Cadherin-20 expression by motor neurons is regulated by Sonic hedgehog during spinal cord development

During spinal cord development, Sonic hedgehog (Shh), secreted from the floor plate, plays an important role in the production of motor neurons by patterning the ventral neural tube, which establishes MN progenitor identity. It remains unknown, however, if Shh signaling plays a role in generating columnar diversity of MNs that connect distinct target muscles. Here, we report that Shh, expressed in MNs, is essential for the formation of lateral motor column (LMC) neurons in vertebrate spinal cord. This novel activity of Shh is mediated by its downstream effector ARHGAP36, whose expression is directly induced by the MN-specific transcription factor complex Isl1-Lhx3. Furthermore, we found that AKT stimulates the Shh activity to induce LMC MNs through the stabilization of ARHGAP36 proteins. Taken together, our data reveal that Shh, secreted from MNs, plays a crucial role in generating MN diversity via a regulatory axis of Shh-AKT-ARHGAP36 in the developing mouse spinal cord.

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Diminished ventral oligodendrocyte precursor generation results in the subsequent over-production of dorsal oligodendrocyte precursors of aberrant morphology and function

10.1101/2020.03.09.983908 ◽

2020 ◽

Author(s):

Lev Starikov ◽

Andreas H. Kottmann

Keyword(s):

Spinal Cord ◽

Motor Neurons ◽

Ventricular Zone ◽

Normal Numbers ◽

Spinal Cord Development ◽

Oligodendrocyte Precursor ◽

And Function ◽

Sod1 Mouse ◽

Lateral Sclerosis ◽

Ventral Spinal Cord

AbstractOligodendrocyte precursor cells (OPCs) arise sequentially first from a ventral and then from a dorsal precursor domain at the end of neurogenesis during spinal cord development. Whether the sequential production of OPCs is of physiological significance has not been examined. Here we show that ablating Shh signaling from nascent ventricular zone derivatives and partially from the floor plate results in a severe diminishment of ventral derived OPCs but normal numbers of motor neurons in the postnatal spinal cord. In the absence of ventral vOPCs, dorsal dOPCs populate the entire spinal cord resulting in an increased OPC density in the ventral horns. These OPCs take on an altered morphology, do not participate in the removal of excitatory vGlut1 synapses from injured motor neurons, and exhibit morphological features similar to those found in the vicinity of motor neurons in the SOD1 mouse model of Amyotrophic Lateral Sclerosis (ALS). Our data indicates that vOPCs prevent dOPCs from invading ventral spinal cord laminae and suggests that vOPCs have a unique ability to communicate with injured motor neurons.

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Primary Cilia, Sonic Hedgehog Signaling, and Spinal Cord Development

Cilia and Nervous System Development and Function ◽

10.1007/978-94-007-5808-7_2 ◽

2012 ◽

pp. 55-82 ◽

Cited By ~ 4

Author(s):

Laura E. Mariani ◽

Tamara Caspary

Keyword(s):

Spinal Cord ◽

Sonic Hedgehog ◽

Hedgehog Signaling ◽

Primary Cilia ◽

Sonic Hedgehog Signaling ◽

Spinal Cord Development

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The effect of sonic hedgehog on motor neuron positioning in the spinal cord during chicken embryo development

10.1101/178491 ◽

2017 ◽

Author(s):

Ciqing Yang ◽

Xiaoying Li ◽

Qiuling Li ◽

Qiong Li ◽

Han Li ◽

...

Keyword(s):

Spinal Cord ◽

Motor Neuron ◽

Embryo Development ◽

Sonic Hedgehog ◽

Motor Neurons ◽

Chicken Embryo ◽

Positional Information ◽

Underlying Mechanism ◽

Correct Location ◽

Information Cell

ABSTRACTSonic hedgehog (Shh) is a vertebrate homologue of the secreted Drosophila protein hedgehog, and is expressed by the notochord and the floor plate in the developing spinal cord. Shh provides signals relevant for positional information, cell proliferation, and possibly cell survival depending on the time and location of the expression. Although the role of Shh in providing positional information in the neural tube has been experimentally proven, the exact underlying mechanism still remains unclear. In this study, we report that overexpression of Shh affects motor neuron positioning in the spinal cord during chicken embryo development by inducing abnormalities in the structure of the motor column and motor neuron integration. In addition, Shh overexpression inhibits the expression of dorsal transcription factors and commissural axon projections. Our results indicate that correct location of Shh expression is the key to the formation of the motor column. In conclusion, the overexpression of Shh in the spinal cord not only affects the positioning of motor neurons, but also induces abnormalities in the structure of the motor column.

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Inversion of Sonic hedgehog action on its canonical pathway by electrical activity

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1419690112 ◽

2015 ◽

Vol 112 (13) ◽

pp. 4140-4145 ◽

Cited By ~ 23

Author(s):

Yesser H. Belgacem ◽

Laura N. Borodinsky

Keyword(s):

Spinal Cord ◽

Electrical Activity ◽

Sonic Hedgehog ◽

Wide Spectrum ◽

Canonical Pathway ◽

Regulatory Mechanisms ◽

Spatiotemporal Resolution ◽

Spinal Cord Development ◽

Shh Pathway ◽

Element Binding Protein

Sonic hedgehog (Shh) is a morphogenic protein that operates through the Gli transcription factor-dependent canonical pathway to orchestrate normal development of many tissues. Because aberrant levels of Gli activity lead to a wide spectrum of diseases ranging from neurodevelopmental defects to cancer, understanding the regulatory mechanisms of Shh canonical pathway is paramount. During early stages of spinal cord development, Shh specifies neural progenitors through the canonical signaling. Despite persistence of Shh as spinal cord development progresses, Gli activity is switched off by unknown mechanisms. In this study we find that Shh inverts its action on Gli during development. Strikingly, Shh decreases Gli signaling in the embryonic spinal cord by an electrical activity- and cAMP-dependent protein kinase-mediated pathway. The inhibition of Gli activity by Shh operates at multiple levels. Shh promotes cytosolic over nuclear localization of Gli2, induces Gli2 and Gli3 processing into repressor forms, and activates cAMP-responsive element binding protein that in turn represses gli1 transcription. The regulatory mechanisms identified in this study likely operate with different spatiotemporal resolution and ensure effective down-regulation of the canonical Shh signaling as spinal cord development progresses. The developmentally regulated intercalation of electrical activity in the Shh pathway may represent a paradigm for switching from canonical to noncanonical roles of developmental cues during neuronal differentiation and maturation.

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Left-right pattern of cardiac BMP4 may drive asymmetry of the heart in zebrafish

Development ◽

10.1242/dev.124.21.4373 ◽

1997 ◽

Vol 124 (21) ◽

pp. 4373-4382 ◽

Cited By ~ 17

Author(s):

J.N. Chen ◽

F.J. van Eeden ◽

K.S. Warren ◽

A. Chin ◽

C. Nusslein-Volhard ◽

...

Keyword(s):

Spinal Cord ◽

Sonic Hedgehog ◽

Dominant Negative ◽

Heart Tube ◽

Dorsoventral Axis ◽

Spinal Cord Development ◽

Bmp4 Expression ◽

The Right ◽

Zebrafish Heart ◽

Ventral Spinal Cord

The first evident break in left-right symmetry of the primitive zebrafish heart tube is the shift in pattern of BMP4 expression from radially symmetric to left-predominant. The midline heart tube then ‘jogs’ to the left and subsequently loops to the right. We examined 279 mutations, affecting more than 200 genes, and found 21 mutations that perturb this process. Some cause BMP4 to remain radially symmetric. Others randomize the asymmetric BMP4 pattern. Retention of BMP4 symmetry is associated with failure to jog: right-predominance of the BMP4 pattern is associated with reversal of the direction of jogging and looping. Raising BMP4 diffusely throughout the heart, via sonic hedgehog injection, or the blocking of its action by injection of a dominant negative BMP4 receptor, prevent directional jogging or looping. The genes crucial to directing cardiac asymmetry include a subset of those needed for patterning the dorsoventral axis and for notochord and ventral spinal cord development. Thus, the pattern of cardiac BMP4 appears to be in the pathway by which the heart interprets lateralizing signals from the midline.

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Gbx1 and Gbx2 Are Essential for Normal Patterning and Development of Interneurons and Motor Neurons in the Embryonic Spinal Cord

Journal of Developmental Biology ◽

10.3390/jdb8020009 ◽

2020 ◽

Vol 8 (2) ◽

pp. 9

Author(s):

Desirè M. Buckley ◽

Jessica Burroughs-Garcia ◽

Sonja Kriks ◽

Mark Lewandoski ◽

Samuel T. Waters

Keyword(s):

Spinal Cord ◽

Transcription Factors ◽

Motor Neurons ◽

Molecular Mechanisms ◽

Apoptotic Cell ◽

System Development ◽

Nervous System Development ◽

Control Of Gene Expression ◽

Spinal Cord Development ◽

Ependymal Layer

The molecular mechanisms regulating neurogenesis involve the control of gene expression by transcription factors. Gbx1 and Gbx2, two members of the Gbx family of homeodomain-containing transcription factors, are known for their essential roles in central nervous system development. The expression domains of mouse Gbx1 and Gbx2 include regions of the forebrain, anterior hindbrain, and spinal cord. In the spinal cord, Gbx1 and Gbx2 are expressed in PAX2+ interneurons of the dorsal horn and ventral motor neuron progenitors. Based on their shared domains of expression and instances of overlap, we investigated the functional relationship between Gbx family members in the developing spinal cord using Gbx1−/−, Gbx2−/−, and Gbx1−/−/Gbx2−/− embryos. In situ hybridization analyses of embryonic spinal cords show upregulation of Gbx2 expression in Gbx1−/− embryos and upregulation of Gbx1 expression in Gbx2−/− embryos. Additionally, our data demonstrate that Gbx genes regulate development of a subset of PAX2+ dorsal inhibitory interneurons. While we observe no difference in overall proliferative status of the developing ependymal layer, expansion of proliferative cells into the anatomically defined mantle zone occurs in Gbx mutants. Lastly, our data shows a marked increase in apoptotic cell death in the ventral spinal cord of Gbx mutants during mid-embryonic stages. While our studies reveal that both members of the Gbx gene family are involved in development of subsets of PAX2+ dorsal interneurons and survival of ventral motor neurons, Gbx1 and Gbx2 are not sufficient to genetically compensate for the loss of one another. Thus, our studies provide novel insight to the relationship harbored between Gbx1 and Gbx2 in spinal cord development.

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An Early Developmental Marker for Radial Glia in Rat Spinal Cord

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100162648 ◽

1996 ◽

Vol 54 ◽

pp. 36-37

Author(s):

V. Kriho ◽

H.-Y. Yang ◽

C.-M. Lue ◽

N. Lieska ◽

G. D. Pappas

Keyword(s):

Spinal Cord ◽

Intermediate Filament ◽

Radial Glia ◽

Rat Spinal Cord ◽

Future Studies ◽

Spinal Cord Development ◽

Median Septum ◽

Differentiation Marker ◽

Early Developmental ◽

Developing Rat

Radial glia have been classically defined as those early glial cells that radially span their thin processes from the ventricular to the pial surfaces in the developing central nervous system. These radial glia constitute a transient cell population, disappearing, for the most part, by the end of the period of neuronal migration. Traditionally, it has been difficult to definitively identify these cells because the principal criteria available were morphologic only.Using immunofluorescence microscopy, we have previously defined a phenotype for radial glia in rat spinal cord based upon the sequential expression of vimentin, glial fibrillary acidic protein and an intermediate filament-associated protein, IFAP-70/280kD. We report here the application of another intermediate filament-associated protein, IFAP-300kD, originally identified in BHK-21 cells, to the immunofluorescence study of radial glia in the developing rat spinal cord.Results showed that IFAP-300kD appeared very early in rat spinal cord development. In fact by embryonic day 13, IFAP-300kD immunoreactivity was already at its peak and was observed in most of the radial glia which span the spinal cord from the ventricular to the subpial surfaces (Fig. 1). Interestingly, from this time, IFAP-300kD immunoreactivity diminished rapidly in a dorsal to ventral manner, so that by embryonic day 16 it was detectable only in the maturing macroglial cells in the marginal zone of the spinal cord and the dorsal median septum (Fig. 2). By birth, the spinal cord was essentially immuno-negative for this IFAP. Thus, IFAP-300kD appears to be another differentiation marker available for future studies of gliogenesis, especially for the early stages of radial glia differentiation.

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