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Goodman KM, Rubinstein R, Thu CA, Bahna F, Mannepalli S, Ahlsén G, Rittenhouse C, Maniatis T, Honig B, Shapiro L. Structural Basis of Diverse Homophilic Recognition by Clustered α- and β-Protocadherins. Neuron 2016; 90:709-23. [PMID: 27161523 DOI: 10.1016/j.neuron.2016.04.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 02/22/2016] [Accepted: 03/30/2016] [Indexed: 10/21/2022]
Abstract
Clustered protocadherin proteins (α-, β-, and γ-Pcdhs) provide a high level of cell-surface diversity to individual vertebrate neurons, engaging in highly specific homophilic interactions to mediate important roles in mammalian neural circuit development. How Pcdhs bind homophilically through their extracellular cadherin (EC) domains among dozens of highly similar isoforms has not been determined. Here, we report crystal structures for extracellular regions from four mouse Pcdh isoforms (α4, α7, β6, and β8), revealing a canonical head-to-tail interaction mode for homophilic trans dimers comprising primary intermolecular EC1:EC4 and EC2:EC3 interactions. A subset of trans interface residues exhibit isoform-specific conservation, suggesting roles in recognition specificity. Mutation of these residues, along with trans-interacting partner residues, altered the specificities of Pcdh interactions. Together, these data show how sequence variation among Pcdh isoforms encodes their diverse strict homophilic recognition specificities, which are required for their key roles in neural circuit assembly.
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Affiliation(s)
- Kerry Marie Goodman
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Rotem Rubinstein
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Department of Systems Biology, Columbia University, New York, NY 10032, USA
| | - Chan Aye Thu
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Fabiana Bahna
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Seetha Mannepalli
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Göran Ahlsén
- Department of Systems Biology, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA
| | - Chelsea Rittenhouse
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Tom Maniatis
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY 10032, USA
| | - Barry Honig
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Department of Systems Biology, Columbia University, New York, NY 10032, USA; Howard Hughes Medical Institute, Columbia University, New York, NY 10032, USA; Department of Medicine, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY 10032, USA.
| | - Lawrence Shapiro
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA; Department of Systems Biology, Columbia University, New York, NY 10032, USA; Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, NY 10032, USA.
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102
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Molumby MJ, Keeler AB, Weiner JA. Homophilic Protocadherin Cell-Cell Interactions Promote Dendrite Complexity. Cell Rep 2016; 15:1037-1050. [PMID: 27117416 DOI: 10.1016/j.celrep.2016.03.093] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Revised: 02/16/2016] [Accepted: 03/27/2016] [Indexed: 01/04/2023] Open
Abstract
Growth of a properly complex dendrite arbor is a key step in neuronal differentiation and a prerequisite for neural circuit formation. Diverse cell surface molecules, such as the clustered protocadherins (Pcdhs), have long been proposed to regulate circuit formation through specific cell-cell interactions. Here, using transgenic and conditional knockout mice to manipulate γ-Pcdh repertoire in the cerebral cortex, we show that the complexity of a neuron's dendritic arbor is determined by homophilic interactions with other cells. Neurons expressing only one of the 22 γ-Pcdhs can exhibit either exuberant or minimal dendrite complexity, depending only on whether surrounding cells express the same isoform. Furthermore, loss of astrocytic γ-Pcdhs, or disruption of astrocyte-neuron homophilic matching, reduces dendrite complexity cell non-autonomously. Our data indicate that γ-Pcdhs act locally to promote dendrite arborization via homophilic matching, and they confirm that connectivity in vivo depends on molecular interactions between neurons and between neurons and astrocytes.
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Affiliation(s)
- Michael J Molumby
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA; Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA
| | - Austin B Keeler
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA; Graduate Program in Neuroscience, The University of Iowa, Iowa City, IA 52242, USA
| | - Joshua A Weiner
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA; Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA; Graduate Program in Neuroscience, The University of Iowa, Iowa City, IA 52242, USA; Department of Psychiatry, Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA.
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103
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Gendrel AV, Marion-Poll L, Katoh K, Heard E. Random monoallelic expression of genes on autosomes: Parallels with X-chromosome inactivation. Semin Cell Dev Biol 2016; 56:100-110. [PMID: 27101886 DOI: 10.1016/j.semcdb.2016.04.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 04/08/2016] [Accepted: 04/15/2016] [Indexed: 01/04/2023]
Abstract
Genes are generally expressed from their two alleles, except in some particular cases such as random inactivation of one of the two X chromosomes in female mammals or imprinted genes which are expressed only from the maternal or the paternal allele. A lesser-known phenomenon is random monoallelic expression (RME) of autosomal genes, where genes can be stably expressed in a monoallelic manner, from either one of the parental alleles. Studies on autosomal RME face several challenges. First, RME that is based on epigenetic mechanisms has to be distinguished from biased expression of one allele caused by a DNA sequence polymorphism in a regulatory element. Second, RME should not be confused with transient monoallelic expression often observed in single cell analyses, and that often corresponds to dynamic bursting of expression. Thanks to analyses on clonal cell populations, the existence of RME in cultured cells is now well established. Future studies of RME in vivo will have to overcome tissue heterogeneity and certain technical limitations. Here, we discuss current knowledge on autosomal RME, as well as possible mechanisms controlling these expression patterns and potential implications for development and disease, drawing parallels with what is known for X-chromosome inactivation, a paradigm of random monoallelic expression.
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Affiliation(s)
- Anne-Valerie Gendrel
- Institut Curie, PSL Research University, CNRS UMR 3215, INSERM U934, Mammalian Developmental Epigenetics group, F-75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 6, F-75005 Paris, France.
| | - Lucile Marion-Poll
- Institut Curie, PSL Research University, CNRS UMR 3215, INSERM U934, Mammalian Developmental Epigenetics group, F-75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 6, F-75005 Paris, France
| | - Kimiko Katoh
- Institut Curie, PSL Research University, CNRS UMR 3215, INSERM U934, Mammalian Developmental Epigenetics group, F-75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 6, F-75005 Paris, France
| | - Edith Heard
- Institut Curie, PSL Research University, CNRS UMR 3215, INSERM U934, Mammalian Developmental Epigenetics group, F-75005 Paris, France; Sorbonne Universités, UPMC Univ Paris 6, F-75005 Paris, France.
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104
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Hassan BA, Hiesinger PR. Beyond Molecular Codes: Simple Rules to Wire Complex Brains. Cell 2016; 163:285-91. [PMID: 26451480 DOI: 10.1016/j.cell.2015.09.031] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Indexed: 11/30/2022]
Abstract
Molecular codes, like postal zip codes, are generally considered a robust way to ensure the specificity of neuronal target selection. However, a code capable of unambiguously generating complex neural circuits is difficult to conceive. Here, we re-examine the notion of molecular codes in the light of developmental algorithms. We explore how molecules and mechanisms that have been considered part of a code may alternatively implement simple pattern formation rules sufficient to ensure wiring specificity in neural circuits. This analysis delineates a pattern-based framework for circuit construction that may contribute to our understanding of brain wiring.
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Affiliation(s)
- Bassem A Hassan
- Center for the Biology of Disease, VIB, 3000 Leuven, Belgium; Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium.
| | - P Robin Hiesinger
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, 14195 Berlin, Germany; NeuroCure Cluster of Excellence, Charite Universitätsmedizin Berlin, 10117 Berlin, Germany.
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105
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Nicoludis JM, Vogt BE, Green AG, Schärfe CPI, Marks DS, Gaudet R. Antiparallel protocadherin homodimers use distinct affinity- and specificity-mediating regions in cadherin repeats 1-4. eLife 2016; 5:e18449. [PMID: 27472898 PMCID: PMC5001838 DOI: 10.7554/elife.18449] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 07/28/2016] [Indexed: 01/07/2023] Open
Abstract
Protocadherins (Pcdhs) are cell adhesion and signaling proteins used by neurons to develop and maintain neuronal networks, relying on trans homophilic interactions between their extracellular cadherin (EC) repeat domains. We present the structure of the antiparallel EC1-4 homodimer of human PcdhγB3, a member of the γ subfamily of clustered Pcdhs. Structure and sequence comparisons of α, β, and γ clustered Pcdh isoforms illustrate that subfamilies encode specificity in distinct ways through diversification of loop region structure and composition in EC2 and EC3, which contains isoform-specific conservation of primarily polar residues. In contrast, the EC1/EC4 interface comprises hydrophobic interactions that provide non-selective dimerization affinity. Using sequence coevolution analysis, we found evidence for a similar antiparallel EC1-4 interaction in non-clustered Pcdh families. We thus deduce that the EC1-4 antiparallel homodimer is a general interaction strategy that evolved before the divergence of these distinct protocadherin families.
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Affiliation(s)
- John M Nicoludis
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States,Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Bennett E Vogt
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Anna G Green
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - Charlotta PI Schärfe
- Department of Systems Biology, Harvard Medical School, Boston, United States,Applied Bioinformatics, Department of Computer Science, University of Tübingen, Tübingen, Germany
| | - Debora S Marks
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States,
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106
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Shonubi A, Roman C, Phillips GR. The clustered protocadherin endolysosomal trafficking motif mediates cytoplasmic association. BMC Cell Biol 2015; 16:28. [PMID: 26608278 PMCID: PMC4660814 DOI: 10.1186/s12860-015-0074-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2015] [Accepted: 11/12/2015] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Clustered protocadherins (Pcdhs) are a large family of neural cadherin-like proteins encoded by individual exons located within three gene clusters. Each exon codes an extracellular, transmembrane, and proximal cytoplasmic domain. These "variable" regions may be spliced to a constant cytoplasmic moiety encoded at the end of a cluster. Pcdh extracellular domains mediate homophilic cell-cell binding but their cytoplasmic domains cause intracellular retention and may negatively regulate Pcdh cell-cell binding. Pcdhs can be found at the cell surface in neurons and other cells but are also, unlike classical cadherins, prominently trafficked to the endolysosome system. It was previously found that a segment within the variable portion of the Pcdh-γA3 cytoplasmic domain (VCD) was shown to be necessary for endolysosomal trafficking. RESULTS Here it is shown that this same VCD segment can mediate cytoplasmic association among Pcdhs from the different clusters. Internal deletions within this VCD region (termed here the VCD motif) that disrupt the association altered trafficking of Pcdh-γA3 in the endolysosomal system while deletions outside VCD motif did not affect trafficking. CONCLUSIONS The results show that Pcdhs associate cytoplasmically via a motif within the VCD and that this is critical for Pcdh trafficking. Given that truncation at the VCD motif alters endolysosomal trafficking of Pcdhs, the VCD interaction described here may provide new insights into the dynamic nature of Pcdh mediated cell-cell interactions.
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Affiliation(s)
- Adam Shonubi
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY, 10314, USA.
| | - Chantelle Roman
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY, 10314, USA.
| | - Greg R Phillips
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY, 10314, USA. .,Center for Developmental Neuroscience, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY, 10314, USA. .,CUNY Graduate Center, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY, 10314, USA.
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107
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Nicoludis JM, Lau SY, Schärfe CPI, Marks DS, Weihofen WA, Gaudet R. Structure and Sequence Analyses of Clustered Protocadherins Reveal Antiparallel Interactions that Mediate Homophilic Specificity. Structure 2015; 23:2087-98. [PMID: 26481813 PMCID: PMC4635037 DOI: 10.1016/j.str.2015.09.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 09/14/2015] [Accepted: 09/15/2015] [Indexed: 01/07/2023]
Abstract
Clustered protocadherin (Pcdh) proteins mediate dendritic self-avoidance in neurons via specific homophilic interactions in their extracellular cadherin (EC) domains. We determined crystal structures of EC1-EC3, containing the homophilic specificity-determining region, of two mouse clustered Pcdh isoforms (PcdhγA1 and PcdhγC3) to investigate the nature of the homophilic interaction. Within the crystal lattices, we observe antiparallel interfaces consistent with a role in trans cell-cell contact. Antiparallel dimerization is supported by evolutionary correlations. Two interfaces, located primarily on EC2-EC3, involve distinctive clustered Pcdh structure and sequence motifs, lack predicted glycosylation sites, and contain residues highly conserved in orthologs but not paralogs, pointing toward their biological significance as homophilic interaction interfaces. These two interfaces are similar yet distinct, reflecting a possible difference in interaction architecture between clustered Pcdh subfamilies. These structures initiate a molecular understanding of clustered Pcdh assemblies that are required to produce functional neuronal networks.
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Affiliation(s)
- John M. Nicoludis
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA, 02138, USA
| | - Sze-Yi Lau
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA, 02138, USA
| | - Charlotta P. I. Schärfe
- Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA,Applied Bioinformatics, Department of Computer Science, University of Tübingen, Tübingen, Germany
| | - Debora S. Marks
- Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA
| | - Wilhelm A. Weihofen
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA, 02138, USA,Correspondence: (R. G.), (W. A.W.)
| | - Rachelle Gaudet
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA, 02138, USA,Correspondence: (R. G.), (W. A.W.)
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108
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Abstract
The nervous system is populated by numerous types of neurons, each bearing a dendritic arbor with a characteristic morphology. These type-specific features influence many aspects of a neuron's function, including the number and identity of presynaptic inputs and how inputs are integrated to determine firing properties. Here, we review the mechanisms that regulate the construction of cell type-specific dendrite patterns during development. We focus on four aspects of dendrite patterning that are particularly important in determining the function of the mature neuron: (a) dendrite shape, including branching pattern and geometry of the arbor; (b) dendritic arbor size;
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Affiliation(s)
| | - Joshua R Sanes
- Center for Brain Science and Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138;
| | - Jeremy N Kay
- Departments of Neurobiology and Ophthalmology, Duke University School of Medicine, Durham, North Carolina 27710;
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109
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Garrett AM, Burgess RW. Self-awareness in the retina. eLife 2015; 4. [PMID: 26305501 PMCID: PMC4548409 DOI: 10.7554/elife.10233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Proteins called gamma-protocadherins are essential for the establishment of working circuits of neurons in the retina.
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