ABSTRACT
Myelin-forming oligodendrocytes in the vertebrate nervous system co-express the transcription factor Sox10 and its paralog Sox8. While Sox10 plays crucial roles throughout all stages of oligodendrocyte development, including terminal differentiation, the loss of Sox8 results in only mild and transient perturbations. Here, we aimed to elucidate the roles and interrelationships of these transcription factors in fully differentiated oligodendrocytes and myelin maintenance in adults. For that purpose, we conducted targeted deletions of Sox10, Sox8, or both in the brains of two-month-old mice. Three weeks post-deletion, none of the resulting mouse mutants exhibited significant alterations in oligodendrocyte numbers, myelin sheath counts, myelin ultrastructure, or myelin protein levels in the corpus callosum, despite efficient gene inactivation. However, differences were observed in the myelin gene expression in mice with Sox10 or combined Sox8/Sox10 deletion. RNA-sequencing analysis on dissected corpus callosum confirmed substantial alterations in the oligodendrocyte expression profile in mice with combined deletion and more subtle changes in mice with Sox10 deletion alone. Notably, Sox8 deletion did not affect any aspects of the expression profile related to the differentiated state of oligodendrocytes or myelin integrity. These findings extend our understanding of the roles of Sox8 and Sox10 in oligodendrocytes into adulthood and have important implications for the functional relationship between the paralogs and the underlying molecular mechanisms.
Subject(s)
Cell Differentiation , Myelin Sheath , Oligodendroglia , SOXE Transcription Factors , Animals , SOXE Transcription Factors/metabolism , SOXE Transcription Factors/genetics , Oligodendroglia/metabolism , Oligodendroglia/cytology , Mice , Myelin Sheath/metabolism , Cell Differentiation/genetics , Corpus Callosum/metabolism , Mice, Knockout , SOXC Transcription Factors/metabolism , SOXC Transcription Factors/geneticsABSTRACT
The transcription factor Sox10 is an important determinant of oligodendroglial identity and influences oligodendroglial development and characteristics at various stages. Starting from RNA-seq data, we here show that the expression of several voltage-gated ion channels with known expression and important function in oligodendroglial cells depends upon Sox10. These include the Nav1.1, Cav2.2, Kv1.1, and Kir4.1 channels. For each of the four encoding genes, we found at least one regulatory region that is activated by Sox10 in vitro and at the same time bound by Sox10 in vivo. Cell-specific deletion of Sox10 in oligodendroglial cells furthermore led to a strong downregulation of all four ion channels in a mouse model and thus in vivo. Our study provides a clear functional link between voltage-gated ion channels and the transcriptional regulatory network in oligodendroglial cells. Furthermore, our study argues that Sox10 exerts at least some of its functions in oligodendrocyte progenitor cells, in myelinating oligodendrocytes, or throughout lineage development via these ion channels. By doing so, we present one way in which oligodendroglial development and properties can be linked to neuronal activity to ensure crosstalk between cell types during the development and function of the central nervous system.
Subject(s)
Oligodendroglia , SOXE Transcription Factors , SOXE Transcription Factors/metabolism , SOXE Transcription Factors/genetics , Animals , Oligodendroglia/metabolism , Oligodendroglia/cytology , Mice , Ion Channels/metabolism , Ion Channels/genetics , Transcription, Genetic , Gene Expression Regulation, Developmental , Cell Differentiation/genetics , HumansABSTRACT
Rapid information processing in the central nervous system requires the myelination of axons by oligodendrocytes. The transcription factor Sox2 and its close relative Sox3 redundantly regulate the development of myelin-forming oligodendrocytes, but little is known about the underlying molecular mechanisms. Here, we characterized the expression profile of cultured oligodendroglial cells during early differentiation and identified Bcas1, Enpp6, Zfp488 and Nkx2.2 as major downregulated genes upon Sox2 and Sox3 deletion. An analysis of mice with oligodendrocyte-specific deletion of Sox2 and Sox3 validated all four genes as downstream targets in vivo. Additional functional assays identified regulatory regions in the vicinity of each gene that are responsive to and bind both Sox proteins. Bcas1, Enpp6, Zfp488 and Nkx2.2 therefore likely represent direct target genes and major effectors of Sox2 and Sox3. Considering the preferential expression and role of these genes in premyelinating oligodendrocytes, our findings suggest that Sox2 and Sox3 impact oligodendroglial development at the premyelinating stage with Bcas1, Enpp6, Zfp488 and Nkx2.2 as their major effectors.
Subject(s)
Cell Differentiation , Homeobox Protein Nkx-2.2 , Oligodendroglia , SOXB1 Transcription Factors , Transcription Factors , Animals , Mice , Cell Differentiation/genetics , Gene Expression Regulation, Developmental , Homeodomain Proteins/metabolism , Homeodomain Proteins/genetics , Oligodendroglia/metabolism , Oligodendroglia/cytology , Phosphoric Diester Hydrolases/metabolism , Phosphoric Diester Hydrolases/genetics , SOXB1 Transcription Factors/metabolism , SOXB1 Transcription Factors/genetics , SOXC Transcription Factors/metabolism , SOXC Transcription Factors/genetics , Transcription Factors/metabolism , Transcription Factors/geneticsABSTRACT
The HMG-domain containing transcription factor Sox10 plays a crucial role in regulating Schwann cell survival and differentiation and is expressed throughout the entire Schwann cell lineage. While its importance in peripheral myelination is well established, little is known about its role in the early stages of Schwann cell development. In a search for direct target genes of Sox10 in Schwann cell precursors, the transcriptional co-repressor Tle4 was identified. At least two regions upstream of the Tle4 gene appear involved in mediating the Sox10-dependent activation. Once induced, Tle4 works in tandem with the bHLH transcriptional repressor Hes1 and exerts a dual inhibitory effect on Sox10 by preventing the Sox10 protein from transcriptionally activating maturation genes and by suppressing Sox10 expression through known enhancers of the gene. This mechanism establishes a regulatory barrier that prevents premature activation of factors involved in differentiation and myelin formation by Sox10 in immature Schwann cells. The identification of Tle4 as a critical downstream target of Sox10 sheds light on the gene regulatory network in the early phases of Schwann cell development. It unravels an elaborate regulatory circuitry that fine-tunes the timing and extent of Schwann cell differentiation and myelin gene expression.
Subject(s)
Cell Differentiation , DNA-Binding Proteins , SOXE Transcription Factors , Schwann Cells , Animals , Humans , Mice , Rats , Cell Differentiation/genetics , Co-Repressor Proteins/metabolism , Co-Repressor Proteins/genetics , Feedback, Physiological , Gene Expression Regulation , Myelin Sheath/metabolism , Schwann Cells/metabolism , Schwann Cells/cytology , SOXE Transcription Factors/metabolism , SOXE Transcription Factors/genetics , Transcription Factor HES-1/metabolism , Transcription Factor HES-1/genetics , DNA-Binding Proteins/metabolismABSTRACT
Remyelination failure in diseases like multiple sclerosis (MS) was thought to involve suppressed maturation of oligodendrocyte precursors; however, oligodendrocytes are present in MS lesions yet lack myelin production. We found that oligodendrocytes in the lesions are epigenetically silenced. Developing a transgenic reporter labeling differentiated oligodendrocytes for phenotypic screening, we identified a small-molecule epigenetic-silencing-inhibitor (ESI1) that enhances myelin production and ensheathment. ESI1 promotes remyelination in animal models of demyelination and enables de novo myelinogenesis on regenerated CNS axons. ESI1 treatment lengthened myelin sheaths in human iPSC-derived organoids and augmented (re)myelination in aged mice while reversing age-related cognitive decline. Multi-omics revealed that ESI1 induces an active chromatin landscape that activates myelinogenic pathways and reprograms metabolism. Notably, ESI1 triggered nuclear condensate formation of master lipid-metabolic regulators SREBP1/2, concentrating transcriptional co-activators to drive lipid/cholesterol biosynthesis. Our study highlights the potential of targeting epigenetic silencing to enable CNS myelin regeneration in demyelinating diseases and aging.
Subject(s)
Epigenesis, Genetic , Myelin Sheath , Oligodendroglia , Remyelination , Animals , Myelin Sheath/metabolism , Humans , Mice , Remyelination/drug effects , Oligodendroglia/metabolism , Central Nervous System/metabolism , Mice, Inbred C57BL , Rejuvenation , Induced Pluripotent Stem Cells/metabolism , Induced Pluripotent Stem Cells/drug effects , Sterol Regulatory Element Binding Protein 1/metabolism , Organoids/metabolism , Organoids/drug effects , Demyelinating Diseases/metabolism , Demyelinating Diseases/genetics , Cell Differentiation/drug effects , Small Molecule Libraries/pharmacology , Male , Regeneration/drug effects , Multiple Sclerosis/metabolism , Multiple Sclerosis/genetics , Multiple Sclerosis/drug therapy , Multiple Sclerosis/pathologyABSTRACT
The plant homeodomain finger protein Phf8 is a histone demethylase implicated by mutation in mice and humans in neural crest defects and neurodevelopmental disturbances. Considering its widespread expression in cell types of the central nervous system, we set out to determine the role of Phf8 in oligodendroglial cells to clarify whether oligodendroglial defects are a possible contributing factor to Phf8-dependent neurodevelopmental disorders. Using loss- and gain-of-function approaches in oligodendroglial cell lines and primary cell cultures, we show that Phf8 promotes the proliferation of rodent oligodendrocyte progenitor cells and impairs their differentiation to oligodendrocytes. Intriguingly, Phf8 has a strong positive impact on Olig2 expression by acting on several regulatory regions of the gene and changing their histone modification profile. Taking the influence of Olig2 levels on oligodendroglial proliferation and differentiation into account, Olig2 likely acts as an important downstream effector of Phf8 in these cells. In line with such an effector function, ectopic Olig2 expression in Phf8-deficient cells rescues the proliferation defect. Additionally, generation of human oligodendrocytes from induced pluripotent stem cells did not require PHF8 in a system that relies on forced expression of Olig2 during oligodendroglial induction. We conclude that Phf8 may impact nervous system development at least in part through its action in oligodendroglial cells.
Subject(s)
Cell Proliferation , Oligodendrocyte Transcription Factor 2 , Oligodendroglia , Transcription Factors , Oligodendroglia/metabolism , Oligodendrocyte Transcription Factor 2/metabolism , Animals , Humans , Transcription Factors/metabolism , Transcription Factors/genetics , Mice , Cell Proliferation/physiology , Cell Differentiation/physiology , Cells, Cultured , Histone Demethylases/metabolism , Histone Demethylases/genetics , Rats , Basic Helix-Loop-Helix Transcription Factors/metabolism , Basic Helix-Loop-Helix Transcription Factors/genetics , Induced Pluripotent Stem Cells/metabolismABSTRACT
Oligodendrocyte differentiation and myelination in the central nervous system are controlled and coordinated by a complex gene regulatory network that contains several transcription factors, including Zfp488 and Nkx2.2. Despite the proven role in oligodendrocyte differentiation little is known about the exact mode of Zfp488 and Nkx2.2 action, including their target genes. Here, we used overexpression of Zfp488 and Nkx2.2 in differentiating CG4 cells to identify aspects of the oligodendroglial expression profile that depend on these transcription factors. Although both transcription factors are primarily described as repressors, the detected changes argue for an additional function as activators. Among the genes activated by both Zfp488 and Nkx2.2 was the G protein-coupled receptor Gpr37 that is important during myelination. In agreement with a positive effect on Gpr37 expression, downregulation of the G protein-coupled receptor was observed in Zfp488- and in Nkx2.2-deficient oligodendrocytes in the mouse. We also identified several potential regulatory regions of the Gpr37 gene. Although Zfp488 and Nkx2.2 both bind to one of the regulatory regions downstream of the Gpr37 gene in vivo, none of the regulatory regions was activated by either transcription factor alone. Increased activation by Zfp488 or Nkx2.2 was only observed in the presence of Sox10, a transcription factor continuously present in oligodendroglial cells. Our results argue that both Zfp488 and Nkx2.2 also act as transcriptional activators during oligodendrocyte differentiation and cooperate with Sox10 to allow the expression of Gpr37 as a modulator of the myelination process.
Subject(s)
Cell Differentiation , Homeobox Protein Nkx-2.2 , Homeodomain Proteins , Oligodendroglia , Receptors, G-Protein-Coupled , SOXE Transcription Factors , Transcription Factors , Animals , Female , Male , Mice , Cell Differentiation/physiology , Homeodomain Proteins/metabolism , Homeodomain Proteins/genetics , Myelin Sheath/metabolism , Oligodendroglia/metabolism , Receptors, G-Protein-Coupled/metabolism , Receptors, G-Protein-Coupled/genetics , SOXE Transcription Factors/metabolism , SOXE Transcription Factors/genetics , Transcription Factors/metabolism , Transcription Factors/geneticsABSTRACT
Genome-wide association studies identified a single nucleotide polymorphism (SNP) downstream of the transcription factor Sox8, associated with an increased risk of multiple sclerosis (MS). Sox8 is known to influence oligodendrocyte terminal differentiation and is involved in myelin maintenance by mature oligodendrocytes. The possible link of a Sox8 related SNP and MS risk, along with the role of Sox8 in oligodendrocyte physiology prompted us to investigate its relevance during de- and remyelination using the cuprizone model. Sox8-/- mice and wildtype littermates received a cuprizone diet for 5 weeks (wk). Sox8-/- mice showed reduced motor performance and weight compared to wildtype controls. Brains were histologically analysed at the maximum of demyelination (wk 5) and on two time points during remyelination (wk 5.5 and wk 6) for oligodendroglial, astroglial, microglial and myelin markers. We identified reduced proliferation of oligodendrocyte precursor cells at wk 5 as well as reduced numbers of mature oligodendrocytes in Sox8-/- mice at wk 6. Moreover, analysis of myelin markers revealed a delay in remyelination in the Sox8-/- group, demonstrating the potential importance of Sox8 in remyelination processes. Our findings present, for the first time, compelling evidence of a significant role of Sox8 in the context of a disease model.
Subject(s)
Demyelinating Diseases , Multiple Sclerosis , Remyelination , Mice , Animals , Cuprizone/toxicity , Demyelinating Diseases/chemically induced , Demyelinating Diseases/genetics , Demyelinating Diseases/pathology , Cell Differentiation , Genome-Wide Association Study , Oligodendroglia , Myelin Sheath/pathology , Multiple Sclerosis/chemically induced , Multiple Sclerosis/genetics , Multiple Sclerosis/pathology , Mice, Inbred C57BL , Disease Models, Animal , SOXE Transcription Factors/geneticsABSTRACT
Oligodendrocyte development is accompanied by defined changes in the state of chromatin that are brought about by chromatin remodeling complexes. Many such remodeling complexes exist, but only a few have been studied for their impact on oligodendrocytes as the myelin-forming cells of the central nervous system. To define the role of the PBAF remodeling complex, we focused on Pbrm1 as an essential subunit of the PBAF complex and specifically deleted it in the oligodendrocyte lineage at different times of development in the mouse. Deletion in late oligodendrocyte progenitor cells did not lead to substantial changes in the ensuing differentiation and myelination processes. However, when Pbrm1 loss had already occurred in oligodendrocyte progenitor cells shortly after their specification, fewer cells entered the pre-myelinating state. The reduction in pre-myelinating cells later translated into a comparable reduction in myelinating oligodendrocytes. We conclude that Pbrm1 and, by inference, the activity of the PBAF complex is specifically required at the transition from oligodendrocyte progenitor to pre-myelinating oligodendrocyte and ensures the generation of normal numbers of myelinating oligodendrocytes.
Subject(s)
Myelin Sheath , Oligodendroglia , Animals , Mice , Cell Differentiation/physiology , Central Nervous System , Myelin Sheath/physiology , Stem CellsABSTRACT
The cranial neural crest plays a fundamental role in orofacial development and morphogenesis. Accordingly, mutations with impact on the cranial neural crest and its development lead to orofacial malformations such as cleft lip and palate. As a pluripotent and dynamic cell population, the cranial neural crest undergoes vast transcriptional and epigenomic alterations throughout the formation of facial structures pointing to an essential role of factors regulating chromatin state or transcription levels. Using CRISPR/Cas9-guided genome editing and conditional mutagenesis in the mouse, we here show that inactivation of Kat5 or Ep400 as the two essential enzymatic subunits of the Tip60/Ep400 chromatin remodeling complex severely affects carbohydrate and amino acid metabolism in cranial neural crest cells. The resulting decrease in protein synthesis, proliferation and survival leads to a drastic reduction of cranial neural crest cells early in fetal development and a loss of most facial structures in the absence of either protein. Following heterozygous loss of Kat5 in neural crest cells palatogenesis was impaired. These findings point to a decisive role of the Tip60/Ep400 chromatin remodeling complex in facial morphogenesis and lead us to conclude that the orofacial clefting observed in patients with heterozygous KAT5 missense mutations is at least in part due to disturbances in the cranial neural crest.
Subject(s)
Cleft Lip , Cleft Palate , Animals , Mice , Chromatin Assembly and Disassembly , Cleft Lip/genetics , Cleft Palate/genetics , DNA Helicases/genetics , DNA Helicases/metabolism , DNA-Binding Proteins , Neural Crest/metabolism , Skull , Transcription Factors/metabolismABSTRACT
The high-mobility-group domain-containing transcription factor Sox9 confers glial competence to neuroepithelial precursors in the developing central nervous system and is an important determinant of astroglial and oligodendroglial specification. In oligodendroglial cells, it remains expressed in oligodendrocyte progenitor cells (OPCs) of the developing nervous system, but is shut off in differentiating oligodendrocytes as well as in OPCs that persist in the adult nervous system. To better understand the role of Sox9 in OPCs, we generated mouse models that allowed oligodendroglial expression of a Sox9 transgene during development or in the adult. With transgene expression beginning in the last trimester of pregnancy, the number of OPCs increased dramatically, followed by comparable gains in the number of pre-myelinating and myelinating oligodendrocytes as assessed by marker gene expression. This argues that Sox9 boosts oligodendrogenesis during ontogenetic development at all stages, including terminal oligodendrocyte differentiation. When Sox9 transgene expression started in the adult, many transgene-expressing OPCs failed to maintain their progenitor cell identity and instead converted into myelinating oligodendrocytes. As infrequent and inefficient differentiation of adult OPCs is one of the main obstacles to effective remyelination in demyelinating diseases such as Multiple Sclerosis, increased Sox9 levels in adult OPCs may substantially increase their remyelination capacity.
Subject(s)
Multiple Sclerosis , Oligodendroglia , Mice , Animals , Oligodendroglia/metabolism , Cell Differentiation/physiology , Neuroglia/metabolism , Multiple Sclerosis/metabolism , Stem Cells/metabolism , Myelin Sheath/metabolismABSTRACT
Differentiated oligodendrocytes produce myelin and thereby ensure rapid nerve impulse conduction and efficient information processing in the vertebrate central nervous system. The Krüppel-like transcription factor KLF9 enhances oligodendrocyte differentiation in culture, but appears dispensable in vivo. Its mode of action and role within the oligodendroglial gene regulatory network are unclear. Here we show that KLF9 shares its expression in differentiating oligodendrocytes with the closely related KLF13 protein. Both KLF9 and KLF13 bind to regulatory regions of genes that are important for oligodendrocyte differentiation and equally recognized by the central differentiation promoting transcription factors SOX10 and MYRF. KLF9 and KLF13 physically interact and synergistically activate oligodendrocyte-specific regulatory regions with SOX10 and MYRF. Similar to KLF9, KLF13 promotes differentiation and myelination in primary oligodendroglial cultures. Oligodendrocyte differentiation is also altered in KLF13-deficient mice as demonstrated by a transiently reduced myelin gene expression during the first postnatal week. Considering mouse phenotypes, the similarities in expression pattern and genomic binding and the behaviour in functional assays, KLF9 and KLF13 are important and largely redundant components of the gene regulatory network in charge of oligodendrocyte differentiation and myelination.
Subject(s)
Kruppel-Like Transcription Factors , Myelin Sheath , Oligodendroglia , SOXE Transcription Factors , Animals , Mice , Cell Differentiation/genetics , Gene Expression , Kruppel-Like Transcription Factors/genetics , Kruppel-Like Transcription Factors/metabolism , Myelin Sheath/genetics , Myelin Sheath/metabolism , Oligodendroglia/metabolism , SOXE Transcription Factors/genetics , SOXE Transcription Factors/metabolismABSTRACT
In oligodendrocytes of the vertebrate central nervous system a complex network of transcriptional regulators is required to ensure correct and timely myelination of neuronal axons. Here we identify Zfp276, the only mammalian ZAD-domain containing zinc finger protein, as a transcriptional regulator of oligodendrocyte differentiation and central myelination downstream of Sox10. In the central nervous system, Zfp276 is exclusively expressed in mature oligodendrocytes. Oligodendroglial deletion of Zfp276 led to strongly reduced expression of myelin genes in the early postnatal mouse spinal cord. Retroviral overexpression of Zfp276 in cultured oligodendrocyte precursor cells induced precocious expression of maturation markers and myelin genes, further supporting its role in oligodendroglial differentiation. On the molecular level, Zfp276 directly binds to and represses Sox10-dependent gene regulatory regions of immaturity factors and functionally interacts with the transcriptional repressor Zeb2 to enable fast transition of oligodendrocytes to the myelinating stage.
Subject(s)
Oligodendroglia , Spinal Cord/cytology , Transcription Factors , Animals , Cell Differentiation , Mice , Myelin Sheath/physiology , Neurogenesis , Oligodendroglia/cytology , Oligodendroglia/metabolism , Spinal Cord/metabolism , Stem Cells , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
Myelin sheath formation in the peripheral nervous system and the ensuing saltatory conduction rely on differentiated Schwann cells. We have previously shown that transition of Schwann cells from an immature into a differentiated state requires Brg1 that serves as the central energy generating subunit in two related SWI/SNF-type chromatin remodelers, the BAF and the PBAF complex. Here we used conditional deletion of Pbrm1 to selectively interfere with the PBAF complex in Schwann cells. Despite efficient loss of Pbrm1 early during lineage progression, we failed to detect any substantial alterations in the number, proliferation or survival of immature Schwann cells as well as in their rate and timing of terminal differentiation. As a consequence, postnatal myelin formation in peripheral nerves appeared normal. There were no inflammatory alterations in the nerve or other signs of a peripheral neuropathy. We conclude from our study that Pbrm1 and very likely the PBAF complex are dispensable for proper Schwann cell development and that Schwann cell defects previously observed upon Brg1 deletion are mostly attributable to altered or absent function of the BAF complex.
Subject(s)
Cell Differentiation/genetics , Chromosomal Proteins, Non-Histone/physiology , DNA-Binding Proteins/physiology , Schwann Cells/physiology , Transcription Factors/physiology , Animals , Cell Lineage/genetics , Cell Proliferation/genetics , Cell Survival/genetics , DNA Helicases/genetics , Gene Deletion , Mice , Myelin Sheath/physiology , Nuclear Proteins/genetics , Peripheral Nerves/physiology , Transcription Factors/geneticsABSTRACT
Recently, oligodendrocytes (Ol) have been attributed potential immunomodulatory effects. Yet, the exact mode of interaction with pathogenic CNS infiltrating lymphocytes remains unclear. Here, we attempt to dissect mechanisms of Ol modulation during neuroinflammation and characterize the interaction of Ol with pathogenic T cells. RNA expression analysis revealed an upregulation of immune-modulatory genes and adhesion molecules (AMs), ICAM-1 and VCAM-1, in Ol when isolated from mice undergoing experimental autoimmune encephalomyelitis (EAE). To explore whether AMs are involved in the interaction of Ol with infiltrating T cells, we performed co-culture studies on mature Ol and Th1 cells. Live cell imaging analysis showed direct interaction between both cell types. Eighty percentage of Th1 cells created contacts with Ol that lasted longer than 15 min, which may be regarded as physiologically relevant. Exposure of Ol to Th1 cells or their supernatant resulted in a significant extension of Ol processes, and upregulation of AMs as well as other immunomodulatory genes. Our observations indicate that blocking of oligodendroglial ICAM-1 can reduce the number of Th1 cells initially contacting the Ol. These results suggest that AMs may play a role in the interaction between Ol and Th1 cells. We identified Ol interacting with CD4+ cells in vivo in spinal cord tissue of EAE diseased mice indicating that our in vitro findings are of interest to further scientific research in this field. Further characterization and understanding of Ol interaction with infiltrating cells may lead to new therapeutic strategies enhancing Ol protection and remyelination potential. Oligodendrocytes regulate immune modulatory genes and adhesion molecules during autoimmune neuroinflammation Oligodendrocytes interact with Th1 cells in vitro in a physiologically relevant manner Adhesion molecules may be involved in Ol-Th1 cell interaction.
Subject(s)
Encephalomyelitis, Autoimmune, Experimental , Intercellular Adhesion Molecule-1/metabolism , Animals , Encephalomyelitis, Autoimmune, Experimental/pathology , Intercellular Adhesion Molecule-1/genetics , Mice , Mice, Inbred C57BL , Neuroinflammatory Diseases , Oligodendroglia/metabolismABSTRACT
Cortical parvalbumin-expressing (Pvalb+) neurons provide robust inhibition to neighboring pyramidal neurons, crucial for the proper functioning of cortical networks. This class of inhibitory neurons undergoes extensive synaptic formation and maturation during the first weeks after birth and continue to dynamically maintain their synaptic output throughout adulthood. While several transcription factors, such as Nkx2-1, Lhx6, and Sox6, are known to be necessary for the differentiation of progenitors into Pvalb+ neurons, which transcriptional programs underlie the postnatal maturation and maintenance of Pvalb+ neurons' innervation and synaptic function remains largely unknown. Because Sox6 is continuously expressed in Pvalb+ neurons until adulthood, we used conditional knock-out strategies to investigate its putative role in the postnatal maturation and synaptic function of cortical Pvalb+ neurons in mice of both sexes. We found that early postnatal loss of Sox6 in Pvalb+ neurons leads to failure of synaptic bouton growth, whereas later removal in mature Pvalb+ neurons in the adult causes shrinkage of already established synaptic boutons. Paired recordings between Pvalb+ neurons and pyramidal neurons revealed reduced release probability and increased failure rate of Pvalb+ neurons' synaptic output. Furthermore, Pvalb+ neurons lacking Sox6 display reduced expression of full-length tropomyosin-receptor kinase B (TrkB), a key modulator of GABAergic transmission. Once re-expressed in neurons lacking Sox6, TrkB was sufficient to rescue the morphologic synaptic phenotype. Finally, we showed that Sox6 mRNA levels were increased by motor training. Our data thus suggest a constitutive role for Sox6 in the maintenance of synaptic output from Pvalb+ neurons into adulthood.SIGNIFICANCE STATEMENT Cortical parvalbumin-expressing (Pvalb+) inhibitory neurons provide robust inhibition to neighboring pyramidal neurons, crucial for the proper functioning of cortical networks. These inhibitory neurons undergo extensive synaptic formation and maturation during the first weeks after birth and continue to dynamically maintain their synaptic output throughout adulthood. However, it remains largely unknown which transcriptional programs underlie the postnatal maturation and maintenance of Pvalb+ neurons. Here, we show that the transcription factor Sox6 cell-autonomously regulates the synaptic maintenance and output of Pvalb+ neurons until adulthood, leaving unaffected other maturational features of this neuronal population.
Subject(s)
Cerebral Cortex/metabolism , Neurons/metabolism , Parvalbumins/biosynthesis , SOXD Transcription Factors/biosynthesis , Synapses/metabolism , Animals , Animals, Newborn , Cerebral Cortex/cytology , Female , Gene Knock-In Techniques , Male , Mice , Mice, Transgenic , Organ Culture Techniques , Parvalbumins/genetics , SOXD Transcription Factors/genetics , Synapses/geneticsABSTRACT
The transcription factors Olig2 and Sox10 jointly define oligodendroglial identity. Because of their continuous presence during development and in the differentiated state they shape the oligodendroglial regulatory network at all times. In this review, we exploit their eminent role and omnipresence to elaborate the central principles that organize the gene regulatory network in oligodendrocytes in such a way that it preserves its identity, but at the same time allows defined and stimulus-dependent changes that result in an ordered lineage progression, differentiation, and myelination. For this purpose, we outline the multiple functional and physical interactions and intricate cross-regulatory relationships with other transcription factors, such as Hes5, Id, and SoxD proteins, in oligodendrocyte precursors and Tcf7l2, Sip1, Nkx2.2, Zfp24, and Myrf during differentiation and myelination, and interpret them in the context of the regulatory network.
Subject(s)
Oligodendrocyte Transcription Factor 2/metabolism , Oligodendroglia , SOXE Transcription Factors , Cell Differentiation , Gene Expression Regulation , Neurogenesis , Oligodendroglia/metabolism , SOXE Transcription Factors/genetics , SOXE Transcription Factors/metabolism , Transcription Factors/genetics , Transcription Factors/metabolismABSTRACT
The three SoxD proteins, Sox5, Sox6 and Sox13, represent closely related transcription factors with important roles during development. In the developing nervous system, SoxD proteins have so far been primarily studied in oligodendroglial cells and in interneurons of brain and spinal cord. In oligodendroglial cells, Sox5 and Sox6 jointly maintain the precursor state, interfere with terminal differentiation, and thereby ensure the proper timing of myelination in the central nervous system. Here we studied the role of SoxD proteins in Schwann cells, the functional counterpart of oligodendrocytes in the peripheral nervous system. We show that Schwann cells express Sox5 and Sox13 but not Sox6. Expression was transient and ceased with the onset of terminal differentiation. In mice with early Schwann cell-specific deletion of both Sox5 and Sox13, embryonic Schwann cell development was not substantially affected and progressed normally into the promyelinating stage. However, there was a mild and transient delay in the myelination of the peripheral nervous system of these mice. We therefore conclude that SoxD proteins-in stark contrast to their action in oligodendrocytes-promote differentiation and myelination in Schwann cells.
Subject(s)
Myelin Sheath/metabolism , Neurogenesis/genetics , Peripheral Nervous System/growth & development , Peripheral Nervous System/metabolism , SOXD Transcription Factors/deficiency , Schwann Cells/metabolism , Animals , Autoantigens/genetics , Biomarkers , Gene Deletion , Gene Expression , Immunohistochemistry , Mice , Multigene Family , Myelin Sheath/ultrastructure , Organ Specificity , SOXD Transcription Factors/genetics , Schwann Cells/ultrastructureABSTRACT
Transcription factor 4 (TCF4) is a crucial regulator of neurodevelopment and has been linked to the pathogenesis of autism, intellectual disability and schizophrenia. As a class I bHLH transcription factor (TF), it is assumed that TCF4 exerts its neurodevelopmental functions through dimerization with proneural class II bHLH TFs. Here, we aim to identify TF partners of TCF4 in the control of interhemispheric connectivity formation. Using a new bioinformatic strategy integrating TF expression levels and regulon activities from single cell RNA-sequencing data, we find evidence that TCF4 interacts with non-bHLH TFs and modulates their transcriptional activity in Satb2+ intercortical projection neurons. Notably, this network comprises regulators linked to the pathogenesis of neurodevelopmental disorders, e.g. FOXG1, SOX11 and BRG1. In support of the functional interaction of TCF4 with non-bHLH TFs, we find that TCF4 and SOX11 biochemically interact and cooperatively control commissure formation in vivo, and regulate the transcription of genes implicated in this process. In addition to identifying new candidate interactors of TCF4 in neurodevelopment, this study illustrates how scRNA-Seq data can be leveraged to predict TF networks in neurodevelopmental processes.