with underdeveloped subsynaptic reticulum. Interestingly, dnrx and dnlg1 mutants have reduced levels of the Bone Morphogenetic Protein (BMP) receptor Wishful thinking (Wit), and Dnrx and Dnlg1 are required for proper localization and stability of Wit. In addition, the synaptic overgrowth phenotype resulting from the overexpression of Dnrx fails to manifest in wit mutants. Phenotypic analyses of dnrx/wit and dnlg1/wit mutants indicate that Dnrx/Dnlg1/Wit coordinate synaptic growth and architecture at the NMJ. Our findings also demonstrate that loss of Dnrx and Dnlg1 leads to decreased levels of the BMP co-receptor, Thickveins and the downstream effector phosphorylated Mad at the Neuromuscular Junction (NMJ) synapses indicating that Dnrx/Dnlg1 regulate components of the BMP signaling pathway. Together our findings reveal that Dnrx/Dnlg are at the core of a highly orchestrated process that combines adhesive and signaling mechanisms to ensure proper synaptic organization and growth during NMJ development.
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Affiliation(s)
- Swati Banerjee
- Department of Cellular and Integrative Physiology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA.
| | - Anandakrishnan Venkatesan
- Department of Cellular and Integrative Physiology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
| | - Manzoor A Bhat
- Department of Cellular and Integrative Physiology, School of Medicine, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA
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13
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Deshpande M, Feiger Z, Shilton AK, Luo CC, Silverman E, Rodal AA. Role of BMP receptor traffic in synaptic growth defects in an ALS model. Mol Biol Cell 2016; 27:2898-910. [PMID: 27535427 PMCID: PMC5042577 DOI: 10.1091/mbc.e16-07-0519] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 08/03/2016] [Indexed: 12/12/2022] Open
Abstract
In a Drosophila model of ALS, neuronal defects are associated with altered endosomal traffic of growth factor receptors and loss of growth-promoting signals. Manipulation of an endosomal recycling pathway suppresses these neuronal defects. The findings suggest that rerouting membrane traffic could be therapeutic in ALS. TAR DNA-binding protein 43 (TDP-43) is genetically and functionally linked to amyotrophic lateral sclerosis (ALS) and regulates transcription, splicing, and transport of thousands of RNA targets that function in diverse cellular pathways. In ALS, pathologically altered TDP-43 is believed to lead to disease by toxic gain-of-function effects on RNA metabolism, as well as by sequestering endogenous TDP-43 and causing its loss of function. However, it is unclear which of the numerous cellular processes disrupted downstream of TDP-43 dysfunction lead to neurodegeneration. Here we found that both loss and gain of function of TDP-43 in Drosophila cause a reduction of synaptic growth–promoting bone morphogenic protein (BMP) signaling at the neuromuscular junction (NMJ). Further, we observed a shift of BMP receptors from early to recycling endosomes and increased mobility of BMP receptor–containing compartments at the NMJ. Inhibition of the recycling endosome GTPase Rab11 partially rescued TDP-43–induced defects in BMP receptor dynamics and distribution and suppressed BMP signaling, synaptic growth, and larval crawling defects. Our results indicate that defects in receptor traffic lead to neuronal dysfunction downstream of TDP-43 misregulation and that rerouting receptor traffic may be a viable strategy for rescuing neurological impairment.
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Affiliation(s)
| | - Zachary Feiger
- Department of Biology, Brandeis University, Waltham, MA 02453
| | | | - Christina C Luo
- Department of Biology, Brandeis University, Waltham, MA 02453
| | - Ethan Silverman
- Department of Biology, Brandeis University, Waltham, MA 02453
| | - Avital A Rodal
- Department of Biology, Brandeis University, Waltham, MA 02453
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14
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The Extracellular and Cytoplasmic Domains of Syndecan Cooperate Postsynaptically to Promote Synapse Growth at the Drosophila Neuromuscular Junction. PLoS One 2016; 11:e0151621. [PMID: 26987116 PMCID: PMC4795781 DOI: 10.1371/journal.pone.0151621] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 03/01/2016] [Indexed: 11/19/2022] Open
Abstract
The heparan sulfate proteoglycan (HSPG) Syndecan (Sdc) is a crucial regulator of synapse development and growth in both vertebrates and invertebrates. In Drosophila, Sdc binds via its extracellular heparan sulfate (HS) sidechains to the receptor protein tyrosine phosphatase LAR to promote the morphological growth of the neuromuscular junction (NMJ). To date, however, little else is known about the molecular mechanisms by which Sdc functions to promote synapse growth. Here we show that all detectable Sdc found at the NMJ is provided by the muscle, strongly suggesting a post-synaptic role for Sdc. We also show that both the cytoplasmic and extracellular domains of Sdc are required to promote synapse growth or to rescue Sdc loss of function. We report the results of a yeast two-hybrid screen using the cytoplasmic domains of Sdc as bait, and identify several novel candidate binding partners for the cytoplasmic domains of Sdc. Together, these studies provide new insight into the mechanism of Sdc function at the NMJ, and provide enticing future directions for further exploring how Sdc promotes synapse growth.
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15
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Sulkowski MJ, Han TH, Ott C, Wang Q, Verheyen EM, Lippincott-Schwartz J, Serpe M. A Novel, Noncanonical BMP Pathway Modulates Synapse Maturation at the Drosophila Neuromuscular Junction. PLoS Genet 2016; 12:e1005810. [PMID: 26815659 PMCID: PMC4729469 DOI: 10.1371/journal.pgen.1005810] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 12/22/2015] [Indexed: 12/21/2022] Open
Abstract
At the Drosophila NMJ, BMP signaling is critical for synapse growth and homeostasis. Signaling by the BMP7 homolog, Gbb, in motor neurons triggers a canonical pathway—which modulates transcription of BMP target genes, and a noncanonical pathway—which connects local BMP/BMP receptor complexes with the cytoskeleton. Here we describe a novel noncanonical BMP pathway characterized by the accumulation of the pathway effector, the phosphorylated Smad (pMad), at synaptic sites. Using genetic epistasis, histology, super resolution microscopy, and electrophysiology approaches we demonstrate that this novel pathway is genetically distinguishable from all other known BMP signaling cascades. This novel pathway does not require Gbb, but depends on presynaptic BMP receptors and specific postsynaptic glutamate receptor subtypes, the type-A receptors. Synaptic pMad is coordinated to BMP’s role in the transcriptional control of target genes by shared pathway components, but it has no role in the regulation of NMJ growth. Instead, selective disruption of presynaptic pMad accumulation reduces the postsynaptic levels of type-A receptors, revealing a positive feedback loop which appears to function to stabilize active type-A receptors at synaptic sites. Thus, BMP pathway may monitor synapse activity then function to adjust synapse growth and maturation during development. Synaptic activity and synapse development are intimately linked, but our understanding of the coupling mechanisms remains limited. Anterograde and retrograde signals together with trans-synaptic complexes enable intercellular communications. How synapse activity status is monitored and relayed across the synaptic cleft remains poorly understood. The Drosophila NMJ is a very powerful genetic system to study synapse development. BMP signaling modulates NMJ growth via a canonical, Smad-dependent pathway, but also synapse stability, via a noncanonical, Smad-independent pathway. Here we describe a novel, noncanonical BMP pathway, which is genetically distinguishable from all other known BMP pathways. This pathway does not contribute to NMJ growth and instead influences synapse formation and maturation in an activity-dependent manner. Specifically, phosphorylated Smad (pMad in flies) accumulates at active zone in response to active postsynaptic type-A glutamate receptors, a specific receptor subtype. In turn, synaptic pMad functions to promote the recruitment of type-A receptors at synaptic sites. This positive feedback loop provides a molecular switch controlling which flavor of glutamate receptors will be stabilized at synaptic locations as a function of synapse status. Since BMP signaling also controls NMJ growth and stability, BMP pathway offers an exquisite means to monitor the status of synapse activity and coordinate NMJ growth with synapse maturation and stabilization.
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Affiliation(s)
- Mikolaj J. Sulkowski
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Tae Hee Han
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Carolyn Ott
- Cellular Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Qi Wang
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Esther M. Verheyen
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Jennifer Lippincott-Schwartz
- Cellular Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
| | - Mihaela Serpe
- Program in Cellular Regulation and Metabolism, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health (NIH), Bethesda, Maryland, United States of America
- * E-mail:
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16
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Harris KP, Littleton JT. Transmission, Development, and Plasticity of Synapses. Genetics 2015; 201:345-75. [PMID: 26447126 PMCID: PMC4596655 DOI: 10.1534/genetics.115.176529] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/28/2015] [Indexed: 01/03/2023] Open
Abstract
Chemical synapses are sites of contact and information transfer between a neuron and its partner cell. Each synapse is a specialized junction, where the presynaptic cell assembles machinery for the release of neurotransmitter, and the postsynaptic cell assembles components to receive and integrate this signal. Synapses also exhibit plasticity, during which synaptic function and/or structure are modified in response to activity. With a robust panel of genetic, imaging, and electrophysiology approaches, and strong evolutionary conservation of molecular components, Drosophila has emerged as an essential model system for investigating the mechanisms underlying synaptic assembly, function, and plasticity. We will discuss techniques for studying synapses in Drosophila, with a focus on the larval neuromuscular junction (NMJ), a well-established model glutamatergic synapse. Vesicle fusion, which underlies synaptic release of neurotransmitters, has been well characterized at this synapse. In addition, studies of synaptic assembly and organization of active zones and postsynaptic densities have revealed pathways that coordinate those events across the synaptic cleft. We will also review modes of synaptic growth and plasticity at the fly NMJ, and discuss how pre- and postsynaptic cells communicate to regulate plasticity in response to activity.
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Affiliation(s)
- Kathryn P Harris
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - J Troy Littleton
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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17
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Inaba M, Buszczak M, Yamashita YM. Nanotubes mediate niche-stem-cell signalling in the Drosophila testis. Nature 2015; 523:329-32. [PMID: 26131929 PMCID: PMC4586072 DOI: 10.1038/nature14602] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 06/01/2015] [Indexed: 12/15/2022]
Abstract
Stem cell niches provide resident stem cells with signals that specify their identity. Niche signals act over a short range such that only stem cells but not their differentiating progeny receive the self-renewing signals. However, the cellular mechanisms that limit niche signalling to stem cells remain poorly understood. Here we show that the Drosophila male germline stem cells form previously unrecognized structures, microtubule-based nanotubes, which extend into the hub, a major niche component. Microtubule-based nanotubes are observed specifically within germline stem cell populations, and require intraflagellar transport proteins for their formation. The bone morphogenetic protein (BMP) receptor Tkv localizes to microtubule-based nanotubes. Perturbation of microtubule-based nanotubes compromises activation of Dpp signalling within germline stem cells, leading to germline stem cell loss. Moreover, Dpp ligand and Tkv receptor interaction is necessary and sufficient for microtubule-based nanotube formation. We propose that microtubule-based nanotubes provide a novel mechanism for selective receptor-ligand interaction, contributing to the short-range nature of niche-stem-cell signalling.
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Affiliation(s)
- Mayu Inaba
- 1] Life Sciences Institute, Department of Cell and Developmental Biology Medical School, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Howard Hughes Medical Institute, University of Michigan Ann Arbor, Michigan 48109, USA [3] Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
| | - Michael Buszczak
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA
| | - Yukiko M Yamashita
- 1] Life Sciences Institute, Department of Cell and Developmental Biology Medical School, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Howard Hughes Medical Institute, University of Michigan Ann Arbor, Michigan 48109, USA
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18
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Crimpy enables discrimination of presynaptic and postsynaptic pools of a BMP at the Drosophila neuromuscular junction. Dev Cell 2014; 31:586-98. [PMID: 25453556 DOI: 10.1016/j.devcel.2014.10.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 09/07/2014] [Accepted: 10/03/2014] [Indexed: 01/22/2023]
Abstract
Distinct pools of the bone morphogenetic protein (BMP) Glass bottom boat (Gbb) control structure and function of the Drosophila neuromuscular junction. Specifically, motoneuron-derived Gbb regulates baseline neurotransmitter release, whereas muscle-derived Gbb regulates neuromuscular junction growth. Yet how cells differentiate between these ligand pools is not known. Here we present evidence that the neuronal Gbb-binding protein Crimpy (Cmpy) permits discrimination of pre- and postsynaptic ligand by serving sequential functions in Gbb signaling. Cmpy first delivers Gbb to dense core vesicles (DCVs) for activity-dependent release from presynaptic terminals. In the absence of Cmpy, Gbb is no longer associated with DCVs and is not released by activity. Electrophysiological analyses demonstrate that Cmpy promotes Gbb's proneurotransmission function. Surprisingly, the Cmpy ectodomain is itself released upon DCV exocytosis, arguing that Cmpy serves a second function in BMP signaling. In addition to trafficking Gbb to DCVs, we propose that Gbb/Cmpy corelease from presynaptic terminals defines a neuronal protransmission signal.
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19
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Retrograde BMP signaling modulates rapid activity-dependent synaptic growth via presynaptic LIM kinase regulation of cofilin. J Neurosci 2014; 34:4371-81. [PMID: 24647957 DOI: 10.1523/jneurosci.4943-13.2014] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The Drosophila neuromuscular junction (NMJ) is capable of rapidly budding new presynaptic varicosities over the course of minutes in response to elevated neuronal activity. Using live imaging of synaptic growth, we characterized this dynamic process and demonstrated that rapid bouton budding requires retrograde bone morphogenic protein (BMP) signaling and local alteration in the presynaptic actin cytoskeleton. BMP acts during development to provide competence for rapid synaptic growth by regulating the levels of the Rho-type guanine nucleotide exchange factor Trio, a transcriptional output of BMP-Smad signaling. In a parallel pathway, we find that the BMP type II receptor Wit signals through the effector protein LIM domain kinase 1 (Limk) to regulate bouton budding. Limk interfaces with structural plasticity by controlling the activity of the actin depolymerizing protein Cofilin. Expression of constitutively active or inactive Cofilin in motor neurons demonstrates that increased Cofilin activity promotes rapid bouton formation in response to elevated synaptic activity. Correspondingly, the overexpression of Limk, which inhibits Cofilin, inhibits bouton budding. Live imaging of the presynaptic F-actin cytoskeleton reveals that activity-dependent bouton addition is accompanied by the formation of new F-actin puncta at sites of synaptic growth. Pharmacological disruption of actin turnover inhibits bouton budding, indicating that local changes in the actin cytoskeleton at pre-existing boutons precede new budding events. We propose that developmental BMP signaling potentiates NMJs for rapid activity-dependent structural plasticity that is achieved by muscle release of retrograde signals that regulate local presynaptic actin cytoskeletal dynamics.
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20
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dAcsl, the Drosophila ortholog of acyl-CoA synthetase long-chain family member 3 and 4, inhibits synapse growth by attenuating bone morphogenetic protein signaling via endocytic recycling. J Neurosci 2014; 34:2785-96. [PMID: 24553921 DOI: 10.1523/jneurosci.3547-13.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Fatty acid metabolism plays an important role in brain development and function. Mutations in acyl-CoA synthetase long-chain family member 4 (ACSL4), which converts long-chain fatty acids to acyl-CoAs, result in nonsyndromic X-linked mental retardation. ACSL4 is highly expressed in the hippocampus, a structure critical for learning and memory. However, the underlying mechanism by which mutations of ACSL4 lead to mental retardation remains poorly understood. We report here that dAcsl, the Drosophila ortholog of ACSL4 and ACSL3, inhibits synaptic growth by attenuating BMP signaling, a major growth-promoting pathway at neuromuscular junction (NMJ) synapses. Specifically, dAcsl mutants exhibited NMJ overgrowth that was suppressed by reducing the doses of the BMP pathway components, accompanied by increased levels of activated BMP receptor Thickveins (Tkv) and phosphorylated mothers against decapentaplegic (Mad), the effector of the BMP signaling at NMJ terminals. In addition, Rab11, a small GTPase involved in endosomal recycling, was mislocalized in dAcsl mutant NMJs, and the membrane association of Rab11 was reduced in dAcsl mutant brains. Consistently, the BMP receptor Tkv accumulated in early endosomes but reduced in recycling endosomes in dAcsl mutant NMJs. dAcsl was also required for the recycling of photoreceptor rhodopsin in the eyes, implying a general role for dAcsl in regulating endocytic recycling of membrane receptors. Importantly, expression of human ACSL4 rescued the endocytic trafficking and NMJ phenotypes of dAcsl mutants. Together, our results reveal a novel mechanism whereby dAcsl facilitates Rab11-dependent receptor recycling and provide insights into the pathogenesis of ACSL4-related mental retardation.
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21
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Sulkowski M, Kim YJ, Serpe M. Postsynaptic glutamate receptors regulate local BMP signaling at the Drosophila neuromuscular junction. Development 2013; 141:436-47. [PMID: 24353060 DOI: 10.1242/dev.097758] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Effective communication between pre- and postsynaptic compartments is required for proper synapse development and function. At the Drosophila neuromuscular junction (NMJ), a retrograde BMP signal functions to promote synapse growth, stability and homeostasis and coordinates the growth of synaptic structures. Retrograde BMP signaling triggers accumulation of the pathway effector pMad in motoneuron nuclei and at synaptic termini. Nuclear pMad, in conjunction with transcription factors, modulates the expression of target genes and instructs synaptic growth; a role for synaptic pMad remains to be determined. Here, we report that pMad signals are selectively lost at NMJ synapses with reduced postsynaptic sensitivities. Despite this loss of synaptic pMad, nuclear pMad persisted in motoneuron nuclei, and expression of BMP target genes was unaffected, indicating a specific impairment in pMad production/maintenance at synaptic termini. During development, synaptic pMad accumulation followed the arrival and clustering of ionotropic glutamate receptors (iGluRs) at NMJ synapses. Synaptic pMad was lost at NMJ synapses developing at suboptimal levels of iGluRs and Neto, an auxiliary subunit required for functional iGluRs. Genetic manipulations of non-essential iGluR subunits revealed that synaptic pMad signals specifically correlated with the postsynaptic type-A glutamate receptors. Altering type-A receptor activities via protein kinase A (PKA) revealed that synaptic pMad depends on the activity and not the net levels of postsynaptic type-A receptors. Thus, synaptic pMad functions as a local sensor for NMJ synapse activity and has the potential to coordinate synaptic activity with a BMP retrograde signal required for synapse growth and homeostasis.
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Affiliation(s)
- Mikolaj Sulkowski
- Program in Cellular Regulation and Metabolism, NICHD, NIH, Bethesda, MD 20892, USA
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22
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Poon VY, Choi S, Park M. Growth factors in synaptic function. Front Synaptic Neurosci 2013; 5:6. [PMID: 24065916 PMCID: PMC3776238 DOI: 10.3389/fnsyn.2013.00006] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 08/29/2013] [Indexed: 12/15/2022] Open
Abstract
Synapses are increasingly recognized as key structures that malfunction in disorders like schizophrenia, mental retardation, and neurodegenerative diseases. The importance and complexity of the synapse has fuelled research into the molecular mechanisms underlying synaptogenesis, synaptic transmission, and plasticity. In this regard, neurotrophic factors such as netrin, Wnt, transforming growth factor-β (TGF-β), tumor necrosis factor-α (TNF-α), and others have gained prominence for their ability to regulate synaptic function. Several of these factors were first implicated in neuroprotection, neuronal growth, and axon guidance. However, their roles in synaptic development and function have become increasingly clear, and the downstream signaling pathways employed by these factors have begun to be elucidated. In this review, we will address the role of these factors and their downstream effectors in synaptic function in vivo and in cultured neurons.
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Affiliation(s)
- Vivian Y Poon
- Neuroscience and Behavioral Disorders Program, Duke-NUS Graduate Medical School Singapore, Singapore
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23
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Clarke DC, Skiba PF. Rationale and resources for teaching the mathematical modeling of athletic training and performance. ADVANCES IN PHYSIOLOGY EDUCATION 2013; 37:134-152. [PMID: 23728131 DOI: 10.1152/advan.00078.2011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A number of professions rely on exercise prescription to improve health or athletic performance, including coaching, fitness/personal training, rehabilitation, and exercise physiology. It is therefore advisable that the professionals involved learn the various tools available for designing effective training programs. Mathematical modeling of athletic training and performance, which we henceforth call "performance modeling," is one such tool. Two models, the critical power (CP) model and the Banister impulse-response (IR) model, offer complementary information. The CP model describes the relationship between work rates and the durations for which an individual can sustain them during constant-work-rate or intermittent exercise. The IR model describes the dynamics by which an individual's performance capacity changes over time as a function of training. Both models elegantly abstract the underlying physiology, and both can accurately fit performance data, such that educating exercise practitioners in the science of performance modeling offers both pedagogical and practical benefits. In addition, performance modeling offers an avenue for introducing mathematical modeling skills to exercise physiology researchers. A principal limitation to the adoption of performance modeling is a lack of education. The goal of this report is therefore to encourage educators of exercise physiology practitioners and researchers to incorporate the science of performance modeling in their curricula and to serve as a resource to support this effort. The resources include a comprehensive review of the concepts associated with the development and use of the models, software to enable hands-on computer exercises, and strategies for teaching the models to different audiences.
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Affiliation(s)
- David C Clarke
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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24
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Fuentes-Medel Y, Ashley J, Barria R, Maloney R, Freeman M, Budnik V. Integration of a retrograde signal during synapse formation by glia-secreted TGF-β ligand. Curr Biol 2012; 22:1831-8. [PMID: 22959350 DOI: 10.1016/j.cub.2012.07.063] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 06/27/2012] [Accepted: 07/27/2012] [Indexed: 10/27/2022]
Abstract
Glial cells are crucial regulators of synapse formation, elimination, and plasticity [1, 2]. In vitro studies have begun to identify glial-derived synaptogenic factors [1], but neuron-glia signaling events during synapse formation in vivo remain poorly defined. The coordinated development of pre- and postsynaptic compartments at the Drosophila neuromuscular junction (NMJ) depends on a muscle-secreted retrograde signal, the TGF-β/BMP Glass bottom boat (Gbb) [3, 4]. Muscle-derived Gbb activates the TGF-β receptors Wishful thinking (Wit) and either Saxophone (Sax) or Thick veins (Tkv) in motor neurons [3, 4]. This induces phosphorylation of Mad (P-Mad) in motor neurons, its translocation into the nucleus with a co-Smad, and activation of transcriptional programs controlling presynaptic bouton growth [5]. Here we show that NMJ glia release the TGF-β ligand Maverick (Mav), which likely activates the muscle activin-type receptor Punt to potently modulate Gbb-dependent retrograde signaling and synaptic growth. Loss of glial Mav results in strikingly reduced P-Mad at NMJs, decreased Gbb transcription in muscle, and in turn reduced muscle-to-motor neuron retrograde TGF-β/BMP signaling. We propose that by controlling Gbb release from muscle, glial cells fine tune the ability of motor neurons to extend new synaptic boutons in correlation to muscle growth. Our work identifies a novel glia-derived synaptogenic factor by which glia modulate synapse formation in vivo.
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Affiliation(s)
- Yuly Fuentes-Medel
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605-2324, USA
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25
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Smith RB, Machamer JB, Kim NC, Hays TS, Marqués G. Relay of retrograde synaptogenic signals through axonal transport of BMP receptors. J Cell Sci 2012; 125:3752-64. [PMID: 22573823 DOI: 10.1242/jcs.094292] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neuronal function depends on the retrograde relay of growth and survival signals from the synaptic terminal, where the neuron interacts with its targets, to the nucleus, where gene transcription is regulated. Activation of the Bone Morphogenetic Protein (BMP) pathway at the Drosophila larval neuromuscular junction results in nuclear accumulation of the phosphorylated form of the transcription factor Mad in the motoneuron nucleus. This in turn regulates transcription of genes that control synaptic growth. How BMP signaling at the synaptic terminal is relayed to the cell body and nucleus of the motoneuron to regulate transcription is unknown. We show that the BMP receptors are endocytosed at the synaptic terminal and transported retrogradely along the axon. Furthermore, this transport is dependent on BMP pathway activity, as it decreases in the absence of ligand or receptors. We further demonstrate that receptor traffic is severely impaired when Dynein motors are inhibited, a condition that has previously been shown to block BMP pathway activation. In contrast to these results, we find no evidence for transport of phosphorylated Mad along the axons, and axonal traffic of Mad is not affected in mutants defective in BMP signaling or retrograde transport. These data support a model in which complexes of activated BMP receptors are actively transported along the axon towards the cell body to relay the synaptogenic signal, and that phosphorylated Mad at the synaptic terminal and cell body represent two distinct molecular populations.
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Affiliation(s)
- Rebecca B Smith
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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26
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Krieglstein K, Zheng F, Unsicker K, Alzheimer C. More than being protective: functional roles for TGF-β/activin signaling pathways at central synapses. Trends Neurosci 2011; 34:421-9. [PMID: 21742388 DOI: 10.1016/j.tins.2011.06.002] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 05/30/2011] [Accepted: 06/01/2011] [Indexed: 12/14/2022]
Abstract
It is becoming increasingly clear that members of the transforming growth factor-β (TGF-β) family have roles in the central nervous system that extend beyond their well-established roles as neurotrophic and neuroprotective factors. Recent findings have indicated that the TGF-β signaling pathways are involved in the modulation of both excitatory and inhibitory synaptic transmission in the adult mammalian brain. In this review, we discuss how TGF-β, bone morphogenetic protein and activin signaling at central synapses modulate synaptic plasticity, cognition and affective behavior. We also discuss the implications of these findings for the molecular understanding and potential treatment of neuropsychiatric diseases, such as anxiety, depression and other neurological disorders.
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Affiliation(s)
- Kerstin Krieglstein
- Institute of Anatomy and Cell Biology, University of Freiburg, 79104 Freiburg, Germany
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27
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James RE, Broihier HT. Crimpy inhibits the BMP homolog Gbb in motoneurons to enable proper growth control at the Drosophila neuromuscular junction. Development 2011; 138:3273-86. [PMID: 21750037 DOI: 10.1242/dev.066142] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The BMP pathway is essential for scaling of the presynaptic motoneuron arbor to the postsynaptic muscle cell at the Drosophila neuromuscular junction (NMJ). Genetic analyses indicate that the muscle is the BMP-sending cell and the motoneuron is the BMP-receiving cell. Nevertheless, it is unclear how this directionality is established as Glass bottom boat (Gbb), the known BMP ligand, is active in motoneurons. We demonstrate that crimpy (cmpy) limits neuronal Gbb activity to permit appropriate regulation of NMJ growth. cmpy was identified in a screen for motoneuron-expressed genes and encodes a single-pass transmembrane protein with sequence homology to vertebrate Cysteine-rich transmembrane BMP regulator 1 (Crim1). We generated a targeted deletion of the cmpy locus and find that loss-of-function mutants exhibit excessive NMJ growth. In accordance with its expression profile, tissue-specific rescue experiments indicate that cmpy functions neuronally. The overgrowth in cmpy mutants depends on the activity of the BMP type II receptor Wishful thinking, arguing that Cmpy acts in the BMP pathway upstream of receptor activation and raising the possibility that it inhibits Gbb activity in motoneurons. Indeed, the cmpy mutant phenotype is strongly suppressed by RNAi-mediated knockdown of Gbb in motoneurons. Furthermore, Cmpy physically interacts with the Gbb precursor protein, arguing that Cmpy binds Gbb prior to the secretion of mature ligand. These studies demonstrate that Cmpy restrains Gbb activity in motoneurons. We present a model whereby this inhibition permits the muscle-derived Gbb pool to predominate at the NMJ, thus establishing the retrograde directionality of the pro-growth BMP pathway.
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Affiliation(s)
- Rebecca E James
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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28
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Abstract
The development of multicellular organisms requires the well balanced and coordinated migration of many cell types. This is of particular importance within the developing nervous system, where glial cells often move long distances to reach their targets. The majority of glial cells in the peripheral nervous system of the Drosophila embryo is derived from the CNS and migrates along motor axons toward their targets. In the developing Drosophila eye, CNS-derived glial cells move outward toward the nascent photoreceptor cells, but the molecular mechanisms coupling the migration of glial cells with the growth of the eye imaginal disc are mostly unknown. Here, we used an enhancer trap approach to identify the gene spinster, which encodes a multipass transmembrane protein involved in endosome-lysosome trafficking, as being expressed in many glial cells. spinster mutants are characterized by glial overmigration. Genetic experiments demonstrate that Spinster modulates the activity of several signaling cascades. Within the migrating perineurial glial cells, Spinster is required to downregulate Dpp (Decapentaplegic) signaling activity, which ceases migratory abilities. In addition, Spinster affects the growth of the carpet cell, which indirectly modulates glial migration.
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29
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Oct4 kinetics predict cell lineage patterning in the early mammalian embryo. Nat Cell Biol 2011; 13:117-23. [PMID: 21258368 DOI: 10.1038/ncb2154] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2010] [Accepted: 11/07/2010] [Indexed: 12/13/2022]
Abstract
Transcription factors are central to sustaining pluripotency, yet little is known about transcription factor dynamics in defining pluripotency in the early mammalian embryo. Here, we establish a fluorescence decay after photoactivation (FDAP) assay to quantitatively study the kinetic behaviour of Oct4, a key transcription factor controlling pre-implantation development in the mouse embryo. FDAP measurements reveal that each cell in a developing embryo shows one of two distinct Oct4 kinetics, before there are any morphologically distinguishable differences or outward signs of lineage patterning. The differences revealed by FDAP are due to differences in the accessibility of Oct4 to its DNA binding sites in the nucleus. Lineage tracing of the cells in the two distinct sub-populations demonstrates that the Oct4 kinetics predict lineages of the early embryo. Cells with slower Oct4 kinetics are more likely to give rise to the pluripotent cell lineage that contributes to the inner cell mass. Those with faster Oct4 kinetics contribute mostly to the extra-embryonic lineage. Our findings identify Oct4 kinetics, rather than differences in total transcription factor expression levels, as a predictive measure of developmental cell lineage patterning in the early mouse embryo.
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30
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Lone M, Kungl T, Koper A, Bottenberg W, Kammerer R, Klein M, Sweeney ST, Auburn RP, O'Kane CJ, Prokop A. The nuclear protein Waharan is required for endosomal-lysosomal trafficking in Drosophila. J Cell Sci 2010; 123:2369-74. [PMID: 20551180 DOI: 10.1242/jcs.060582] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Here we report Drosophila Waharan (Wah), a 170-kD predominantly nuclear protein with two potential human homologues, as a newly identified regulator of endosomal trafficking. Wah is required for neuromuscular-junction development and muscle integrity. In muscles, knockdown of Wah caused novel accumulations of tightly packed electron-dense tubules, which we termed 'sausage bodies'. Our data suggest that sausage bodies coincide with sites at which ubiquitylated proteins and a number of endosomal and lysosomal markers co-accumulate. Furthermore, loss of Wah function generated loss of the acidic LysoTracker compartment. Together with data demonstrating that Wah acts earlier in the trafficking pathway than the Escrt-III component Drosophila Shrb (snf7 in Schizosaccharomyces pombe), our results indicate that Wah is essential for endocytic trafficking at the late endosome. Highly unexpected phenotypes result from Wah knockdown, in that the distribution of ubiquitylated cargos and endolysosomal morphologies are affected despite Wah being a predominant nuclear protein. This finding suggests the existence of a relationship between nuclear functions and endolysosomal trafficking. Future studies of Wah function will give us insights into this interesting phenomenon.
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Affiliation(s)
- Mohiddin Lone
- Faculty of Life Sciences, The University of Manchester, Oxford Road, M13 9PT Manchester, UK
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Abstract
In flies, retrograde BMP signaling is an important mechanism by which postsynaptic cells regulate the structure and function of presynaptic terminals, ostensibly through changes in gene expression. Transcriptional targets, however, have remained mysterious. In this issue of Neuron, Haghighi and colleagues begin to unravel this puzzle by identifying the cytoskeletal regulator Trio.
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Affiliation(s)
- Yuly Fuentes-Medel
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Vivian Budnik
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Importin-beta11 regulates synaptic phosphorylated mothers against decapentaplegic, and thereby influences synaptic development and function at the Drosophila neuromuscular junction. J Neurosci 2010; 30:5253-68. [PMID: 20392948 DOI: 10.1523/jneurosci.3739-09.2010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Importin proteins act both at the nuclear pore to promote substrate entry and in the cytosol during signal trafficking. Here, we describe mutations in the Drosophila gene importin-beta11, which has not previously been analyzed genetically. Mutants of importin-beta11 died as late pupae from neuronal defects, and neuronal importin-beta11 was present not only at nuclear pores but also in the cytosol and at synapses. Neurons lacking importin-beta11 were viable and properly differentiated but exhibited discrete defects. Synaptic transmission was defective in adult photoreceptors and at larval neuromuscular junctions (NMJs). Mutant photoreceptor axons formed grossly normal projections and synaptic terminals in the brain, but synaptic arbors on larval muscles were smaller while still containing appropriate synaptic components. Bone morphogenic protein (BMP) signaling was the apparent cause of the observed NMJ defects. Importin-beta11 interacted genetically with the BMP pathway, and at mutant synaptic boutons, a key component of this pathway, phosphorylated mothers against decapentaplegic (pMAD), was reduced. Neuronal expression of an importin-beta11 transgene rescued this phenotype as well as the other observed neuromuscular phenotypes. Despite the loss of synaptic pMAD, pMAD persisted in motor neuron nuclei, suggesting a specific impairment in the local function of pMAD. Restoring levels of pMAD to mutant terminals via expression of constitutively active type I BMP receptors or by reducing retrograde transport in motor neurons also restored synaptic strength and morphology. Thus, importin-beta11 function interacts with the BMP pathway to regulate a pool of pMAD that must be present at the presynapse for its proper development and function.
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33
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Wu H, Xiong WC, Mei L. To build a synapse: signaling pathways in neuromuscular junction assembly. Development 2010; 137:1017-33. [PMID: 20215342 DOI: 10.1242/dev.038711] [Citation(s) in RCA: 379] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Synapses, as fundamental units of the neural circuitry, enable complex behaviors. The neuromuscular junction (NMJ) is a synapse type that forms between motoneurons and skeletal muscle fibers and that exhibits a high degree of subcellular specialization. Aided by genetic techniques and suitable animal models, studies in the past decade have brought significant progress in identifying NMJ components and assembly mechanisms. This review highlights recent advances in the study of NMJ development, focusing on signaling pathways that are activated by diffusible cues, which shed light on synaptogenesis in the brain and contribute to a better understanding of muscular dystrophy.
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Affiliation(s)
- Haitao Wu
- Program of Developmental Neurobiology, Institute of Molecular Medicine and Genetics, Department of Neurology, Medical College of Georgia, Augusta, GA 30912, USA
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34
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The Drosophila LEM-domain protein MAN1 antagonizes BMP signaling at the neuromuscular junction and the wing crossveins. Dev Biol 2009; 339:1-13. [PMID: 20036230 DOI: 10.1016/j.ydbio.2009.11.036] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2009] [Revised: 11/17/2009] [Accepted: 11/19/2009] [Indexed: 01/31/2023]
Abstract
BMP signaling responses are refined by distinct secreted and intracellular antagonists in different cellular and temporal contexts. Here, we show that the nuclear LEM-domain protein MAN1 is a tissue-specific antagonist of BMP signaling in Drosophila. MAN1 contains two potential Mad-binding sites. We generated MAN1DeltaC mutants, harbouring a MAN1 protein that lacks part of the C-terminus including the RNA recognition motif, a putative Mad-binding domain. MAN1DeltaC mutants show wing crossvein (CV) patterning defects but no detectable alterations in nuclear morphology. MAN1(DeltaC) pupal wings display expanded phospho-Mad (pMad) accumulation and ectopic expression of the BMP-responsive gene crossveinless-2 (cv-2) indicating that MAN1 restricts BMP signaling. Conversely, MAN1 overexpression in wing imaginal discs inhibited crossvein development and BMP signaling responses. MAN1 is expressed at high levels in pupal wing veins and can be activated in intervein regions by ectopic BMP signaling. The specific upregulation of MAN1 in pupal wing veins may thus represent a negative feedback circuit that limits BMP signaling during CV formation. MAN1DeltaC flies also show reduced locomotor activity, and electrophysiology recordings in MAN1DeltaC larvae uncover a new presynaptic role of MAN1 at the neuromuscular junction (NMJ). Genetic interaction experiments suggest that MAN1 is a BMP signaling antagonist both at the NMJ and during CV formation.
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35
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Abstract
How morphogen gradients are formed in target tissues is a key question for understanding the mechanisms of morphological patterning. Here, we review different mechanisms of morphogen gradient formation from theoretical and experimental points of view. First, a simple, comprehensive overview of the underlying biophysical principles of several mechanisms of gradient formation is provided. We then discuss the advantages and limitations of different experimental approaches to gradient formation analysis.
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36
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Clarke DC, Liu X. Decoding the quantitative nature of TGF-beta/Smad signaling. Trends Cell Biol 2008; 18:430-42. [PMID: 18706811 DOI: 10.1016/j.tcb.2008.06.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 06/13/2008] [Accepted: 06/17/2008] [Indexed: 01/02/2023]
Abstract
How transforming growth factor-beta (TGF-beta) signaling elicits diverse cell responses remains elusive, despite the major molecular components of the pathway being known. We contend that understanding TGF-beta biology requires mathematical models to decipher the quantitative nature of TGF-beta/Smad signaling and to account for its complexity. Here, we review mathematical models of TGF-beta superfamily signaling that predict how robustness is achieved in bone-morphogenetic-protein signaling in the Drosophila embryo, how changes in receptor-trafficking dynamics can be exploited by cancer cells and how the basic mechanisms of TGF-beta/Smad signaling conspire to promote Smad accumulation in the nucleus. These studies demonstrate the power of mathematical modeling for understanding TGF-beta biology.
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Affiliation(s)
- David C Clarke
- Department of Chemistry and Biochemistry, University of Colorado-Boulder, Boulder, CO 80309-0215, USA
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37
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O'Connor-Giles KM, Ho LL, Ganetzky B. Nervous wreck interacts with thickveins and the endocytic machinery to attenuate retrograde BMP signaling during synaptic growth. Neuron 2008; 58:507-18. [PMID: 18498733 DOI: 10.1016/j.neuron.2008.03.007] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 01/28/2008] [Accepted: 03/10/2008] [Indexed: 11/17/2022]
Abstract
Regulation of synaptic growth is fundamental to the formation and plasticity of neural circuits. Here, we demonstrate that Nervous wreck (Nwk), a negative regulator of synaptic growth at Drosophila NMJs, interacts functionally and physically with components of the endocytic machinery, including dynamin and Dap160/intersectin, and negatively regulates retrograde BMP growth signaling through a direct interaction with the BMP receptor, thickveins. Synaptic overgrowth in nwk is sensitive to BMP signaling levels, and loss of Nwk facilitates BMP-induced overgrowth. Conversely, Nwk overexpression suppresses BMP-induced synaptic overgrowth. We observe analogous genetic interactions between dap160 and the BMP pathway, confirming that endocytosis regulates BMP signaling at NMJs. Finally, we demonstrate a correlation between synaptic growth and pMAD levels and show that Nwk regulates these levels. We propose that Nwk functions at the interface of endocytosis and BMP signaling to ensure proper synaptic growth by negatively regulating Tkv to set limits on this positive growth signal.
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38
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Ratnaparkhi A, Lawless GM, Schweizer FE, Golshani P, Jackson GR. A Drosophila model of ALS: human ALS-associated mutation in VAP33A suggests a dominant negative mechanism. PLoS One 2008; 3:e2334. [PMID: 18523548 PMCID: PMC2390852 DOI: 10.1371/journal.pone.0002334] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2007] [Accepted: 04/25/2008] [Indexed: 01/01/2023] Open
Abstract
ALS8 is caused by a dominant mutation in an evolutionarily conserved protein, VAPB (vesicle-associated membrane protein (VAMP)-associated membrane protein B)/ALS8). We have established a fly model of ALS8 using the corresponding mutation in Drosophila VAPB (dVAP33A) and examined the effects of this mutation on VAP function using genetic and morphological analyses. By simultaneously assessing the effects of VAPwt and VAPP58S on synaptic morphology and structure, we demonstrate that the phenotypes produced by neuronal expression of VAPP58S resemble VAP loss of function mutants and are opposite those of VAP overexpression, suggesting that VAPP58S may function as a dominant negative. This is brought about by aggregation of VAPP58S and recruitment of wild type VAP into these aggregates. Importantly, we also demonstrate that the ALS8 mutation in dVAP33A interferes with BMP signaling pathways at the neuromuscular junction, identifying a new mechanism underlying pathogenesis of ALS8. Furthermore, we show that mutant dVAP33A can serve as a powerful tool to identify genetic modifiers of VAPB. This new fly model of ALS, with its robust pathological phenotypes, should for the first time allow the power of unbiased screens in Drosophila to be applied to study of motor neuron diseases.
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Affiliation(s)
- Anuradha Ratnaparkhi
- Department of Neurology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, United States of America
| | - George M. Lawless
- Department of Neurology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, United States of America
| | - Felix E. Schweizer
- Department of Neurobiology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, United States of America
| | - Peyman Golshani
- Department of Neurology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, United States of America
| | - George R. Jackson
- Department of Neurology, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, United States of America
- Center for Neurobehavioral Genetics, Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine at the University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Mathematical modeling identifies Smad nucleocytoplasmic shuttling as a dynamic signal-interpreting system. Proc Natl Acad Sci U S A 2008; 105:6608-13. [PMID: 18443295 DOI: 10.1073/pnas.0710134105] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
TGF-beta-induced Smad signal transduction from the membrane into the nucleus is not linear and unidirectional, but rather a dynamic network that couples Smad phosphorylation and dephosphorylation through continuous nucleocytoplasmic shuttling of Smads. To understand the quantitative behavior of this network, we have developed a tightly constrained computational model, exploiting the interplay between mathematical modeling and experimental strategies. The model simultaneously reproduces four distinct datasets with excellent accuracy and provides mechanistic insights into how the network operates. We use the model to make predictions about the outcome of fluorescence recovery after photobleaching experiments and the behavior of a functionally impaired Smad2 mutant, which we then verify experimentally. Successful model performance strongly supports the hypothesis of a dynamic maintenance of Smad nuclear accumulation during active signaling. The presented work establishes Smad nucleocytoplasmic shuttling as a dynamic network that flexibly transmits quantitative features of the extracellular TGF-beta signal, such as its duration and intensity, into the nucleus.
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40
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Korolchuk VI, Schütz MM, Gómez-Llorente C, Rocha J, Lansu NR, Collins SM, Wairkar YP, Robinson IM, O'Kane CJ. Drosophila Vps35 function is necessary for normal endocytic trafficking and actin cytoskeleton organisation. J Cell Sci 2008; 120:4367-76. [PMID: 18057029 DOI: 10.1242/jcs.012336] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To identify novel proteins required for receptor-mediated endocytosis, we have developed an RNAi-based screening method in Drosophila S2 cells, based on uptake of a scavenger receptor ligand. Some known endocytic proteins are essential for endocytosis in this assay, including clathrin and alpha-adaptin; however, other proteins important for synaptic vesicle endocytosis are not required. In a small screen for novel endocytic proteins, we identified the Drosophila homologue of Vps35, a component of the retromer complex, involved in endosome-to-Golgi trafficking. Loss of Vps35 inhibits scavenger receptor ligand endocytosis, and causes mislocalisation of a number of receptors and endocytic proteins. Vps35 has tumour suppressor properties because its loss leads to overproliferation of blood cells in larvae. Its loss also causes signalling defects at the neuromuscular junction, including upregulation of TGFbeta/BMP signalling and excessive formation of synaptic terminals. Vps35 negatively regulates actin polymerisation, and genetic interactions suggest that some of the endocytic and signalling defects of vps35 mutants are due to this function.
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Affiliation(s)
- Viktor I Korolchuk
- Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK.
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41
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TGFbeta-SMAD signal transduction: molecular specificity and functional flexibility. Nat Rev Mol Cell Biol 2007; 8:970-82. [PMID: 18000526 DOI: 10.1038/nrm2297] [Citation(s) in RCA: 971] [Impact Index Per Article: 57.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ligands of the transforming growth factor-beta (TGFbeta) superfamily of growth factors initiate signal transduction through a bewildering complexity of ligand-receptor interactions. Signalling then converges to nuclear accumulation of transcriptionally active SMAD complexes and gives rise to a plethora of specific functional responses in both embryos and adult organisms. Current research is focused on the mechanisms that regulate SMAD activity to evoke cell-type-specific and context-dependent transcriptional programmes. An equally important challenge is understanding the functional role of signal strength and duration. How are these quantitative aspects of the extracellular signal regulated? How are they then sensed and interpreted, and how do they affect responses?
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42
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Sun M, Thomas MJ, Herder R, Bofenkamp ML, Selleck SB, O'Connor MB. Presynaptic contributions of chordin to hippocampal plasticity and spatial learning. J Neurosci 2007; 27:7740-50. [PMID: 17634368 PMCID: PMC6672865 DOI: 10.1523/jneurosci.1604-07.2007] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Recently, several evolutionary conserved signaling pathways that play prominent roles in regulating early neurodevelopment have been found to regulate synaptic remodeling in the adult. To test whether adult neuronal expression of bone morphogenic protein (BMP) signaling components also plays a postnatal role in regulating neuronal plasticity, we modulated BMP signaling in mice both in vivo and in vitro by genetic removal of the BMP inhibitor chordin or by perfusing recombinant BMP signaling pathway components onto acute hippocampal slices. Chordin null mice exhibited a significant increase in presynaptic transmitter release from hippocampal neurons, resulting in enhanced paired-pulse facilitation and long-term potentiation. These mice also showed a decreased acquisition time in a water maze test along with less exploratory activity during Y-maze and open-field tests. Perfusion of BMP ligands onto hippocampal slices replicated the presynaptic phenotype of chordin null slices, but bath application of Noggin, another antagonist of BMP signaling pathway, significantly decrease the frequency of miniature EPSCs. These results demonstrate that the BMP signaling pathway contributes to synaptic plasticity and learning likely through a presynaptic mechanism.
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Affiliation(s)
- Mu Sun
- Howard Hughes Medical Institute and
- Departments of Genetics, Cell Biology, and Development
| | | | - Rachel Herder
- Departments of Genetics, Cell Biology, and Development
| | - M. Lisa Bofenkamp
- Howard Hughes Medical Institute and
- Departments of Genetics, Cell Biology, and Development
| | - Scott B. Selleck
- Departments of Genetics, Cell Biology, and Development
- Pediatrics, University of Minnesota, Minneapolis, Minnesota 55455
| | - Michael B. O'Connor
- Howard Hughes Medical Institute and
- Departments of Genetics, Cell Biology, and Development
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43
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Rollmann SM, Yamamoto A, Goossens T, Zwarts L, Callaerts-Végh Z, Callaerts P, Norga K, Mackay TFC, Anholt RRH. The early developmental gene Semaphorin 5c contributes to olfactory behavior in adult Drosophila. Genetics 2007; 176:947-56. [PMID: 17435226 PMCID: PMC1894621 DOI: 10.1534/genetics.106.069781] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Behaviors are complex traits influenced by multiple pleiotropic genes. Understanding the mechanisms that give rise to complex behaviors requires an understanding of how variation in transcriptional regulation shapes nervous system development and how variation in brain structure influences an organism's ability to respond to its environment. To begin to address this problem, we used olfactory behavior in Drosophila melanogaster as a model and showed that a hypomorphic transposon-mediated mutation of the early developmental gene Semaphorin-5c (Sema-5c) results in aberrant behavioral responses to the repellant odorant benzaldehyde. We fine mapped this effect to the Sema-5c locus using deficiency mapping, phenotypic reversion through P-element excision, and transgenic rescue. Morphometric analysis of this Sema-5c allele reveals subtle neuroanatomical changes in the brain with a reduction in the size of the ellipsoid body. High-density oligonucleotide expression microarrays identified 50 probe sets with altered transcriptional regulation in the Sema-5c background and quantitative complementation tests identified epistatic interactions between nine of these coregulated genes and the transposon-disrupted Sema-5c gene. Our results demonstrate how hypomorphic mutation of an early developmental gene results in genomewide transcriptional consequences and alterations in brain structure accompanied by profound impairment of adult behavior.
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Affiliation(s)
- Stephanie M. Rollmann
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Akihiko Yamamoto
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Tim Goossens
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Liesbeth Zwarts
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Zsuzsanna Callaerts-Végh
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Patrick Callaerts
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Koenraad Norga
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Trudy F. C. Mackay
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
| | - Robert R. H. Anholt
- Department of Zoology, Department of Genetics and W. M. Keck Center for Behavioral Biology, North Carolina State University, Raleigh, North Carolina 27695, Laboratory of Developmental Genetics, Center for Human Genetics, B-3000 Leuven, Belgium, Zoological Institute, Department of Biology, B-3000 Leuven, Belgium, Laboratory of Biological Psychology, B-3000 Leuven, Belgium and Children's Hospital, B-3000 Leuven, Belgium
- Corresponding author: W. M. Keck Center for Behavioral Biology, Campus Box 7617, North Carolina State University, Raleigh, NC 27695-7617. E-mail:
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Hadley D, Murphy T, Valladares O, Hannenhalli S, Ungar L, Kim J, Bućan M. Patterns of sequence conservation in presynaptic neural genes. Genome Biol 2007; 7:R105. [PMID: 17096848 PMCID: PMC1794582 DOI: 10.1186/gb-2006-7-11-r105] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 09/25/2006] [Accepted: 11/10/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The neuronal synapse is a fundamental functional unit in the central nervous system of animals. Because synaptic function is evolutionarily conserved, we reasoned that functional sequences of genes and related genomic elements known to play important roles in neurotransmitter release would also be conserved. RESULTS Evolutionary rate analysis revealed that presynaptic proteins evolve slowly, although some members of large gene families exhibit accelerated evolutionary rates relative to other family members. Comparative sequence analysis of 46 megabases spanning 150 presynaptic genes identified more than 26,000 elements that are highly conserved in eight vertebrate species, as well as a small subset of sequences (6%) that are shared among unrelated presynaptic genes. Analysis of large gene families revealed that upstream and intronic regions of closely related family members are extremely divergent. We also identified 504 exceptionally long conserved elements (> or =360 base pairs, > or =80% pair-wise identity between human and other mammals) in intergenic and intronic regions of presynaptic genes. Many of these elements form a highly stable stem-loop RNA structure and consequently are candidates for novel regulatory elements, whereas some conserved noncoding elements are shown to correlate with specific gene expression profiles. The SynapseDB online database integrates these findings and other functional genomic resources for synaptic genes. CONCLUSION Highly conserved elements in nonprotein coding regions of 150 presynaptic genes represent sequences that may be involved in the transcriptional or post-transcriptional regulation of these genes. Furthermore, comparative sequence analysis will facilitate selection of genes and noncoding sequences for future functional studies and analysis of variation studies in neurodevelopmental and psychiatric disorders.
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Affiliation(s)
- Dexter Hadley
- Penn Center for Bioinformatics, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Genomics and Computational Biology Graduate Group, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Tara Murphy
- Department of Genetics in the School of Medicine, University of Pennsylvania, 415 Curie Boulevard Philadelphia, Pennsylvania 19104, USA
- UCLA Neuroscience Graduate Office, 695 Young Drive South, Los Angeles, California 90095, USA
| | - Otto Valladares
- Department of Genetics in the School of Medicine, University of Pennsylvania, 415 Curie Boulevard Philadelphia, Pennsylvania 19104, USA
| | - Sridhar Hannenhalli
- Penn Center for Bioinformatics, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Genomics and Computational Biology Graduate Group, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Lyle Ungar
- Penn Center for Bioinformatics, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Department of Computer & Information Sciences in School of Engineering and Applied Sciences, 3330 Walnut Street, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Junhyong Kim
- Penn Center for Bioinformatics, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Department of Computer & Information Sciences in School of Engineering and Applied Sciences, 3330 Walnut Street, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Department of Biology in the School of Arts and Sciences, 433 S University Avenue, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Maja Bućan
- Penn Center for Bioinformatics, 423 Guardian Drive, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- Department of Genetics in the School of Medicine, University of Pennsylvania, 415 Curie Boulevard Philadelphia, Pennsylvania 19104, USA
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Collins CA, DiAntonio A. Synaptic development: insights from Drosophila. Curr Opin Neurobiol 2007; 17:35-42. [PMID: 17229568 DOI: 10.1016/j.conb.2007.01.001] [Citation(s) in RCA: 197] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 01/04/2007] [Indexed: 01/14/2023]
Abstract
In Drosophila, the larval neuromuscular junction is particularly tractable for studying how synapses develop and function. In contrast to vertebrate central synapses, each presynaptic motor neuron and postsynaptic muscle cell is unique and identifiable, and the wiring circuit is invariant. Thus, the full power of Drosophila genetics can be brought to bear on a single, reproducibly identifiable, synaptic terminal. Each individual neuromuscular junction encompasses hundreds of synaptic neurotransmitter release sites housed in a chain of synaptic boutons. Recent advances have increased our understanding of the mechanisms that shape the development of both individual synapses--that is, the transmitter release sites including active zones and their apposed glutamate receptor clusters--and the whole synaptic terminal that connects a pre- and post-synaptic cell.
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Affiliation(s)
- Catherine A Collins
- Department of Molecular Biology and Pharmacology, Campus Box 8103, 660 South Euclid, Washington University School of Medicine, St Louis, MO 63110, USA
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46
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Wang X, Shaw WR, Tsang HTH, Reid E, O'Kane CJ. Drosophila spichthyin inhibits BMP signaling and regulates synaptic growth and axonal microtubules. Nat Neurosci 2007; 10:177-85. [PMID: 17220882 PMCID: PMC2464677 DOI: 10.1038/nn1841] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Accepted: 12/27/2006] [Indexed: 11/09/2022]
Abstract
To understand the functions of NIPA1, mutated in the neurodegenerative disease hereditary spastic paraplegia, and of ichthyin, mutated in autosomal recessive congenital ichthyosis, we have studied their Drosophila melanogaster ortholog, spichthyin (Spict). Spict is found on early endosomes. Loss of Spict leads to upregulation of bone morphogenetic protein (BMP) signaling and expansion of the neuromuscular junction. BMP signaling is also necessary for a normal microtubule cytoskeleton and axonal transport; analysis of loss- and gain-of-function phenotypes indicate that Spict may antagonize this function of BMP signaling. Spict interacts with BMP receptors and promotes their internalization from the plasma membrane, implying that it inhibits BMP signaling by regulating BMP receptor traffic. This is the first demonstration of a role for a hereditary spastic paraplegia protein or ichthyin family member in a specific signaling pathway, and implies disease mechanisms for hereditary spastic paraplegia that involve dependence of the microtubule cytoskeleton on BMP signaling.
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Affiliation(s)
- Xinnan Wang
- Department of Genetics, University of Cambridge, Downing Street, Cambridge, CB2 3EH, UK
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Reeves GT, Muratov CB, Schüpbach T, Shvartsman SY. Quantitative Models of Developmental Pattern Formation. Dev Cell 2006; 11:289-300. [PMID: 16950121 DOI: 10.1016/j.devcel.2006.08.006] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 08/16/2006] [Accepted: 08/17/2006] [Indexed: 10/24/2022]
Abstract
Pattern formation in developing organisms can be regulated at a variety of levels, from gene sequence to anatomy. At this level of complexity, mechanistic models of development become essential for integrating data, guiding future experiments, and predicting the effects of genetic and physical perturbations. However, the formulation and analysis of quantitative models of development are limited by high levels of uncertainty in experimental measurements, a large number of both known and unknown system components, and the multiscale nature of development. At the same time, an expanding arsenal of experimental tools can constrain models and directly test their predictions, making the modeling efforts not only necessary, but feasible. Using a number of problems in fruit fly development, we discuss how models can be used to test the feasibility of proposed patterning mechanisms and characterize their systems-level properties.
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Affiliation(s)
- Gregory T Reeves
- Department of Chemical Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA
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Marqués G, Zhang B. Retrograde signaling that regulates synaptic development and function at the Drosophila neuromuscular junction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2006; 75:267-85. [PMID: 17137932 DOI: 10.1016/s0074-7742(06)75012-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Guillermo Marqués
- Department of Cell Biology, School of Medicine The University of Alabama at Birmingham, Birmingham Alabama 35294, USA
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Griffith LC, Budnik V. Plasticity and second messengers during synapse development. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2006; 75:237-65. [PMID: 17137931 PMCID: PMC4664443 DOI: 10.1016/s0074-7742(06)75011-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Effective function of the locomotor system in the Drosophila larva requires a continuous adjustment of synaptic architecture and neurotransmission at the neuromuscular junction (NMJ). This feature has made the larval NMJ a favorite model to study the genetic and molecular mechanisms underlying synapse plasticity. This chapter will review experimental strategies used to study plasticity at the NMJ, the cellular parameters affected during plastic changes, and many of the known molecules involved in plastic changes. In addition, signal transduction pathways activated during plasticity will be discussed.
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Affiliation(s)
- Leslie C. Griffith
- Dept of Biology and National Center for Behavioral Genomics, Brandeis University, 415 South St., Waltham, MA, 02454, USA
- Corresponding Author: phone: 781 736 3125, FAX: 781 736 3107,
| | - Vivian Budnik
- Department of Neurobiology, University of Massachusetts Medical School, Aaron Lazare Medical Research Building, 364 Plantation Street Worcester, MA 01605-2324, USA
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