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Gupta S, Heinrichs E, Novitch BG, Butler SJ. Investigating the basis of lineage decisions and developmental trajectories in the dorsal spinal cord through pseudotime analyses. Development 2024; 151:dev202209. [PMID: 38804879 PMCID: PMC11166460 DOI: 10.1242/dev.202209] [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: 07/24/2023] [Accepted: 04/18/2024] [Indexed: 05/29/2024]
Abstract
Dorsal interneurons (dIs) in the spinal cord encode the perception of touch, pain, heat, itchiness and proprioception. Previous studies using genetic strategies in animal models have revealed important insights into dI development, but the molecular details of how dIs arise as distinct populations of neurons remain incomplete. We have developed a resource to investigate dI fate specification by combining a single-cell RNA-Seq atlas of mouse embryonic stem cell-derived dIs with pseudotime analyses. To validate this in silico resource as a useful tool, we used it to first identify genes that are candidates for directing the transition states that lead to distinct dI lineage trajectories, and then validated them using in situ hybridization analyses in the developing mouse spinal cord in vivo. We have also identified an endpoint of the dI5 lineage trajectory and found that dIs become more transcriptionally homogeneous during terminal differentiation. This study introduces a valuable tool for further discovery about the timing of gene expression during dI differentiation and demonstrates its utility in clarifying dI lineage relationships.
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Affiliation(s)
- Sandeep Gupta
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Eric Heinrichs
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Genetics and Genomics Graduate Program, University of California Los Angeles, Los Angeles, CA 90095, USA
| | - Bennett G. Novitch
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Intellectual and Developmental Disabilities Research Center, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Samantha J. Butler
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Intellectual and Developmental Disabilities Research Center, University of California, Los Angeles, Los Angeles, CA 90095, USA
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Gupta S, Heinrichs E, Novitch BG, Butler SJ. Investigating the basis of lineage decisions and developmental trajectories in the dorsal spinal cord through pseudotime analyses. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.07.24.550380. [PMID: 37546781 PMCID: PMC10402035 DOI: 10.1101/2023.07.24.550380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Dorsal interneurons (dIs) in the spinal cord encode the perception of touch, pain, heat, itch, and proprioception. While previous studies using genetic strategies in animal models have revealed important insights into dI development, the molecular details by which dIs arise as distinct populations of neurons remain incomplete. We have developed a resource to investigate dI fate specification by combining a single-cell RNA-Seq atlas of mouse ESC-derived dIs with pseudotime analyses. To validate this in silico resource as a useful tool, we used it to first identify novel genes that are candidates for directing the transition states that lead to distinct dI lineage trajectories, and then validated them using in situ hybridization analyses in the developing mouse spinal cord in vivo . We have also identified a novel endpoint of the dI5 lineage trajectory and found that dIs become more transcriptionally homogenous during terminal differentiation. Together, this study introduces a valuable tool for further discovery about the timing of gene expression during dI differentiation and demonstrates its utility clarifying dI lineage relationships. Summary statement Pseudotime analyses of embryonic stem cell-derived dorsal spinal interneurons reveals both novel regulators and lineage relationships between different interneuron populations.
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Weible MW, Lovelace MD, Mundell HD, Pang TWR, Chan-Ling T. BMPRII + neural precursor cells isolated and characterized from organotypic neurospheres: an in vitro model of human fetal spinal cord development. Neural Regen Res 2024; 19:447-457. [PMID: 37488910 PMCID: PMC10503628 DOI: 10.4103/1673-5374.373669] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 11/12/2022] [Accepted: 03/06/2023] [Indexed: 07/26/2023] Open
Abstract
Roof plate secretion of bone morphogenetic proteins (BMPs) directs the cellular fate of sensory neurons during spinal cord development, including the formation of the ascending sensory columns, though their biology is not well understood. Type-II BMP receptor (BMPRII), the cognate receptor, is expressed by neural precursor cells during embryogenesis; however, an in vitro method of enriching BMPRII+ human neural precursor cells (hNPCs) from the fetal spinal cord is absent. Immunofluorescence was undertaken on intact second-trimester human fetal spinal cord using antibodies to BMPRII and leukemia inhibitory factor (LIF). Regions of highest BMPRII+ immunofluorescence localized to sensory columns. Parenchymal and meningeal-associated BMPRII+ vascular cells were identified in both intact fetal spinal cord and cortex by co-positivity with vascular lineage markers, CD34/CD39. LIF immunostaining identified a population of somas concentrated in dorsal and ventral horn interneurons, mirroring the expression of LIF receptor/CD118. A combination of LIF supplementation and high-density culture maintained culture growth beyond 10 passages, while synergistically increasing the proportion of neurospheres with a stratified, cytoarchitecture. These neurospheres were characterized by BMPRII+/MAP2ab+/-/βIII-tubulin+/nestin-/vimentin-/GFAP-/NeuN- surface hNPCs surrounding a heterogeneous core of βIII-tubulin+/nestin+/vimentin+/GFAP+/MAP2ab-/NeuN- multipotent precursors. Dissociated cultures from tripotential neurospheres contained neuronal (βIII-tubulin+), astrocytic (GFAP+), and oligodendrocytic (O4+) lineage cells. Fluorescence-activated cell sorting-sorted BMPRII+ hNPCs were MAP2ab+/-/βIII-tubulin+/GFAP-/O4- in culture. This is the first isolation of BMPRII+ hNPCs identified and characterized in human fetal spinal cords. Our data show that LIF combines synergistically with high-density reaggregate cultures to support the organotypic reorganization of neurospheres, characterized by surface BMPRII+ hNPCs. Our study has provided a new methodology for an in vitro model capable of amplifying human fetal spinal cord cell numbers for > 10 passages. Investigations of the role BMPRII plays in spinal cord development have primarily relied upon mouse and rat models, with interpolations to human development being derived through inference. Because of significant species differences between murine biology and human, including anatomical dissimilarities in central nervous system (CNS) structure, the findings made in murine models cannot be presumed to apply to human spinal cord development. For these reasons, our human in vitro model offers a novel tool to better understand neurodevelopmental pathways, including BMP signaling, as well as spinal cord injury research and testing drug therapies.
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Affiliation(s)
- Michael W. Weible
- Bosch Institute, Discipline of Anatomy and Histology (F13), University of Sydney, Sydney, NSW, Australia
- School of Environment and Science, Griffith University, Nathan, QLD, Australia
| | - Michael D. Lovelace
- Bosch Institute, Discipline of Anatomy and Histology (F13), University of Sydney, Sydney, NSW, Australia
- Discipline of Medicine, Nepean Clinical School, Faculty of Medicine and Health, University of Sydney, Kingswood, NSW, Australia
| | - Hamish D. Mundell
- Bosch Institute, Discipline of Anatomy and Histology (F13), University of Sydney, Sydney, NSW, Australia
- New South Wales Brain Tissue Resource Centre, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Charles Perkins Centre (D17), Sydney, NSW, Australia
| | - Tsz Wai Rosita Pang
- Bosch Institute, Discipline of Anatomy and Histology (F13), University of Sydney, Sydney, NSW, Australia
| | - Tailoi Chan-Ling
- Bosch Institute, Discipline of Anatomy and Histology (F13), University of Sydney, Sydney, NSW, Australia
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Frith TJR, Briscoe J, Boezio GLM. From signalling to form: the coordination of neural tube patterning. Curr Top Dev Biol 2023; 159:168-231. [PMID: 38729676 DOI: 10.1016/bs.ctdb.2023.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2024]
Abstract
The development of the vertebrate spinal cord involves the formation of the neural tube and the generation of multiple distinct cell types. The process starts during gastrulation, combining axial elongation with specification of neural cells and the formation of the neuroepithelium. Tissue movements produce the neural tube which is then exposed to signals that provide patterning information to neural progenitors. The intracellular response to these signals, via a gene regulatory network, governs the spatial and temporal differentiation of progenitors into specific cell types, facilitating the assembly of functional neuronal circuits. The interplay between the gene regulatory network, cell movement, and tissue mechanics generates the conserved neural tube pattern observed across species. In this review we offer an overview of the molecular and cellular processes governing the formation and patterning of the neural tube, highlighting how the remarkable complexity and precision of vertebrate nervous system arises. We argue that a multidisciplinary and multiscale understanding of the neural tube development, paired with the study of species-specific strategies, will be crucial to tackle the open questions.
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Affiliation(s)
| | - James Briscoe
- The Francis Crick Institute, London, United Kingdom.
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Alvarez S, Gupta S, Honeychurch K, Mercado-Ayon Y, Kawaguchi R, Butler SJ. Netrin1 patterns the dorsal spinal cord through modulation of Bmp signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.02.565384. [PMID: 37961605 PMCID: PMC10635094 DOI: 10.1101/2023.11.02.565384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
We have identified an unexpected role for netrin1 as a suppressor of bone morphogenetic protein (Bmp) signaling in the developing dorsal spinal cord. Using a combination of gain- and loss-of-function approaches in chicken, embryonic stem cell (ESC), and mouse models, we have observed that manipulating the level of netrin1 specifically alters the patterning of the Bmp-dependent dorsal interneurons (dIs), dI1-dI3. Altered netrin1 levels also change Bmp signaling activity, as measured by bioinformatics, and monitoring phosophoSmad1/5/8 activation, the canonical intermediate of Bmp signaling, and Id levels, a known Bmp target. Together, these studies support the hypothesis that netrin1 acts from the intermediate spinal cord to regionally confine Bmp signaling to the dorsal spinal cord. Thus, netrin1 has reiterative activities shaping dorsal spinal circuits, first by regulating cell fate decisions and then acting as a guidance cue to direct axon extension.
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Gupta S, Kawaguchi R, Heinrichs E, Gallardo S, Castellanos S, Mandric I, Novitch BG, Butler SJ. In vitro atlas of dorsal spinal interneurons reveals Wnt signaling as a critical regulator of progenitor expansion. Cell Rep 2022; 40:111119. [PMID: 35858555 PMCID: PMC9414195 DOI: 10.1016/j.celrep.2022.111119] [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] [Received: 11/08/2021] [Revised: 04/12/2022] [Accepted: 06/28/2022] [Indexed: 11/03/2022] Open
Abstract
Restoring sensation after injury or disease requires a reproducible method for generating large quantities of bona fide somatosensory interneurons. Toward this goal, we assess the mechanisms by which dorsal spinal interneurons (dIs; dI1-dI6) can be derived from mouse embryonic stem cells (mESCs). Using two developmentally relevant growth factors, retinoic acid (RA) and bone morphogenetic protein (BMP) 4, we recapitulate the complete in vivo program of dI differentiation through a neuromesodermal intermediate. Transcriptional profiling reveals that mESC-derived dIs strikingly resemble endogenous dIs, with the correct molecular and functional signatures. We further demonstrate that RA specifies dI4-dI6 fates through a default multipotential state, while the addition of BMP4 induces dI1-dI3 fates and activates Wnt signaling to enhance progenitor proliferation. Constitutively activating Wnt signaling permits the dramatic expansion of neural progenitor cultures. These cultures retain the capacity to differentiate into diverse populations of dIs, thereby providing a method of increasing neuronal yield.
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Affiliation(s)
- Sandeep Gupta
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA.
| | - Riki Kawaguchi
- Department of Psychiatry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Eric Heinrichs
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Genetics and Genomics Graduate Program, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Salena Gallardo
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Interdepartmental Graduate Program, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Stephanie Castellanos
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA; CIRM Bridges to Research Program, California State University, Northridge, Los Angeles, CA, USA
| | - Igor Mandric
- Department of Computer Science, Samueli School of Engineering, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Bennett G Novitch
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA; Intellectual & Developmental Disabilities Research Center, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Samantha J Butler
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA; Intellectual & Developmental Disabilities Research Center, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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Le Dréau G. BuMPing Into Neurogenesis: How the Canonical BMP Pathway Regulates Neural Stem Cell Divisions Throughout Space and Time. Front Neurosci 2022; 15:819990. [PMID: 35153664 PMCID: PMC8829030 DOI: 10.3389/fnins.2021.819990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 12/28/2021] [Indexed: 11/13/2022] Open
Abstract
Bone morphogenetic proteins (BMPs) are secreted factors that contribute to many aspects of the formation of the vertebrate central nervous system (CNS), from the initial shaping of the neural primordium to the maturation of the brain and spinal cord. In particular, the canonical (SMAD1/5/8-dependent) BMP pathway appears to play a key role during neurogenesis, its activity dictating neural stem cell fate decisions and thereby regulating the growth and homeostasis of the CNS. In this mini-review, I summarize accumulating evidence demonstrating how the canonical BMP activity promotes the amplification and/or maintenance of neural stem cells at different times and in diverse regions of the vertebrate CNS, and highlight findings suggesting that this function is evolutionarily conserved.
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Gupta S, Butler SJ. Getting in touch with your senses: Mechanisms specifying sensory interneurons in the dorsal spinal cord. WIREs Mech Dis 2021; 13:e1520. [PMID: 34730293 PMCID: PMC8459260 DOI: 10.1002/wsbm.1520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/10/2021] [Accepted: 01/11/2021] [Indexed: 11/18/2022]
Abstract
The spinal cord is functionally and anatomically divided into ventrally derived motor circuits and dorsally derived somatosensory circuits. Sensory stimuli originating either at the periphery of the body, or internally, are relayed to the dorsal spinal cord where they are processed by distinct classes of sensory dorsal interneurons (dIs). dIs convey sensory information, such as pain, heat or itch, either to the brain, and/or to the motor circuits to initiate the appropriate response. They also regulate the intensity of sensory information and are the major target for the opioid analgesics. While the developmental mechanisms directing ventral and dorsal cell fates have been hypothesized to be similar, more recent research has suggested that dI fates are specified by novel mechanisms. In this review, we will discuss the molecular events that specify dorsal neuronal patterning in the spinal cord, thereby generating diverse dI identities. We will then discuss how this molecular understanding has led to the development of robust stem cell methods to derive multiple spinal cell types, including the dIs, and the implication of these studies for treating spinal cord injuries and neurodegenerative diseases. This article is categorized under: Neurological Diseases > Stem Cells and Development.
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Affiliation(s)
- Sandeep Gupta
- Department of NeurobiologyUniversity of California, Los AngelesLos AngelesCaliforniaUSA
| | - Samantha J. Butler
- Department of NeurobiologyUniversity of California, Los AngelesLos AngelesCaliforniaUSA
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell ResearchUniversity of California, Los AngelesLos AngelesCaliforniaUSA
- Intellectual and Developmental Disabilities Research CenterUniversity of California, Los AngelesLos AngelesCaliforniaUSA
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Suciu SK, Long AB, Caspary T. Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting. Genetics 2021; 218:6300527. [PMID: 34132778 PMCID: PMC8864748 DOI: 10.1093/genetics/iyab084] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/15/2021] [Indexed: 01/07/2023] Open
Abstract
Patients with the ciliopathy Joubert syndrome present with physical anomalies, intellectual disability, and a hindbrain malformation described as the "molar tooth sign" due to its appearance on an MRI. This radiological abnormality results from a combination of hypoplasia of the cerebellar vermis and inappropriate targeting of the white matter tracts of the superior cerebellar peduncles. ARL13B is a cilia-enriched regulatory GTPase established to regulate cell fate, cell proliferation, and axon guidance through vertebrate Hedgehog signaling. In patients, mutations in ARL13B cause Joubert syndrome. To understand the etiology of the molar tooth sign, we used mouse models to investigate the role of ARL13B during cerebellar development. We found that ARL13B regulates superior cerebellar peduncle targeting and these fiber tracts require Hedgehog signaling for proper guidance. However, in mouse, the Joubert-causing R79Q mutation in ARL13B does not disrupt Hedgehog signaling nor does it impact tract targeting. We found a small cerebellar vermis in mice lacking ARL13B function but no cerebellar vermis hypoplasia in mice expressing the Joubert-causing R79Q mutation. In addition, mice expressing a cilia-excluded variant of ARL13B that transduces Hedgehog normally showed normal tract targeting and vermis width. Taken together, our data indicate that ARL13B is critical for the control of cerebellar vermis width as well as superior cerebellar peduncle axon guidance, likely via Hedgehog signaling. Thus, our work highlights the complexity of ARL13B in molar tooth sign etiology.
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Affiliation(s)
- Sarah K Suciu
- Genetics and Molecular Biology Graduate Program, Emory University, Atlanta, GA 30322, USA,Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Alyssa B Long
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Tamara Caspary
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA,Corresponding author: Department of Human Genetics, 615 Michael Street, Suite 301, Atlanta, GA 30322.
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Alvarez S, Varadarajan SG, Butler SJ. Dorsal commissural axon guidance in the developing spinal cord. Curr Top Dev Biol 2020; 142:197-231. [PMID: 33706918 DOI: 10.1016/bs.ctdb.2020.10.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Commissural axons have been a key model system for identifying axon guidance signals in vertebrates. This review summarizes the current thinking about the molecular and cellular mechanisms that establish a specific commissural neural circuit: the dI1 neurons in the developing spinal cord. We assess the contribution of long- and short-range signaling while sequentially following the developmental timeline from the birth of dI1 neurons, to the extension of commissural axons first circumferentially and then contralaterally into the ventral funiculus.
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Affiliation(s)
- Sandy Alvarez
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Molecular Biology Interdepartmental Doctoral Program, University of California, Los Angeles, CA, United States
| | | | - Samantha J Butler
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, United States.
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Andrews MG, Kong J, Novitch BG, Butler SJ. New perspectives on the mechanisms establishing the dorsal-ventral axis of the spinal cord. Curr Top Dev Biol 2018; 132:417-450. [PMID: 30797516 DOI: 10.1016/bs.ctdb.2018.12.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Distinct classes of neurons arise at different positions along the dorsal-ventral axis of the spinal cord leading to spinal neurons being segregated along this axis according to their physiological properties and functions. Thus, the neurons associated with motor control are generally located in, or adjacent to, the ventral horn whereas the interneurons (INs) that mediate sensory activities are present within the dorsal horn. Here, we review classic and recent studies examining the developmental mechanisms that establish the dorsal-ventral axis in the embryonic spinal cord. Intriguingly, while the cellular organization of the dorsal and ventral halves of the spinal cord looks superficially similar during early development, the underlying molecular mechanisms that establish dorsal vs ventral patterning are markedly distinct. For example, the ventral spinal cord is patterned by the actions of a single growth factor, sonic hedgehog (Shh) acting as a morphogen, i.e., concentration-dependent signal. Recent studies have shed light on the mechanisms by which the spatial and temporal gradient of Shh is transduced by cells to elicit the generation of different classes of ventral INs, and motor neurons (MNs). In contrast, the dorsal spinal cord is patterned by the action of multiple factors, most notably by members of the bone morphogenetic protein (BMP) and Wnt families. While less is known about dorsal patterning, recent studies have suggested that the BMPs do not act as morphogens to specify dorsal IN identities as previously proposed, rather each BMP has signal-specific activities. Finally, we consider the promise that elucidation of these mechanisms holds for neural repair.
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Affiliation(s)
- Madeline G Andrews
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Neuroscience Graduate Program, University of California, Los Angeles, CA, United States
| | - Jennifer Kong
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Neuroscience Graduate Program, University of California, Los Angeles, CA, United States
| | - Bennett G Novitch
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, United States
| | - Samantha J Butler
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, United States.
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Yang Z, Jia H, Bai Y, Wang W. Bone morphogenetic protein 4 expression in the developing lumbosacral spinal cord of rat embryos with anorectal malformations. Int J Dev Neurosci 2018; 69:32-38. [PMID: 29959980 DOI: 10.1016/j.ijdevneu.2018.06.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2018] [Revised: 06/22/2018] [Accepted: 06/22/2018] [Indexed: 01/12/2023] Open
Abstract
Although there are improvements in treatment of anorectal malformations (ARMs), patients can still develop fecal incontinence, constipation, and soiling with loss in quality of life. Recent evidence suggests that malformations in the lumbosacral spinal cord are one of the factors that affect postoperative anorectal function. However, the underlying mechanism that produces these malformations has yet to be elucidated. The bone morphogenetic proteins (BMPs) comprise a large group of highly conserved molecules that are involved in multiple processes and play important roles in the formation, development, and differentiation of the spinal cord. This study was designed to investigate the levels of BMP4 expression in the lumbosacral spinal cord in ARMs rat embryos induced by ethylenethiourea (ETU). Specifically, we assessed the association of BMP4 levels with the maldevelopment of the lumbosacral spinal cord and whether BMP4 acted through the canonical intracellular pathway in embryonic rats with ARMs. BMP4 expression was confirmed with immunohistochemical staining, RT-qPCR and western blot analyses of embryonic day (E) 16, E17, E19 and E21 embryos, moreover Smad1/5 and pSmad1/5 expression were confirmed with western blot analyses at peak time point of BMP4 expression. Our results reveal that BMP4 expression in the lumbosacral spinal cord of ARMs rat embryos is decreased at both the mRNA and protein levels and could decrease the phosphorylation of smad1/5, when compared with their expression levels in normal tissue. These results also suggest that reductions in BMP4 expression were possibly responsible for dysfunction of the lumbosacral spinal cord during late developmental stages in ARMs fetal rats. Taken together, we conclude a role for BMP4 in the pathogenesis of lumbosacral spinal cord maldevelopment in developing ARMs rats.
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Affiliation(s)
- Zhonghua Yang
- Department of Pediatric Surgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China
| | - Huimin Jia
- Department of Pediatric Surgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China
| | - Yuzuo Bai
- Department of Pediatric Surgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China
| | - Weilin Wang
- Department of Pediatric Surgery, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China.
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Deriving Dorsal Spinal Sensory Interneurons from Human Pluripotent Stem Cells. Stem Cell Reports 2018; 10:390-405. [PMID: 29337120 PMCID: PMC5832443 DOI: 10.1016/j.stemcr.2017.12.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 12/14/2017] [Accepted: 12/15/2017] [Indexed: 12/28/2022] Open
Abstract
Cellular replacement therapies for neurological conditions use human embryonic stem cell (hESC)- or induced pluripotent stem cell (hiPSC)-derived neurons to replace damaged or diseased populations of neurons. For the spinal cord, significant progress has been made generating the in-vitro-derived motor neurons required to restore coordinated movement. However, there is as yet no protocol to generate in-vitro-derived sensory interneurons (INs), which permit perception of the environment. Here, we report on the development of a directed differentiation protocol to derive sensory INs for both hESCs and hiPSCs. Two developmentally relevant factors, retinoic acid in combination with bone morphogenetic protein 4, can be used to generate three classes of sensory INs: the proprioceptive dI1s, the dI2s, and mechanosensory dI3s. Critical to this protocol is the competence state of the neural progenitors, which changes over time. This protocol will facilitate developing cellular replacement therapies to reestablish sensory connections in injured patients. Robust protocol to generate spinal sensory neurons from human pluripotent cells RA ± BMP4 direct hPSCs toward the dI1, dI2, and dI3 classes of dorsal interneurons Only neural progenitors in the correct competence state respond to RA/BMP4 signals
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14
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Andrews MG, Del Castillo LM, Ochoa-Bolton E, Yamauchi K, Smogorzewski J, Butler SJ. BMPs direct sensory interneuron identity in the developing spinal cord using signal-specific not morphogenic activities. eLife 2017; 6. [PMID: 28925352 PMCID: PMC5605194 DOI: 10.7554/elife.30647] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 08/24/2017] [Indexed: 02/06/2023] Open
Abstract
The Bone Morphogenetic Protein (BMP) family reiteratively signals to direct disparate cellular fates throughout embryogenesis. In the developing dorsal spinal cord, multiple BMPs are required to specify sensory interneurons (INs). Previous studies suggested that the BMPs act as concentration-dependent morphogens to direct IN identity, analogous to the manner in which sonic hedgehog patterns the ventral spinal cord. However, it remains unresolved how multiple BMPs would cooperate to establish a unified morphogen gradient. Our studies support an alternative model: BMPs have signal-specific activities directing particular IN fates. Using chicken and mouse models, we show that the identity, not concentration, of the BMP ligand directs distinct dorsal identities. Individual BMPs promote progenitor patterning or neuronal differentiation by their activation of different type I BMP receptors and distinct modulations of the cell cycle. Together, this study shows that a 'mix and match' code of BMP signaling results in distinct classes of sensory INs.
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Affiliation(s)
- Madeline G Andrews
- Department of Neurobiology, University of California, Los Angeles, United States.,Neuroscience Graduate Program, University of California, Los Angeles, United States.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, United States
| | - Lorenzo M Del Castillo
- Department of Neurobiology, University of California, Los Angeles, United States.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, United States.,CIRM Bridges to Research Program, California State University, Northridge, United States
| | - Eliana Ochoa-Bolton
- Department of Neurobiology, University of California, Los Angeles, United States.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, United States.,CIRM Bridges to Research Program, California State University, Northridge, United States
| | - Ken Yamauchi
- Department of Neurobiology, University of California, Los Angeles, United States.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, United States
| | - Jan Smogorzewski
- Department of Dermatology, University of Southern California, California, United States
| | - Samantha J Butler
- Department of Neurobiology, University of California, Los Angeles, United States.,Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, United States
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15
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Lai HC, Seal RP, Johnson JE. Making sense out of spinal cord somatosensory development. Development 2017; 143:3434-3448. [PMID: 27702783 DOI: 10.1242/dev.139592] [Citation(s) in RCA: 122] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The spinal cord integrates and relays somatosensory input, leading to complex motor responses. Research over the past couple of decades has identified transcription factor networks that function during development to define and instruct the generation of diverse neuronal populations within the spinal cord. A number of studies have now started to connect these developmentally defined populations with their roles in somatosensory circuits. Here, we review our current understanding of how neuronal diversity in the dorsal spinal cord is generated and we discuss the logic underlying how these neurons form the basis of somatosensory circuits.
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Affiliation(s)
- Helen C Lai
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Rebecca P Seal
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
| | - Jane E Johnson
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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16
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IRS4, a novel modulator of BMP/Smad and Akt signalling during early muscle differentiation. Sci Rep 2017; 7:8778. [PMID: 28821740 PMCID: PMC5562708 DOI: 10.1038/s41598-017-08676-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 07/12/2017] [Indexed: 12/27/2022] Open
Abstract
Elaborate regulatory networks of the Bone Morphogenetic Protein (BMP) pathways ensure precise signalling outcome during cell differentiation and tissue homeostasis. Here, we identified IRS4 as a novel regulator of BMP signal transduction and provide molecular insights how it integrates into the signalling pathway. We found that IRS4 interacts with the BMP receptor BMPRII and specifically targets Smad1 for proteasomal degradation consequently leading to repressed BMP/Smad signalling in C2C12 myoblasts while concomitantly activating the PI3K/Akt axis. IRS4 is present in human and primary mouse myoblasts, the expression increases during myogenic differentiation but is downregulated upon final commitment coinciding with Myogenin expression. Functionally, IRS4 promotes myogenesis in C2C12 cells, while IRS4 knockdown inhibits differentiation of myoblasts. We propose that IRS4 is particularly critical in the myoblast stage to serve as a molecular switch between BMP/Smad and Akt signalling and to thereby control cell commitment. These findings provide profound understanding of the role of BMP signalling in early myogenic differentiation and open new ways for targeting the BMP pathway in muscle regeneration.
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17
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Yoshikawa M, Masuda T, Kobayashi A, Senzaki K, Ozaki S, Aizawa S, Shiga T. Runx1 contributes to the functional switching of bone morphogenetic protein 4 (BMP4) from neurite outgrowth promoting to suppressing in dorsal root ganglion. Mol Cell Neurosci 2016; 72:114-22. [DOI: 10.1016/j.mcn.2016.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 02/10/2016] [Accepted: 02/11/2016] [Indexed: 10/22/2022] Open
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18
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Butler SJ, Bronner ME. From classical to current: analyzing peripheral nervous system and spinal cord lineage and fate. Dev Biol 2015; 398:135-46. [PMID: 25446276 PMCID: PMC4845735 DOI: 10.1016/j.ydbio.2014.09.033] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 09/22/2014] [Accepted: 09/25/2014] [Indexed: 01/13/2023]
Abstract
During vertebrate development, the central (CNS) and peripheral nervous systems (PNS) arise from the neural plate. Cells at the margin of the neural plate give rise to neural crest cells, which migrate extensively throughout the embryo, contributing to the majority of neurons and all of the glia of the PNS. The rest of the neural plate invaginates to form the neural tube, which expands to form the brain and spinal cord. The emergence of molecular cloning techniques and identification of fluorophores like Green Fluorescent Protein (GFP), together with transgenic and electroporation technologies, have made it possible to easily visualize the cellular and molecular events in play during nervous system formation. These lineage-tracing techniques have precisely demonstrated the migratory pathways followed by neural crest cells and increased knowledge about their differentiation into PNS derivatives. Similarly, in the spinal cord, lineage-tracing techniques have led to a greater understanding of the regional organization of multiple classes of neural progenitor and post-mitotic neurons along the different axes of the spinal cord and how these distinct classes of neurons assemble into the specific neural circuits required to realize their various functions. Here, we review how both classical and modern lineage and marker analyses have expanded our knowledge of early peripheral nervous system and spinal cord development.
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Affiliation(s)
- Samantha J Butler
- Department of Neurobiology, TLSB 3129, 610 Charles E Young Drive East, University of California, Los Angeles, Los Angeles, CA 90095-7239, USA; Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Marianne E Bronner
- Department of Neurobiology, TLSB 3129, 610 Charles E Young Drive East, University of California, Los Angeles, Los Angeles, CA 90095-7239, USA; Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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19
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Hegarty SV, Collins LM, Gavin AM, Roche SL, Wyatt SL, Sullivan AM, O'Keeffe GW. Canonical BMP-Smad signalling promotes neurite growth in rat midbrain dopaminergic neurons. Neuromolecular Med 2014; 16:473-89. [PMID: 24682653 DOI: 10.1007/s12017-014-8299-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 03/07/2014] [Indexed: 01/01/2023]
Abstract
Ventral midbrain (VM) dopaminergic (DA) neurons project to the dorsal striatum via the nigrostriatal pathway to regulate voluntary movements, and their loss leads to the motor dysfunction seen in Parkinson's disease (PD). Despite recent progress in the understanding of VM DA neurogenesis, the factors regulating nigrostriatal pathway development remain largely unknown. The bone morphogenetic protein (BMP) family regulates neurite growth in the developing nervous system and may contribute to nigrostriatal pathway development. Two related members of this family, BMP2 and growth differentiation factor (GDF)5, have neurotrophic effects, including promotion of neurite growth, on cultured VM DA neurons. However, the molecular mechanisms regulating their effects on DA neurons are unknown. By characterising the temporal expression profiles of endogenous BMP receptors (BMPRs) in the developing and adult rat VM and striatum, this study identified BMP2 and GDF5 as potential regulators of nigrostriatal pathway development. Furthermore, through the use of noggin, dorsomorphin and BMPR/Smad plasmids, this study demonstrated that GDF5- and BMP2-induced neurite outgrowth from cultured VM DA neurons is dependent on BMP type I receptor activation of the Smad 1/5/8 signalling pathway.
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Affiliation(s)
- Shane V Hegarty
- Department of Anatomy and Neuroscience, Biosciences Institute, University College Cork, Cork, Ireland
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20
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Wei CY, Wang HP, Zhu ZY, Sun YH. Transcriptional factors smad1 and smad9 act redundantly to mediate zebrafish ventral specification downstream of smad5. J Biol Chem 2014; 289:6604-6618. [PMID: 24488494 DOI: 10.1074/jbc.m114.549758] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Bone morphogenetic proteins (BMPs) are multifunctional growth factors that play crucial roles during embryonic development and cell fate determination. Nuclear transduction of BMP signals requires the receptor type Smad proteins, Smad1, Smad5, and Smad9. However, how these Smad proteins cooperate in vivo to regulate various developmental processes is largely unknown. In zebrafish, it was widely believed that the maternally expressed smad5 is essential for dorso-ventral (DV) patterning, and the zygotically transcribed smad1 is not required for normal DV axis establishment. In the present study, we have identified zygotically expressed smad9, which cooperates with smad1 downstream of smad5, to mediate zebrafish early DV patterning in a functional redundant manner. Although knockdown of smad1 or smad9 alone does not lead to visible dorsalization, double knockdown strongly dorsalizes zebrafish embryos, which cannot be efficiently rescued by smad5 overexpression, whereas the dorsalization induced by smad5 knockdown can be fully rescued by overexpression of smad1 or smad9. We have further revealed that the transcription initiations of smad1 and smad9 are repressed by each other, that they are direct transcriptional targets of Smad5, and that smad9, like smad1, is required for myelopoiesis. In conclusion, our study uncovers that smad1 and smad9 act redundantly to each other downstream of smad5 to mediate ventral specification and to regulate embryonic myelopoiesis.
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Affiliation(s)
- Chang-Yong Wei
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 7 Donghu South Road, Wuhan 430072, China; University of the Chinese Academy of Sciences, Beijing 100049, China
| | - Hou-Peng Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 7 Donghu South Road, Wuhan 430072, China
| | - Zuo-Yan Zhu
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 7 Donghu South Road, Wuhan 430072, China
| | - Yong-Hua Sun
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, 7 Donghu South Road, Wuhan 430072, China.
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21
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Misra K, Luo H, Li S, Matise M, Xiang M. Asymmetric activation of Dll4-Notch signaling by Foxn4 and proneural factors activates BMP/TGFβ signaling to specify V2b interneurons in the spinal cord. Development 2013; 141:187-98. [PMID: 24257627 DOI: 10.1242/dev.092536] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
During development of the ventral spinal cord, the V2 interneurons emerge from p2 progenitors and diversify into two major subtypes, V2a and V2b, that play key roles in locomotor coordination. Dll4-mediated Notch activation in a subset of p2 precursors constitutes the crucial first step towards generating neuronal diversity in this domain. The mechanism behind the asymmetric Notch activation and downstream signaling events are, however, unknown at present. We show here that the Ascl1 and Neurog basic helix-loop-helix (bHLH) proneural factors are expressed in a mosaic pattern in p2 progenitors and that Foxn4 is required for setting and maintaining this expression mosaic. By binding directly to a conserved Dll4 enhancer, Foxn4 and Ascl1 activate Dll4 expression, whereas Neurog proteins prevent this effect, thereby resulting in asymmetric activation of Dll4 expression in V2 precursors expressing different combinations of proneural and Foxn4 transcription factors. Lineage tracing using the Cre-LoxP system reveals selective expression of Dll4 in V2a precursors, whereas Dll4 expression is initially excluded from V2b precursors. We provide evidence that BMP/TGFβ signaling is activated in V2b precursors and that Dll4-mediated Notch signaling is responsible for this activation. Using a gain-of-function approach and by inhibiting BMP/TGFβ signal transduction with pathway antagonists and RNAi knockdown, we further demonstrate that BMP/TGFβ signaling is both necessary and sufficient for V2b fate specification. Our data together thus suggest that the mosaic expression of Foxn4 and proneural factors may serve as the trigger to initiate asymmetric Dll4-Notch and subsequent BMP/TGFβ signaling events required for neuronal diversity in the V2 domain.
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Affiliation(s)
- Kamana Misra
- Center for Advanced Biotechnology and Medicine and Department of Pediatrics, Rutgers University-Robert Wood Johnson Medical School, 679 Hoes Lane West, Piscataway, NJ 08854, USA
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22
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Le Dréau G, Martí E. The multiple activities of BMPs during spinal cord development. Cell Mol Life Sci 2013; 70:4293-305. [PMID: 23673983 PMCID: PMC11113619 DOI: 10.1007/s00018-013-1354-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 04/25/2013] [Accepted: 04/29/2013] [Indexed: 12/19/2022]
Abstract
Bone morphogenetic proteins (BMPs) are one of the main classes of multi-faceted secreted factors that drive vertebrate development. A growing body of evidence indicates that BMPs contribute to the formation of the central nervous system throughout its development, from the initial shaping of the neural primordium to the generation and maturation of the different cell types that form the functional adult nervous tissue. In this review, we focus on the multiple activities of BMPs during spinal cord development, paying particular attention to recent results that highlight the complexity of BMP signaling during this process. These findings emphasize the unique capacity of these signals to mediate various functions in the same tissue throughout development, recruiting diverse effectors and strategies to instruct their target cells.
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Affiliation(s)
- Gwenvael Le Dréau
- Instituto de Biología Molecular de Barcelona, CSIC, Parc Científic de Barcelona, C/Baldiri i Reixac 10-15, 08028 Barcelona, Spain
| | - Elisa Martí
- Instituto de Biología Molecular de Barcelona, CSIC, Parc Científic de Barcelona, C/Baldiri i Reixac 10-15, 08028 Barcelona, Spain
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23
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Gaber ZB, Butler SJ, Novitch BG. PLZF regulates fibroblast growth factor responsiveness and maintenance of neural progenitors. PLoS Biol 2013; 11:e1001676. [PMID: 24115909 PMCID: PMC3792860 DOI: 10.1371/journal.pbio.1001676] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2013] [Accepted: 08/29/2013] [Indexed: 12/31/2022] Open
Abstract
A transcription factor called Promyelocytic Leukemia Zinc Finger (PLZF) calibrates the balance between spinal cord progenitor maintenance and differentiation by enhancing their sensitivity to mitogens that are present in developing embryos. Distinct classes of neurons and glial cells in the developing spinal cord arise at specific times and in specific quantities from spatially discrete neural progenitor domains. Thus, adjacent domains can exhibit marked differences in their proliferative potential and timing of differentiation. However, remarkably little is known about the mechanisms that account for this regional control. Here, we show that the transcription factor Promyelocytic Leukemia Zinc Finger (PLZF) plays a critical role shaping patterns of neuronal differentiation by gating the expression of Fibroblast Growth Factor (FGF) Receptor 3 and responsiveness of progenitors to FGFs. PLZF elevation increases FGFR3 expression and STAT3 pathway activity, suppresses neurogenesis, and biases progenitors towards glial cell production. In contrast, PLZF loss reduces FGFR3 levels, leading to premature neuronal differentiation. Together, these findings reveal a novel transcriptional strategy for spatially tuning the responsiveness of distinct neural progenitor groups to broadly distributed mitogenic signals in the embryonic environment. The embryonic spinal cord is organized into an array of discrete neural progenitor domains along the dorsoventral axis. Most of these domains undergo two periods of differentiation, first producing specific classes of neurons and then generating distinct populations of glial cells at later times. In addition, each of these progenitors pools exhibit marked differences in their proliferative capacities and propensity to differentiate to produce the appropriate numbers and diversity of neurons and glia needed to form functional neural circuits. The mechanisms behind this regional control of neural progenitor behavior, however, remain unclear. In this study, we identify the transcription factor Promyelocytic Leukemia Zinc Finger (PLZF) as a critical regulator of this process in the chick spinal cord. We show that PLZF is initially expressed by all spinal cord progenitors and then becomes restricted to a central domain, where it helps to limit the rate of neuronal differentiation and to preserve the progenitor pool for subsequent glial production. We also demonstrate that PLZF acts by promoting the expression of Fibroblast Growth Factor (FGF) Receptor 3, thereby enhancing the proliferative response of neural progenitors to FGFs present in developing embryos. Together, these findings reveal a novel developmental strategy for spatially controlling neural progenitor behavior by tuning their responsiveness to broadly distributed growth-promoting signals in the embryonic environment.
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Affiliation(s)
- Zachary B. Gaber
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Broad Center for Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Molecular Biology Interdepartmental Graduate Program, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
| | - Samantha J. Butler
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Broad Center for Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America
| | - Bennett G. Novitch
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Broad Center for Regenerative Medicine and Stem Cell Research, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- Molecular Biology Interdepartmental Graduate Program, David Geffen School of Medicine at UCLA, Los Angeles, California, United States of America
- * E-mail:
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24
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Jing J, Ren Y, Zong Z, Liu C, Kamiya N, Mishina Y, Liu Y, Zhou X, Feng JQ. BMP receptor 1A determines the cell fate of the postnatal growth plate. Int J Biol Sci 2013; 9:895-906. [PMID: 24163588 PMCID: PMC3807016 DOI: 10.7150/ijbs.7508] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 09/16/2013] [Indexed: 02/05/2023] Open
Abstract
Bone morphogenic proteins (BMPs) are critical for both chondrogenesis and osteogenesis. Previous studies reported that embryos deficient in Bmp receptor (Bmpr)1a or Bmpr1b in cartilage display subtle skeletal defects; however, double mutant embryos develop severe skeletal defects, suggesting a functional redundancy that is essential for early chondrogenesis. In this study, we examined the postnatal role of Bmpr1a in cartilage. In the Bmpr1a conditional knockout (cKO, a cross between Bmpr1a flox and aggrecan-CreERT2 induced by a one-time-tamoxifen injection at birth and harvested at ages of 2, 4, 8 and 20 weeks), there was essentially no long bone growth with little expression of cartilage markers such as SOX9, IHH and glycoproteins. Unexpectedly, the null growth plate was replaced by bone-like tissues, supporting the notions that the progenitor cells in the growth plate, which normally form cartilage, can form other tissues such as bone and fibrous; and that BMPR1A determines the cell fate. A working hypothesis is proposed to explain the vital role of BMPR1A in postnatal chondrogenesis.
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Affiliation(s)
- Junjun Jing
- 1. State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, China. ; 2. Department of Biomedical Sciences, Texas A&M Baylor College of Dentistry, Dallas, TX, USA
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25
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Hegarty SV, O'Keeffe GW, Sullivan AM. BMP-Smad 1/5/8 signalling in the development of the nervous system. Prog Neurobiol 2013; 109:28-41. [PMID: 23891815 DOI: 10.1016/j.pneurobio.2013.07.002] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 07/16/2013] [Accepted: 07/16/2013] [Indexed: 02/07/2023]
Abstract
The transcription factors, Smad1, Smad5 and Smad8, are the pivotal intracellular effectors of the bone morphogenetic protein (BMP) family of proteins. BMPs and their receptors are expressed in the nervous system (NS) throughout its development. This review focuses on the actions of Smad 1/5/8 in the developing NS. The mechanisms by which these Smad proteins regulate the induction of the neuroectoderm, the central nervous system (CNS) primordium, and finally the neural crest, which gives rise to the peripheral nervous system (PNS), are reviewed herein. We describe how, following neural tube closure, the most dorsal aspect of the tube becomes a signalling centre for BMPs, which directs the pattern of the development of the dorsal spinal cord (SC), through the action of Smad1, Smad5 and Smad8. The direct effects of Smad 1/5/8 signalling on the development of neuronal and non-neuronal cells from various neural progenitor cell populations are then described. Finally, this review discusses the neurodevelopmental abnormalities associated with the knockdown of Smad 1/5/8.
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Affiliation(s)
- Shane V Hegarty
- Department of Anatomy & Neuroscience, University College Cork, Cork, Ireland
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26
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BMP2 and GDF5 induce neuronal differentiation through a Smad dependant pathway in a model of human midbrain dopaminergic neurons. Mol Cell Neurosci 2013; 56:263-71. [PMID: 23831389 DOI: 10.1016/j.mcn.2013.06.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 05/24/2013] [Accepted: 06/25/2013] [Indexed: 01/12/2023] Open
Abstract
Parkinson's disease is the second most common neurodegenerative disease, and is characterised by the progressive degeneration of the nigrostriatal dopaminergic (DA) system. Current treatments are symptomatic, and do not protect against the DA neuronal loss. One of the most promising treatment approaches is the application of neurotrophic factors to rescue the remaining population of nigrostriatal DA neurons. Therefore, the identification of new neurotrophic factors for midbrain DA neurons, and the subsequent elucidation of the molecular bases of their effects, are important. Two related members of the bone morphogenetic protein (BMP) family, BMP2 and growth differentiation factor 5 (GDF5), have been shown to have neurotrophic effects on midbrain DA neurons both in vitro and in vivo. However, the molecular (signalling pathway(s)) and cellular (direct neuronal or indirect via glial cells) mechanisms of their effects remain to be elucidated. Using the SH-SH5Y human neuronal cell line, as a model of human midbrain DA neurons, we have shown that GDF5 and BMP2 induce neurite outgrowth via a direct mechanism. Furthermore, we demonstrate that these effects are dependent on BMP type I receptor activation of canonical Smad 1/5/8 signalling.
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27
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Bilaterally symmetric populations of chicken dI1 (commissural) axons cross the floor plate independently of each other. PLoS One 2013; 8:e62977. [PMID: 23646165 PMCID: PMC3639936 DOI: 10.1371/journal.pone.0062977] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Accepted: 03/28/2013] [Indexed: 12/19/2022] Open
Abstract
Axons use temporal and directional guidance cues at intermediate targets to set the rate and direction of growth towards their synaptic targets. Our recent studies have shown that disrupting the temporal guidance process, by unilaterally accelerating the rate at which spinal dI1 (commissural) axons grow, resulted in turning errors both in the ventral spinal cord and after crossing the floor plate. Here we investigate a mechanistic explanation for these defects: the accelerated dI1 axons arrive in the ventral spinal cord before necessary fasciculation cues from incoming dI1 axons from the opposite side of the spinal cord. The identification of such an interaction would support a model of selective fasciculation whereby the pioneering dI1 axons serve as guides for the processes of the bilaterally symmetrical population of dI1 neurons. To test this model, we first developed the ability to “double” in ovo electroporate the embryonic chicken spinal cord to independently manipulate the rate of growth of the two bilateral populations of dI1 axons. Second, we examined the requirement for a putative bilateral interaction by unilaterally ablating the dI1 population in cultured explants of chicken embryonic spinal cord. Surprisingly, we find no evidence for a bilateral dI1 axon interaction, rather dI1 axons appear to project independently of each other.
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28
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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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