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Traenkner D, Shennib O, Johnson A, Weinbrom A, Taylor MR, Williams ME. Modular Splicing Is Linked to Evolution in the Synapse-Specificity Molecule Kirrel3. eNeuro 2023; 10:ENEURO.0253-23.2023. [PMID: 37977826 DOI: 10.1523/eneuro.0253-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 11/09/2023] [Accepted: 11/13/2023] [Indexed: 11/19/2023] Open
Abstract
Kirrel3 is a cell-adhesion molecule that instructs the formation of specific synapses during brain development in mouse and Kirrel3 variants may be risk factors for autism and intellectual disabilities in humans. Kirrel3 is predicted to undergo alternative splicing but brain isoforms have not been studied. Here, we present the first in-depth characterization of Kirrel3 isoform diversity in brain using targeted, long-read mRNA sequencing of mouse hippocampus. We identified 19 isoforms with predicted transmembrane and secreted forms and show that even rare isoforms generate detectable protein in the brain. We also analyzed publicly-available long-read mRNA databases from human brain tissue and found 11 Kirrel3 isoforms that, similar to mouse, encode transmembrane and secreted forms. In mice and humans, Kirrel3 diversity arises from alternative, independent use of protein-domain coding exons and alternative early translation-stop signals. Intriguingly, the alternatively spliced exons appear at branch points in the chordate phylogenetic tree, including one exon only found in humans and their closest living relatives, the great apes. Together, these results validate a simple pipeline for analyzing isoform diversity in genes with low expression and suggest that Kirrel3 function is fine-tuned by alternative splicing and may play a role in brain evolution.
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Affiliation(s)
- Dimitri Traenkner
- Department of Neurobiology, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Omar Shennib
- Department of Neurobiology, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Alyssa Johnson
- Department of Neurobiology, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Adam Weinbrom
- Department of Neurobiology, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Matthew R Taylor
- Department of Neurobiology, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Megan E Williams
- Department of Neurobiology, University of Utah, School of Medicine, Salt Lake City, UT 84112
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Wang J, Vaddadi N, Pak JS, Park Y, Quilez S, Roman CA, Dumontier E, Thornton JW, Cloutier JF, Özkan E. Molecular and structural basis of olfactory sensory neuron axon coalescence by Kirrel receptors. Cell Rep 2021; 37:109940. [PMID: 34731636 PMCID: PMC8628261 DOI: 10.1016/j.celrep.2021.109940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 07/30/2021] [Accepted: 10/13/2021] [Indexed: 01/21/2023] Open
Abstract
Projections from sensory neurons of olfactory systems coalesce into glomeruli in the brain. The Kirrel receptors are believed to homodimerize via their ectodomains and help separate sensory neuron axons into Kirrel2- or Kirrel3-expressing glomeruli. Here, we present the crystal structures of homodimeric Kirrel receptors and show that the closely related Kirrel2 and Kirrel3 have evolved specific sets of polar and hydrophobic interactions, respectively, disallowing heterodimerization while preserving homodimerization, likely resulting in proper segregation and coalescence of Kirrel-expressing axons into glomeruli. We show that the dimerization interface at the N-terminal immunoglobulin (IG) domains is necessary and sufficient to create homodimers and fail to find evidence for a secondary interaction site in Kirrel ectodomains. Furthermore, we show that abolishing dimerization of Kirrel3 in vivo leads to improper formation of glomeruli in the mouse accessory olfactory bulb as observed in Kirrel3-/- animals. Our results provide evidence for Kirrel3 homodimerization controlling axonal coalescence.
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Affiliation(s)
- Jing Wang
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Neelima Vaddadi
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada
| | - Joseph S Pak
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA
| | - Yeonwoo Park
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Sabrina Quilez
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada
| | - Christina A Roman
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA
| | - Emilie Dumontier
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada
| | - Joseph W Thornton
- Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL 60637, USA; Department of Human Genetics, The University of Chicago, Chicago, IL 60637, USA; Department of Ecology and Evolution, The University of Chicago, Chicago, IL 60637, USA
| | - Jean-François Cloutier
- The Neuro-Montreal Neurological Institute and Hospital, McGill University, Montréal, QC H3A 2B4, Canada; Department of Neurology and Neurosurgery, McGill University, Montréal, QC H3A 2B4, Canada; Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada.
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA; Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, The University of Chicago, Chicago, IL 60637, USA.
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Vaddadi N, Iversen K, Raja R, Phen A, Brignall A, Dumontier E, Cloutier JF. Kirrel2 is differentially required in populations of olfactory sensory neurons for the targeting of axons in the olfactory bulb. Development 2019; 146:dev.173310. [PMID: 31142543 DOI: 10.1242/dev.173310] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 05/15/2019] [Indexed: 01/25/2023]
Abstract
The formation of olfactory maps in the olfactory bulb (OB) is crucial for the control of innate and learned mouse behaviors. Olfactory sensory neurons (OSNs) expressing a specific odorant receptor project axons into spatially conserved glomeruli within the OB and synapse onto mitral cell dendrites. Combinatorial expression of members of the Kirrel family of cell adhesion molecules has been proposed to regulate OSN axonal coalescence; however, loss-of-function experiments have yet to establish their requirement in this process. We examined projections of several OSN populations in mice that lacked either Kirrel2 alone, or both Kirrel2 and Kirrel3. Our results show that Kirrel2 and Kirrel3 are dispensable for the coalescence of MOR1-3-expressing OSN axons to the most dorsal region (DI) of the OB. In contrast, loss of Kirrel2 caused MOR174-9- and M72-expressing OSN axons, projecting to the DII region, to target ectopic glomeruli. Our loss-of-function approach demonstrates that Kirrel2 is required for axonal coalescence in subsets of OSNs that project axons to the DII region and reveals that Kirrel2/3-independent mechanisms also control OSN axonal coalescence in certain regions of the OB.
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Affiliation(s)
- Neelima Vaddadi
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada
| | - Katrine Iversen
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada
| | - Reesha Raja
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada
| | - Alina Phen
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada
| | - Alexandra Brignall
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada
| | - Emilie Dumontier
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada
| | - Jean-François Cloutier
- Montreal Neurological Institute, Centre for Neuronal Survival, 3801 University, Montréal, Québec H3A 2B4, Canada .,Department of Neurology and Neurosurgery, McGill University, Montréal, Québec H3A 2B4, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3A 0C7, Canada
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Martin EA, Woodruff D, Rawson RL, Williams ME. Examining Hippocampal Mossy Fiber Synapses by 3D Electron Microscopy in Wildtype and Kirrel3 Knockout Mice. eNeuro 2017; 4:ENEURO. [PMID: 28670619 DOI: 10.1523/ENEURO.0088-17.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2017] [Revised: 04/20/2017] [Accepted: 05/17/2017] [Indexed: 11/27/2022] Open
Abstract
Neural circuits balance excitatory and inhibitory activity and disruptions in this balance are commonly found in neurodevelopmental disorders. Mice lacking the intellectual disability and autism-associated gene Kirrel3 have an excitation-inhibition imbalance in the hippocampus but the precise synaptic changes underlying this functional defect are unknown. Kirrel3 is a homophilic adhesion molecule expressed in dentate gyrus (DG) and GABA neurons. It was suggested that the excitation-inhibition imbalance of hippocampal neurons in Kirrel3 knockout mice is due to loss of mossy fiber (MF) filopodia, which are DG axon protrusions thought to excite GABA neurons and thereby provide feed-forward inhibition to CA3 pyramidal neurons. Fewer filopodial structures were observed in Kirrel3 knockout mice but neither filopodial synapses nor DG en passant synapses, which also excite GABA neurons, were examined. Here, we used serial block-face scanning electron microscopy (SBEM) with 3D reconstruction to define the precise connectivity of MF filopodia and elucidate synaptic changes induced by Kirrel3 loss. Surprisingly, we discovered wildtype MF filopodia do not synapse exclusively onto GABA neurons as previously thought, but instead synapse with similar frequency onto GABA neurons and CA3 neurons. Moreover, Kirrel3 loss selectively reduces MF filopodial synapses onto GABA neurons but not those made onto CA3 neurons or en passant synapses. In sum, the selective loss of MF filopodial synapses with GABA neurons likely underlies the hippocampal activity imbalance observed in Kirrel3 knockout mice and may impact neural function in patients with Kirrel3-dependent neurodevelopmental disorders.
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Roh JD, Choi SY, Cho YS, Choi TY, Park JS, Cutforth T, Chung W, Park H, Lee D, Kim MH, Lee Y, Mo S, Rhee JS, Kim H, Ko J, Choi SY, Bae YC, Shen K, Kim E, Han K. Increased Excitatory Synaptic Transmission of Dentate Granule Neurons in Mice Lacking PSD-95-Interacting Adhesion Molecule Neph2/ Kirrel3 during the Early Postnatal Period. Front Mol Neurosci 2017; 10:81. [PMID: 28381988 PMCID: PMC5360738 DOI: 10.3389/fnmol.2017.00081] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Accepted: 03/08/2017] [Indexed: 11/13/2022] Open
Abstract
Copy number variants and point mutations of NEPH2 (also called KIRREL3) gene encoding an immunoglobulin (Ig) superfamily adhesion molecule have been linked to autism spectrum disorders, intellectual disability and neurocognitive delay associated with Jacobsen syndrome, but the physiological roles of Neph2 in the mammalian brain remain largely unknown. Neph2 is highly expressed in the dentate granule (DG) neurons of the hippocampus and is localized in both dendrites and axons. It was recently shown that Neph2 is required for the formation of mossy fiber filopodia, the axon terminal structure of DG neurons forming synapses with GABAergic neurons of CA3. In contrast, however, it is unknown whether Neph2 also has any roles in the postsynaptic compartments of DG neurons. We here report that, through its C-terminal PDZ domain-binding motif, Neph2 directly interacts with postsynaptic density (PSD)-95, an abundant excitatory postsynaptic scaffolding protein. Moreover, Neph2 protein is detected in the brain PSD fraction and interacts with PSD-95 in synaptosomal lysates. Functionally, loss of Neph2 in mice leads to age-specific defects in the synaptic connectivity of DG neurons. Specifically, Neph2-/- mice show significantly increased spontaneous excitatory synaptic events in DG neurons at postnatal week 2 when the endogenous Neph2 protein expression peaks, but show normal excitatory synaptic transmission at postnatal week 3. The evoked excitatory synaptic transmission and synaptic plasticity of medial perforant pathway (MPP)-DG synapses are also normal in Neph2-/- mice at postnatal week 3, further confirming the age-specific synaptic defects. Together, our results provide some evidence for the postsynaptic function of Neph2 in DG neurons during the early postnatal period, which might be implicated in neurodevelopmental and cognitive disorders caused by NEPH2 mutations.
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Affiliation(s)
- Junyeop D Roh
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST) Daejeon, South Korea
| | - Su-Yeon Choi
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS) Daejeon, South Korea
| | - Yi Sul Cho
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University Daegu, South Korea
| | - Tae-Yong Choi
- Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry Seoul, South Korea
| | - Jong-Sil Park
- Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry Seoul, South Korea
| | - Tyler Cutforth
- Department of Neurology, Columbia University Medical Center New York, NY, USA
| | - Woosuk Chung
- Department of Anesthesiology and Pain Medicine, College of Medicine, Chungnam National University Daejeon, South Korea
| | - Hanwool Park
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS) Daejeon, South Korea
| | - Dongsoo Lee
- Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS) Daejeon, South Korea
| | - Myeong-Heui Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST) Daejeon, South Korea
| | - Yeunkum Lee
- Department of Neuroscience, College of Medicine, Korea University Seoul, South Korea
| | - Seojung Mo
- Department of Anatomy, College of Medicine, Korea University Seoul, South Korea
| | - Jeong-Seop Rhee
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine Göttingen, Germany
| | - Hyun Kim
- Department of Anatomy, College of Medicine, Korea University Seoul, South Korea
| | - Jaewon Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST) Daegu, South Korea
| | - Se-Young Choi
- Department of Physiology, Dental Research Institute, Seoul National University School of Dentistry Seoul, South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University Daegu, South Korea
| | - Kang Shen
- Department of Biology, Howard Hughes Medical Institute, Stanford University Stanford, CA, USA
| | - Eunjoon Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology (KAIST)Daejeon, South Korea; Center for Synaptic Brain Dysfunctions, Institute for Basic Science (IBS)Daejeon, South Korea
| | - Kihoon Han
- Department of Neuroscience, College of Medicine, Korea University Seoul, South Korea
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Martin EA, Muralidhar S, Wang Z, Cervantes DC, Basu R, Taylor MR, Hunter J, Cutforth T, Wilke SA, Ghosh A, Williams ME. The intellectual disability gene Kirrel3 regulates target-specific mossy fiber synapse development in the hippocampus. eLife 2015; 4:e09395. [PMID: 26575286 PMCID: PMC4642954 DOI: 10.7554/elife.09395] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 10/13/2015] [Indexed: 12/14/2022] Open
Abstract
Synaptic target specificity, whereby neurons make distinct types of synapses with different target cells, is critical for brain function, yet the mechanisms driving it are poorly understood. In this study, we demonstrate Kirrel3 regulates target-specific synapse formation at hippocampal mossy fiber (MF) synapses, which connect dentate granule (DG) neurons to both CA3 and GABAergic neurons. Here, we show Kirrel3 is required for formation of MF filopodia; the structures that give rise to DG-GABA synapses and that regulate feed-forward inhibition of CA3 neurons. Consequently, loss of Kirrel3 robustly increases CA3 neuron activity in developing mice. Alterations in the Kirrel3 gene are repeatedly associated with intellectual disabilities, but the role of Kirrel3 at synapses remained largely unknown. Our findings demonstrate that subtle synaptic changes during development impact circuit function and provide the first insight toward understanding the cellular basis of Kirrel3-dependent neurodevelopmental disorders. DOI:http://dx.doi.org/10.7554/eLife.09395.001 Nerve cells in the brain connect to each other via junctions called synapses to form vast networks that process information. Much like streets can be joined with stop signs, traffic lights, or exit ramps depending on the flow of traffic, different types of synapses control the flow of information along nerves in distinct ways. In a region of the brain called the hippocampus, nerve cells called DG neurons are connected to other neurons by two different types of synapses. One type of synapse allows the DG neurons to activate CA3 neurons, while the second type allows the DG neurons to activate GABAergic neurons. These same GABAergic neurons can then inhibit the activity of the CA3 neurons. Therefore, through these two different types of synapses, DG neurons can both increase and decrease the activity of the CA3 neurons. This delicate balance of activity across the two types of DG synapses is very important for the hippocampus to work properly, which is critical for our ability to learn and remember. Mutations in the gene that encodes a protein called Kirrel3 are associated with autism, Jacobsen's syndrome, and other disorders that affect intellectual ability in humans. Kirrel3 is similar to a protein found in roundworms that regulates the formation of synapses, but it is not known if it plays the same role in humans and other mammals. Now, Martin, Muralidhar et al. studied the role of Kirrel3 in mice. The experiments show that Kirrel3 is produced in both the DG neurons and the GABAergic neurons, but not the CA3 neurons. Young mutant mice that lacked Kirrel3 made fewer synapse-forming structures between DG neurons and GABAergic neurons than normal mice, but the synapses that connect DG neurons to CA3 neurons formed normally. This disrupted the balance of activity across the two types of DG synapses and the CA3 neurons in the mutant mice were over-active. Together, Martin, Muralidhar et al.'s findings show that altering the levels of Kirrel3 can alter the balance of synapses in the hippocampus. This may explain how even very small changes in synapse formation during brain development can have a big impact on nerve cell activity. The next challenge is to understand exactly how Kirrel3 helps build synapses, which may lead to the development of new drugs that help to rebalance brain activity in people that lack Kirrel3. DOI:http://dx.doi.org/10.7554/eLife.09395.002
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Affiliation(s)
- E Anne Martin
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Shruti Muralidhar
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Zhirong Wang
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Diégo Cordero Cervantes
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Raunak Basu
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Matthew R Taylor
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Jennifer Hunter
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
| | - Tyler Cutforth
- Department of Neurology, Columbia University, New York City, United States
| | - Scott A Wilke
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, San Diego, United States
| | - Anirvan Ghosh
- Neuroscience Discovery, Roche Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Megan E Williams
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, United States
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