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

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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Zebrafish Models of Autosomal Recessive Ataxias

Cells ◽

10.3390/cells10040836 ◽

2021 ◽

Vol 10 (4) ◽

pp. 836

Author(s):

Ana Quelle-Regaldie ◽

Daniel Sobrido-Cameán ◽

Antón Barreiro-Iglesias ◽

María Jesús Sobrido ◽

Laura Sánchez

Keyword(s):

Animal Models ◽

Autosomal Recessive ◽

Molecular Mechanisms ◽

System Development ◽

Rapid Development ◽

Nervous System Development ◽

Central Nervous System Development ◽

Cellular Processes ◽

Recessive Disorders

Autosomal recessive ataxias are much less well studied than autosomal dominant ataxias and there are no clearly defined systems to classify them. Autosomal recessive ataxias, which are characterized by neuronal and multisystemic features, have significant overlapping symptoms with other complex multisystemic recessive disorders. The generation of animal models of neurodegenerative disorders increases our knowledge of their cellular and molecular mechanisms and helps in the search for new therapies. Among animal models, the zebrafish, which shares 70% of its genome with humans, offer the advantages of being small in size and demonstrating rapid development, making them optimal for high throughput drug and genetic screening. Furthermore, embryo and larval transparency allows to visualize cellular processes and central nervous system development in vivo. In this review, we discuss the contributions of zebrafish models to the study of autosomal recessive ataxias characteristic phenotypes, behavior, and gene function, in addition to commenting on possible treatments found in these models. Most of the zebrafish models generated to date recapitulate the main features of recessive ataxias.

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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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Analysis of high PSA N-CAM expression during mammalian spinal cord and peripheral nervous system development

Development ◽

10.1242/dev.112.1.69 ◽

1991 ◽

Vol 112 (1) ◽

pp. 69-82 ◽

Cited By ~ 2

Author(s):

S. Boisseau ◽

J. Nedelec ◽

V. Poirier ◽

G. Rougon ◽

M. Simonneau

Keyword(s):

Spinal Cord ◽

Neural Crest ◽

Dorsal Root Ganglia ◽

Dorsal Root ◽

Developmental Stages ◽

System Development ◽

Nervous System Development ◽

Homogeneous Distribution ◽

Total N

Using a monoclonal antibody that recognizes specifically a high polysialylated form of N-CAM (high PSA N-CAM), the temporal and spatial expression of this molecule was studied in developing spinal cord and neural crest derivatives of mouse truncal region. Temporal expression was analyzed on immunoblots of spinal cord and dorsal root ganglia (DRGs) extracts microdissected at different developmental stages. Analysis of the ratio of high PSA N-CAM to total N-CAM indicated that sialylation and desialylation are independently regulated from the expression of polypeptide chains of N-CAM. Motoneurons, dorsal root ganglia cells and commissural neurons present a homogeneous distribution of high PSA N-CAMs on both their cell bodies and their neurites. Sialylation of N-CAM can occur in neurons after their aggregation in peripheral ganglia as demonstrated for dorsal root ganglia at E12. Furthermore, peripheral ganglia express different levels of high PSA N-CAM. With in vitro models using mouse neural crest cells, we found that expression of high PSA N-CAM was restricted to cells presenting an early neuronal phenotype, suggesting a common regulation for the expression of high PSA N-CAM molecules, neurofilament proteins and sodium channels. Using perturbation experiments with endoneuraminidase, we confirmed that high PSA N-CAM molecules are involved in fasciculation and neuritic growth when neurons derived from neural crest grow on collagen substrata. However, we demonstrated that these two parameters do not appear to depend on high PSA N-CAM molecules when cells were grown on a fibronectin substratum, indicating the existence of a hierarchy among adhesion molecules.

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Engrailed-1 and netrin-1 regulate axon pathfinding by association interneurons that project to motor neurons

Development ◽

10.1242/dev.126.19.4201 ◽

1999 ◽

Vol 126 (19) ◽

pp. 4201-4212 ◽

Cited By ~ 4

Author(s):

H. Saueressig ◽

J. Burrill ◽

M. Goulding

Keyword(s):

Spinal Cord ◽

Motor Neurons ◽

Molecular Mechanisms ◽

Axon Growth ◽

Cell Types ◽

Second Phase ◽

Axon Pathfinding ◽

Cell Type Specific ◽

Embryonic Spinal Cord ◽

Ventrolateral Funiculus

During early development, multiple classes of interneurons are generated in the spinal cord including association interneurons that synapse with motor neurons and regulate their activity. Very little is known about the molecular mechanisms that generate these interneuron cell types, nor is it known how axons from association interneurons are guided toward somatic motor neurons. By targeting the axonal reporter gene τ-lacZ to the En1 locus, we show the cell-type-specific transcription factor Engrailed-1 (EN1) defines a population of association neurons that project locally to somatic motor neurons. These EN1 interneurons are born early and their axons pioneer an ipsilateral longitudinal projection in the ventral spinal cord. The EN1 interneurons extend axons in a stereotypic manner, first ventrally, then rostrally for one to two segments where their axons terminate close to motor neurons. We show that the growth of EN1 axons along a ventrolateral pathway toward motor neurons is dependent on netrin-1 signaling. In addition, we demonstrate that En1 regulates pathfinding and fasciculation during the second phase of EN1 axon growth in the ventrolateral funiculus (VLF); however, En1 is not required for the early specification of ventral interneuron cell types in the embryonic spinal cord.

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Groucho/TLE opposes axial to hypaxial motor neuron development

10.1101/2020.03.10.986323 ◽

2020 ◽

Author(s):

Adèle Salin-Cantegrel ◽

Rola Dali ◽

Jae Woong Wang ◽

Marielle Beaulieu ◽

Mira Deshmukh ◽

...

Keyword(s):

Spinal Cord ◽

Motor Neuron ◽

Motor Neurons ◽

Molecular Mechanisms ◽

List Type ◽

Neuron Development ◽

In Ovo ◽

Motor Circuits ◽

Axial Muscles ◽

Muscle Innervation

ABSTRACTSpinal cord motor neuron diversity and the ensuing variety of motor circuits allow for the processing of elaborate muscular behaviours such as body posture and breathing. Little is known, however, about the molecular mechanisms behind the specification of axial and hypaxial motor neurons controlling postural and respiratory functions respectively. Here we show that the Groucho/TLE (TLE) transcriptional corepressor is a multi-step regulator of axial and hypaxial motor neuron diversification in the developing spinal cord. TLE first promotes axial motor neuron specification at the expense of hypaxial identity by cooperating with non-canonical WNT5A signalling within the motor neuron progenitor domain. TLE further acts during post-mitotic motor neuron diversification to promote axial motor neuron topology and axonal connectivity whilst suppressing hypaxial traits. These findings provide evidence for essential and sequential roles of TLE in the spatial and temporal coordination of events regulating the development of motor neurons influencing posture and controlling respiration.HIGHLIGHTSGroucho/TLE mediates non-canonical WNT signalling in developing motor neuronsNon canonical WNT:TLE pathway regulates thoracic motor neuron diversificationTLE promotes axial while inhibiting hypaxial motor neuron developmentTLE influences developing motor neuron topology and muscle innervationIN BRIEFSalin-Cantegrel et al use in ovo engineered approaches to show that a non-canonical WNT:TLE pathway coordinates temporally and spatially separated elements of motor neuron diversification, repressing hypaxial motor neuron development to promote the axial fate.GRAPHICAL ABSTRACTTLE contribution to the development of thoracic somatic motor columnsProgenitor cells in the ventral pMN domain are exposed to higher concentrations of non-canonical WNTs and express more TLE. Cooperation of non-canonical WNTs and TLE renders ventral pMN progenitors refractory to a respiratory MN fate, thereby contributing to the separation of MMC and RMC MN lineages. Differentiating MNs that maintain high TLE expression also maintain LHX3 expression, adopt axial motor neuron topology and connect to axial muscles. TLE activity in differentiating MMC MNs prevents the acquisition of respiratory MN topology and innervation traits.

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Differing strategies used by motor neurons and glia to achieve robust development of an adult neuropil in Drosophila

10.1101/149229 ◽

2017 ◽

Author(s):

Jonathan Enriquez ◽

Laura Quintana Rio ◽

Richard Blazeski ◽

Carol Mason ◽

Richard S. Mann

Keyword(s):

Stem Cells ◽

Nervous System ◽

Birth Order ◽

Motor Neurons ◽

Neural Circuits ◽

System Development ◽

Cell Types ◽

Nervous System Development ◽

Factor Code ◽

Individual Motor

SummaryIn both vertebrates and invertebrates, neurons and glia are generated in a stereotyped order from dedicated progenitors called neural stem cells, but the purpose of invariant lineages is not understood. Here we show that three of the stem cells that produce leg motor neurons in Drosophila also generate a specialized subset of glia, the neuropil glia, which wrap and send processes into the neuropil where motor neuron dendrites arborize. The development of the neuropil glia and leg motor neurons is highly coordinated. However, although individual motor neurons have a stereotyped birth order and transcription factor code, both the number and individual morphologies of the glia born from these lineages are highly plastic, even though the final structure they contribute to is highly stereotyped. We suggest that the shared lineages of these two cell types facilitates the assembly of complex neural circuits, and that the two different birth order strategies – hardwired for motor neurons and flexible for glia – are important for robust nervous system development and homeostasis.

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Decoding molecular markers and transcriptional circuitry of naive and primed states of human pluripotency

10.1101/2020.04.17.046037 ◽

2020 ◽

Author(s):

Arindam Ghosh ◽

Anup Som

Keyword(s):

Transcription Factors ◽

Molecular Mechanisms ◽

System Development ◽

Enrichment Analysis ◽

Pathway Enrichment Analysis ◽

List Type ◽

Metabolic Processes ◽

Primed State

ABSTRACTPluripotent stem cells (PSCs) have been observed to occur in two distinct states — naive and primed. Both naive and primed state PSCs can give rise to tissues of all the three germ layers in vitro but differ in their potential to generate germline chimera in vivo. Understanding the molecular mechanisms that govern these two states of pluripotency in human can open up a plethora of opportunities for studying early embryonic development and in biomedical applications. In this work, we use weighted gene co-expression network (WGCN) approach to identify the key molecular makers and their interactions that define the two distinct pluripotency states. Signed-hybrid WGCN was reconstructed from transcriptomic data (RNA-seq) of naive and primed state pluripotent samples. Our analysis revealed two sets of genes that are involved in establishment and maintenance of naive (4791 genes) and primed (5066 genes) states. The naive state genes were found to be enriched for biological processes and pathways related to metabolic processes while primed state genes were associated with system development. Further, we identified the top 10% genes by intra-modular connectivity as hubs and the hub transcription factors for each group, thus providing a three-tier list of genes associated with naive and primed states of pluripotency in human.HIGHLIGHTSWeighted gene co-expression network analysis (WGCNA) identified 4791 and 5066 genes to be involved in naive and primed states of human pluripotency respectively.Functional and pathway enrichment analysis revealed the naive genes were mostly related to metabolic processes and primed genes to system development.The top 10% genes based on intra-modular connectivity from each group were defined as hubs.Identified 52 and 33 transcription factors among the naive and primed module hubs respectively.The transcription factors might play a switch on-off mechanism in induction of the two pluripotent states.

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Systems pathology analysis identifies neurodegenerative nature of age-related retinal diseases

10.1101/248088 ◽

2018 ◽

Author(s):

Tiina Öhman ◽

Fitsum Tamene ◽

Helka Göös ◽

Sirpa Loukovaara ◽

Markku Varjosalo

Keyword(s):

Molecular Mechanisms ◽

System Development ◽

Fibrous Tissue ◽

Nervous System Development ◽

Public Health Issue ◽

Retinal Diseases ◽

Label Free ◽

Systems Pathology ◽

Age Related ◽

Vitreoretinal Diseases

AbstractAging is a phenomenon associated with profound medical implications. Idiopathic epiretinal membrane (iEMR) and macular hole (MH) are the major vision-threatening vitreoretinal diseases affecting millions of aging people globally, making these conditions an important public health issue. The iERM is characterized by fibrous tissue developing on the surface of the macula, leading to biomechanical and biochemical macular damage. MH is a small breakage in the macula associated with many ocular conditions. Although several individual factors and pathways are suggested, a systems pathology level understanding of the molecular mechanisms underlying these disorders is lacking. Therefore, we performed mass spectrometry based label-free quantitative proteomics analysis of the vitreous proteomes from patients with iERM (n=26) and MH (n=21) to identify the key proteins as well as the multiple interconnected biochemical pathways contributing to the development of these diseases. We identified a total of 1014 unique proteins, of which many were linked to inflammation and complement cascade, revealing the inflammational processes in retinal diseases. Additionally, we detected a profound difference in proteomes of the iEMR and MH compared to the non-proliferative diabetic retinopathy. A large number of neuronal proteins were present at higher levels in iERM and MH vitreous, including neuronal adhesion molecules, nervous system development proteins and signalling molecules. This points toward the important role of neurodegeneration component in the pathogenesis of age-related vitreoretinal diseases. Despite of marked similarities, several unique vitreous proteins were identified in both iERM and MH conditions, providing a candidate targets for diagnostic and new therapeutic approaches. Identification of previously reported and novel proteins in human vitreous humor from patient with iERM and MH provide renewed understanding of the pathogenesis of age-related vitreoretinal diseases.

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A Gene-Targeted Mouse Model for Bone Marrow Failure Syndrome.

Blood ◽

10.1182/blood.v106.11.4235.4235 ◽

2005 ◽

Vol 106 (11) ◽

pp. 4235-4235

Author(s):

Masataka Kasai ◽

Yuko Fukuda ◽

Reiko Ishida

Keyword(s):

Bone Marrow ◽

Transcription Factors ◽

Molecular Mechanisms ◽

Bone Marrow Failure ◽

Myeloid Cells ◽

Pcr Analysis ◽

Mrna Levels ◽

Control Of Gene Expression ◽

Wild Mice ◽

Immature Myeloid Cells

Abstract Bone marrow failure is a disease syndrome characterized by dysfunction of bone marrow to produce mature blood cells. However, molecular mechanisms causing the disease syndromes remain remarkably obscure. We generated mice homozygous for an inactivating mutation of the Translin gene. Most of the aged mutant mice (Translin−/−) were found to exhibit progressive bone marrow dysfunction manifested by a reduction in immature myeloid cells and erythroblasts, and eventually developed marked splenomegaly, with up to 30-fold elevation in weight. Histological examination of enlarged spleens revealed extramedullary hematopoiesis, prominent expansion of the red pulp areas with an increase in the number of mature granulocytes and a marked lack of immature myeloid cells. Furthermore, these mice also featured complete loss of immature myeloid cells and erythroblasts in bone marrow. On the other hand, an increase in the number of reticulocytes (over 10 %) and unusual appearance of metamyelocytes and orthochromatic erythroblasts were seen in peripheral blood. A cascade of the lineage-restricted transcription factors is known to determine developmental decisions regarding hematopoiesis. How levels of transcription factors are translated into a decision to control lineage commitment is an intriguing question in hematopoiesis which remains to be explored. Therefore, we considered the bone marrow failure in aged Translin−/− might be due to decreased expression of the Ets family transcription factor PU.1 that has previously been suggested to be essential for myeloid development. However, quantitative RT-PCR analysis showed PU.1 mRNA to be expressed at equivalent levels in bone marrows of mutant and wild mice. In contrast, our data indicated a sharp reduction of the mRNA levels of the basic helix-loop-helix (bHLH) protein, E2A and its dimerization partner, TAL1, suggesting a contribution of E47/TAL heterodimer having distinctive DNA-binding properties for fine tune control of gene expression during hematopoiesis. In conclusion, the present studies demonstrated that expression levels of Translin are crucial to the bone marrow’s functional ability, and that our findings will shed light on the molecular events involved in bone marrow failure syndromes.

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