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Cheah M, Cheng Y, Petrova V, Cimpean A, Jendelova P, Swarup V, Woolf CJ, Geschwind DH, Fawcett JW. Integrin-Driven Axon Regeneration in the Spinal Cord Activates a Distinctive CNS Regeneration Program. J Neurosci 2023; 43:4775-4794. [PMID: 37277179 PMCID: PMC10312060 DOI: 10.1523/jneurosci.2076-22.2023] [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] [Received: 11/06/2022] [Revised: 04/19/2023] [Accepted: 04/21/2023] [Indexed: 06/07/2023] Open
Abstract
The peripheral branch of sensory dorsal root ganglion (DRG) neurons regenerates readily after injury unlike their central branch in the spinal cord. However, extensive regeneration and reconnection of sensory axons in the spinal cord can be driven by the expression of α9 integrin and its activator kindlin-1 (α9k1), which enable axons to interact with tenascin-C. To elucidate the mechanisms and downstream pathways affected by activated integrin expression and central regeneration, we conducted transcriptomic analyses of adult male rat DRG sensory neurons transduced with α9k1, and controls, with and without axotomy of the central branch. Expression of α9k1 without the central axotomy led to upregulation of a known PNS regeneration program, including many genes associated with peripheral nerve regeneration. Coupling α9k1 treatment with dorsal root axotomy led to extensive central axonal regeneration. In addition to the program upregulated by α9k1 expression, regeneration in the spinal cord led to expression of a distinctive CNS regeneration program, including genes associated with ubiquitination, autophagy, endoplasmic reticulum (ER), trafficking, and signaling. Pharmacological inhibition of these processes blocked the regeneration of axons from DRGs and human iPSC-derived sensory neurons, validating their causal contributions to sensory regeneration. This CNS regeneration-associated program showed little correlation with either embryonic development or PNS regeneration programs. Potential transcriptional drivers of this CNS program coupled to regeneration include Mef2a, Runx3, E2f4, and Yy1. Signaling from integrins primes sensory neurons for regeneration, but their axon growth in the CNS is associated with an additional distinctive program that differs from that involved in PNS regeneration.SIGNIFICANCE STATEMENT Restoration of neurologic function after spinal cord injury has yet to be achieved in human patients. To accomplish this, severed nerve fibers must be made to regenerate. Reconstruction of nerve pathways has not been possible, but recently, a method for stimulating long-distance axon regeneration of sensory fibers in rodents has been developed. This research uses profiling of messenger RNAs in the regenerating sensory neurons to discover which mechanisms are activated. This study shows that the regenerating neurons initiate a novel CNS regeneration program which includes molecular transport, autophagy, ubiquitination, and modulation of the endoplasmic reticulum (ER). The study identifies mechanisms that neurons need to activate to regenerate their nerve fibers.
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Affiliation(s)
- Menghon Cheah
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0PY, United Kingdom
| | - Yuyan Cheng
- Program in Neurogenetics, Department of Neurology, and Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - Veselina Petrova
- Department of Neurobiology, Harvard Medical School; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Anda Cimpean
- Centre for Reconstructive Neuroscience, Institute of Experimental Medicine Czech Academy of Science, Prague, Czech Republic
| | - Pavla Jendelova
- Centre for Reconstructive Neuroscience, Institute of Experimental Medicine Czech Academy of Science, Prague, Czech Republic
| | - Vivek Swarup
- Program in Neurogenetics, Department of Neurology, and Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095
- Department of Neurobiology and Behavior, University of California, Irvine, California 92697
| | - Clifford J Woolf
- Department of Neurobiology, Harvard Medical School; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, Massachusetts 02115
| | - Daniel H Geschwind
- Program in Neurogenetics, Department of Neurology, and Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California 90095
| | - James W Fawcett
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0PY, United Kingdom
- Centre for Reconstructive Neuroscience, Institute of Experimental Medicine Czech Academy of Science, Prague, Czech Republic
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Thapa I, Vahrenkamp R, Witus SR, Lightle C, Falkenberg O, Sellin Jeffries M, Klevit R, Stewart MD. Conservation of transcriptional regulation by BRCA1 and BARD1 in Caenorhabditis elegans. Nucleic Acids Res 2023; 51:2108-2116. [PMID: 36250637 PMCID: PMC10018340 DOI: 10.1093/nar/gkac877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/22/2022] [Accepted: 09/29/2022] [Indexed: 01/27/2023] Open
Abstract
The tumor-suppressor proteins BRCA1 and BARD1 function as an E3 ubiquitin ligase to facilitate transcriptional repression and DNA damage repair. This is mediated in-part through its ability to mono-ubiquitylate histone H2A in nucleosomes. Studies in Caenorhabditis elegans have been used to elucidate numerous functions of BRCA1 and BARD1; however, it has not been established that the C. elegans orthologs, BRC-1 and BRD-1, retain all the functions of their human counterparts. Here we explore the conservation of enzymatic activity toward nucleosomes which leads to repression of estrogen-metabolizing cytochrome P450 (cyp) genes in humans. Biochemical assays establish that BRC-1 and BRD-1 contribute to ubiquitylation of histone H2A in the nucleosome. Mutational analysis shows that while BRC-1 likely binds the nucleosome using a conserved interface, BRD-1 and BARD1 have evolved different modes of binding, resulting in a difference in the placement of ubiquitin on H2A. Gene expression analysis reveals that in spite of this difference, BRC-1 and BRD-1 also contribute to cyp gene repression in C. elegans. Establishing conservation of these functions in C. elegans allows for use of this powerful model organism to address remaining questions regarding regulation of gene expression by BRCA1 and BARD1.
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Affiliation(s)
| | | | - Samuel R Witus
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Caitlin Lightle
- Department of Biology, Texas Christian University, Fort Worth, TX 76129, USA
| | - Owen Falkenberg
- Department of Biology, Texas Christian University, Fort Worth, TX 76129, USA
| | | | - Rachel E Klevit
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
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Li Q, Kaur A, Okada K, McKenney RJ, Engebrecht J. Differential requirement for BRCA1-BARD1 E3 ubiquitin ligase activity in DNA damage repair and meiosis in the Caenorhabditis elegans germ line. PLoS Genet 2023; 19:e1010457. [PMID: 36716349 PMCID: PMC9910797 DOI: 10.1371/journal.pgen.1010457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 02/09/2023] [Accepted: 01/19/2023] [Indexed: 02/01/2023] Open
Abstract
The tumor suppressor BRCA1-BARD1 complex regulates many cellular processes; of critical importance to its tumor suppressor function is its role in genome integrity. Although RING E3 ubiquitin ligase activity is the only known enzymatic activity of the complex, the in vivo requirement for BRCA1-BARD1 E3 ubiquitin ligase activity has been controversial. Here we probe the role of BRCA1-BARD1 E3 ubiquitin ligase activity in vivo using C. elegans. Genetic, cell biological, and biochemical analyses of mutants defective for E3 ligase activity suggest there is both E3 ligase-dependent and independent functions of the complex in the context of DNA damage repair and meiosis. We show that E3 ligase activity is important for nuclear accumulation of the complex and specifically to concentrate at meiotic recombination sites but not at DNA damage sites in proliferating germ cells. While BRCA1 alone is capable of monoubiquitylation, BARD1 is required with BRCA1 to promote polyubiquitylation. We find that the requirement for E3 ligase activity and BARD1 in DNA damage signaling and repair can be partially alleviated by driving the nuclear accumulation and self-association of BRCA1. Our data suggest that in addition to E3 ligase activity, BRCA1 may serve a structural role for DNA damage signaling and repair while BARD1 plays an accessory role to enhance BRCA1 function.
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Affiliation(s)
- Qianyan Li
- Department of Molecular and Cellular Biology, University of California Davis, Davis, California, United States of America
- Biochemistry, Molecular, Cellular and Developmental Biology Graduate Group, University of California Davis, Davis, California, United States of America
| | - Arshdeep Kaur
- Department of Molecular and Cellular Biology, University of California Davis, Davis, California, United States of America
| | - Kyoko Okada
- Department of Molecular and Cellular Biology, University of California Davis, Davis, California, United States of America
| | - Richard J. McKenney
- Department of Molecular and Cellular Biology, University of California Davis, Davis, California, United States of America
- Biochemistry, Molecular, Cellular and Developmental Biology Graduate Group, University of California Davis, Davis, California, United States of America
| | - JoAnne Engebrecht
- Department of Molecular and Cellular Biology, University of California Davis, Davis, California, United States of America
- Biochemistry, Molecular, Cellular and Developmental Biology Graduate Group, University of California Davis, Davis, California, United States of America
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CDK14 Promotes Axon Regeneration by Regulating the Noncanonical Wnt Signaling Pathway in a Kinase-Independent Manner. J Neurosci 2021; 41:8309-8320. [PMID: 34429379 PMCID: PMC8496196 DOI: 10.1523/jneurosci.0711-21.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Revised: 08/05/2021] [Accepted: 08/10/2021] [Indexed: 01/13/2023] Open
Abstract
The postinjury regenerative capacity of neurons is known to be mediated by a complex interaction of intrinsic regenerative pathways and external cues. In Caenorhabditis elegans, the initiation of axon regeneration is regulated by the nonmuscle myosin light chain-4 (MLC-4) phosphorylation signaling pathway. In this study, we have identified svh-16/cdk-14, a mammalian CDK14 homolog, as a positive regulator of axon regeneration in motor neurons. We then isolated the CDK-14-binding protein MIG-5/Disheveled (Dsh) and found that EGL-20/Wnt and the MIG-1/Frizzled receptor (Fz) are required for efficient axon regeneration. Further, we demonstrate that CDK-14 activates EPHX-1, the C. elegans homolog of the mammalian ephexin Rho-type GTPase guanine nucleotide exchange factor (GEF), in a kinase-independent manner. EPHX-1 functions as a GEF for the CDC-42 GTPase, inhibiting myosin phosphatase, which maintains MLC-4 phosphorylation. These results suggest that CDK14 activates the RhoGEF–CDC42–MLC phosphorylation axis in a noncanonical Wnt signaling pathway that promotes axon regeneration. SIGNIFICANCE STATEMENT Noncanonical Wnt signaling is mediated by Frizzled receptor (Fz), Disheveled (Dsh), Rho-type GTPase, and nonmuscle myosin light chain (MLC) phosphorylation. This study identified svh-16/cdk-14, which encodes a mammalian CDK14 homolog, as a regulator of axon regeneration in Caenorhabditis elegans motor neurons. We show that CDK-14 binds to MIG-5/Dsh, and that EGL-20/Wnt, MIG-1/Fz, and EPHX-1/RhoGEF are required for axon regeneration. The phosphorylation-mimetic MLC-4 suppressed axon regeneration defects in mig-1, cdk-14, and ephx-1 mutants. CDK-14 mediates kinase-independent activation of EPHX-1, which functions as a guanine nucleotide exchange factor for CDC-42 GTPase. Activated CDC-42 inactivates myosin phosphatase and thereby maintains MLC phosphorylation. Thus, the noncanonical Wnt signaling pathway controls axon regeneration via the CDK-14–EPHX-1–CDC-42–MLC phosphorylation axis.
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