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Chinnaiya K, Placzek M. A Methodology for the Enzymatic Isolation of Embryonic Hypothalamus Tissue and Its Acute or Post-Culture Analysis by Multiplex Hybridisation Chain Reaction. Bio Protoc 2023; 13:e4898. [PMID: 38125731 PMCID: PMC10730952 DOI: 10.21769/bioprotoc.4898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 09/27/2023] [Accepted: 10/16/2023] [Indexed: 12/23/2023] Open
Abstract
The hypothalamus is an evolutionarily ancient part of the vertebrate ventral forebrain that integrates the dialogue between environment, peripheral body, and brain to centrally govern an array of physiologies and behaviours. Characterizing the mechanisms that control hypothalamic development illuminates both hypothalamic organization and function. Critical to the ability to unravel such mechanisms is the skill to isolate hypothalamic tissue, enabling both its acute analysis and its analysis after explant and culture. Tissue explants, in which cells develop in a manner analogous to their in vivo counterparts, are a highly effective tool to investigate the extrinsic signals and tissue-intrinsic self-organising features that drive hypothalamic development. The hypothalamus, however, is induced and patterned at neural tube stages of development, when the tissue is difficult to isolate, and its resident cells complex to define. No single molecular marker distinguishes early hypothalamic progenitor subsets from other cell types in the neural tube, and so their accurate dissection requires the simultaneous analysis of multiple proteins or mRNAs, techniques that were previously limited by antibody availability or were arduous to perform. Here, we overcome these challenges. We describe methodologies to precisely isolate early hypothalamic tissue from the embryonic chick at three distinct patterning stages and to culture hypothalamic explants in three-dimensional gels. We then describe optimised protocols for the analysis of embryos, isolated embryonic tissue, or cultured hypothalamic explants by multiplex hybridisation chain reaction. These methods can be applied to other vertebrates, including mouse, and to other tissue types. Key features • Detailed protocols for enzymatic isolation of embryonic chick hypothalamus at three patterning stages; methods can be extended to other vertebrates and tissues. • Brief methodologies for three-dimensional culture of hypothalamic tissue explants. • Optimised protocols for multiplex hybridisation chain reaction for analysis of embryos, isolated embryonic tissues, or explants.
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Affiliation(s)
| | - Marysia Placzek
- School of Biosciences, University of Sheffield, Sheffield, UK
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Zhuang M, Li X, Zhu J, Zhang J, Niu F, Liang F, Chen M, Li D, Han P, Ji SJ. The m6A reader YTHDF1 regulates axon guidance through translational control of Robo3.1 expression. Nucleic Acids Res 2019; 47:4765-4777. [PMID: 30843071 PMCID: PMC6511866 DOI: 10.1093/nar/gkz157] [Citation(s) in RCA: 128] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 02/25/2019] [Accepted: 02/27/2019] [Indexed: 12/02/2022] Open
Abstract
N 6-Methyladenosine (m6A) is a dynamic mRNA modification which regulates protein expression in various posttranscriptional levels. Functional studies of m6A in nervous system have focused on its writers and erasers so far, whether and how m6A readers mediate m6A functions through recognizing and binding their target mRNA remains poorly understood. Here, we find that the expression of axon guidance receptor Robo3.1 which plays important roles in midline crossing of spinal commissural axons is regulated precisely at translational level. The m6A reader YTHDF1 binds to and positively regulates translation of m6A-modified Robo3.1 mRNA. Either mutation of m6A sites in Robo3.1 mRNA or YTHDF1 knockdown or knockout leads to dramatic reduction of Robo3.1 protein without affecting Robo3.1 mRNA level. Specific ablation of Ythdf1 in spinal commissural neurons results in pre-crossing axon guidance defects. Our findings identify a mechanism that YTHDF1-mediated translation of m6A-modified Robo3.1 mRNA controls pre-crossing axon guidance in spinal cord.
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Affiliation(s)
- Mengru Zhuang
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
- SUSTech-HKUST Joint PhD Program, Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
| | - Xinbei Li
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Junda Zhu
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Jian Zhang
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Fugui Niu
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
- SUSTech-HIT Joint Graduate Program, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Fanghao Liang
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
- SUSTech-HIT Joint Graduate Program, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Mengxian Chen
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Duo Li
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Peng Han
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
| | - Sheng-Jian Ji
- Department of Biology, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
- Institute of Neuroscience, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
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Rappaz B, Lai Wing Sun K, Correia JP, Wiseman PW, Kennedy TE. FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones. PLoS One 2016; 11:e0159405. [PMID: 27482713 PMCID: PMC4970703 DOI: 10.1371/journal.pone.0159405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/02/2016] [Indexed: 12/29/2022] Open
Abstract
Netrin-1 is an essential extracellular chemoattractant that signals through its receptor DCC to guide commissural axon extension in the embryonic spinal cord. DCC directs the organization of F-actin in growth cones by activating an intracellular protein complex that includes the Rho GTPase Cdc42, a critical regulator of cell polarity and directional migration. To address the spatial distribution of signaling events downstream of netrin-1, we expressed the FRET biosensor Raichu-Cdc42 in cultured embryonic rat spinal commissural neurons. Using FLIM-FRET imaging we detected rapid activation of Cdc42 in neuronal growth cones following application of netrin-1. Investigating the signaling mechanisms that control Cdc42 activation by netrin-1, we demonstrate that netrin-1 rapidly enriches DCC at the leading edge of commissural neuron growth cones and that netrin-1 induced activation of Cdc42 in the growth cone is blocked by inhibiting src family kinase signaling. These findings reveal the activation of Cdc42 in embryonic spinal commissural axon growth cones and support the conclusion that src family kinase activation downstream of DCC is required for Cdc42 activation by netrin-1.
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Affiliation(s)
- Benjamin Rappaz
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Karen Lai Wing Sun
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - James P. Correia
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Paul W. Wiseman
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
- Department of Chemistry, McGill University, Montreal, QC, H3A 0B8, Canada
| | - Timothy E. Kennedy
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
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Chen X, Yang H, Zhou X, Zhang L, Lu X. MiR-93 Targeting EphA4 Promotes Neurite Outgrowth from Spinal Cord Neurons. J Mol Neurosci 2016; 58:517-24. [PMID: 26798048 DOI: 10.1007/s12031-015-0709-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 12/28/2015] [Indexed: 11/26/2022]
Abstract
The failure of neurite outgrowth in the adult mammalian spinal cord injury is thought to be attributed to the intrinsic growth ability of mature neurons. Ephrin/Eph system is a major growth regulator of many axonal guidance processes. EphA4 is expressed specifically in traumatic central nervous system (CNS) and dynamically regulate target gene expression, suggesting that it may be associated with neural regeneration. Here, we found an alteration in temporal expression of miR-93 following a contusive spinal cord injury (SCI) in adult rats. The messenger RNA (mRNA) expression level of miR-93 was upregulated and the protein expression levels of EphA4, p-Ephexin, and active RhoA were all decreased in traumatic spinal cord relative to those with an intact spinal cord. Infection of cultured spinal cord neurons (SCNs) with miR-93 mimic led to neuronal growth promotion and decreased levels of EphA4, p-Ephexin, and active RhoA protein expression. Dual-luciferase reporter assay confirmed that miR-93 bound to the three prime untranslated region (3' UTR) of EphA4 and inhibited the expression of EphA4 mRNA. These findings provide evidence that miR-93 inhibits EphA4 expression, decreased EphA4 expression could promote neurite outgrowth in SCNs due to reduced levels of p-Ephexin and active RhoA.
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Affiliation(s)
- Xiaogang Chen
- Department of Orthopedic Surgery, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu Province, China
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
| | - Huilin Yang
- Department of Orthopedic Surgery, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu Province, China.
| | - Xiaoqing Zhou
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
| | - Lin Zhang
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
| | - Xiaoqing Lu
- Department of Orthopedic Surgery, Huai'an NO.2 People's Hospital, Affiliated Huai'an Hospital of Xuzhou Medical College, Huai'an, 223002, Jiangsu Province, China
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Colak D, Ji SJ, Porse BT, Jaffrey SR. Regulation of axon guidance by compartmentalized nonsense-mediated mRNA decay. Cell 2013; 153:1252-65. [PMID: 23746841 PMCID: PMC3685487 DOI: 10.1016/j.cell.2013.04.056] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 03/05/2013] [Accepted: 04/30/2013] [Indexed: 12/13/2022]
Abstract
Growth cones enable axons to navigate toward their targets by responding to extracellular signaling molecules. Growth-cone responses are mediated in part by the local translation of axonal messenger RNAs (mRNAs). However, the mechanisms that regulate local translation are poorly understood. Here we show that Robo3.2, a receptor for the Slit family of guidance cues, is synthesized locally within axons of commissural neurons. Robo3.2 translation is induced by floor-plate-derived signals as axons cross the spinal cord midline. Robo3.2 is also a predicted target of the nonsense-mediated mRNA decay (NMD) pathway. We find that NMD regulates Robo3.2 synthesis by inducing the degradation of Robo3.2 transcripts in axons that encounter the floor plate. Commissural neurons deficient in NMD proteins exhibit aberrant axonal trajectories after crossing the midline, consistent with misregulation of Robo3.2 expression. These data show that local translation is regulated by mRNA stability and that NMD acts locally to influence axonal pathfinding.
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Affiliation(s)
- Dilek Colak
- Department of Pharmacology, Weill Medical College, Cornell University, New York, NY 10065, USA
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Yamauchi K, Varadarajan SG, Li JE, Butler SJ. Type Ib BMP receptors mediate the rate of commissural axon extension through inhibition of cofilin activity. Development 2013; 140:333-42. [PMID: 23250207 PMCID: PMC3597210 DOI: 10.1242/dev.089524] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/2012] [Indexed: 11/20/2022]
Abstract
Bone morphogenetic proteins (BMPs) have unexpectedly diverse activities establishing different aspects of dorsal neural circuitry in the developing spinal cord. Our recent studies have shown that, in addition to spatially orienting dorsal commissural (dI1) axons, BMPs supply 'temporal' information to commissural axons to specify their rate of growth. This information ensures that commissural axons reach subsequent signals at particular times during development. However, it remains unresolved how commissural neurons specifically decode this activity of BMPs to result in their extending axons at a specific speed through the dorsal spinal cord. We have addressed this question by examining whether either of the type I BMP receptors (Bmpr), BmprIa and BmprIb, have a role controlling the rate of commissural axon growth. BmprIa and BmprIb exhibit a common function specifying the identity of dorsal cell fate in the spinal cord, whereas BmprIb alone mediates the ability of BMPs to orient axons. Here, we show that BmprIb, and not BmprIa, is additionally required to control the rate of commissural axon extension. We have also determined the intracellular effector by which BmprIb regulates commissural axon growth. We show that BmprIb has a novel role modulating the activity of the actin-severing protein cofilin. These studies reveal the mechanistic differences used by distinct components of the canonical Bmpr complex to mediate the diverse activities of the BMPs.
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Affiliation(s)
- Ken Yamauchi
- Neuroscience Graduate Program, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
- Department of Biological Sciences, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
| | - Supraja G. Varadarajan
- Graduate Studies in the Biological Sciences – Neurobiology, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
- Department of Biological Sciences, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
| | - Joseph E. Li
- Department of Biological Sciences, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
| | - Samantha J. Butler
- Neuroscience Graduate Program, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
- Department of Biological Sciences, HNB 201, 3641 Watt Way, University of Southern California, Los Angeles, CA 90089, USA
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Moore SW, Zhang X, Lynch CD, Sheetz MP. Netrin-1 attracts axons through FAK-dependent mechanotransduction. J Neurosci 2012; 32:11574-85. [PMID: 22915102 PMCID: PMC3461192 DOI: 10.1523/jneurosci.0999-12.2012] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 06/01/2012] [Accepted: 06/29/2012] [Indexed: 11/21/2022] Open
Abstract
The mechanism by which extracellular cues influence intracellular biochemical cascades that guide axons is important, yet poorly understood. Because of the mechanical nature of axon extension, we explored whether the physical interactions of growth cones with their guidance cues might be involved. In the context of mouse spinal commissural neuron axon attraction to netrin-1, we found that mechanical attachment of netrin-1 to the substrate was required for axon outgrowth, growth cone expansion, axon attraction and phosphorylation of focal adhesion kinase (FAK) and Crk-associated substrate (CAS). Myosin II activity was necessary for traction forces >30 pN on netrin-1. Interestingly, while these myosin II-dependent forces on netrin-1 substrates or beads were needed to increase the kinase activity and phosphorylation of FAK, they were not necessary for netrin-1 to increase CAS phosphorylation. When FAK kinase activity was inhibited, the growth cone's ability to recruit additional adhesions and to generate forces >60 pN on netrin-1 was disrupted. Together, these findings demonstrate an important role for mechanotransduction during chemoattraction to netrin-1 and that mechanical activation of FAK reinforces interactions with netrin-1 allowing greater forces to be exerted.
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Affiliation(s)
- Simon W Moore
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
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