DLX1 and the NuRD complex cooperate in enhancer decommissioning and transcriptional repression

NOTCH, ERK, and SHH signaling respectively control the fate determination of cortical glia and olfactory bulb interneurons

During cortical development, radial glial cells (neural stem cells) initially are neurogenic, generating intermediate progenitor cells that exclusively produce glutamatergic pyramidal neurons. Next, radial glial cells generate tripotential intermediate progenitor cells (Tri-IPCs) that give rise to cortical astrocytes and oligodendrocytes, and olfactory bulb interneurons. The molecular mechanisms underlying the transition from cortical neurogenesis to gliogenesis, and the subsequent fate determination of cortical astrocytes, oligodendrocytes, and olfactory bulb interneurons, remain unclear. Here, we report that extracellular signal-regulated kinase (ERK) signaling plays a fundamental role in promoting cortical gliogenesis and the generation of Tri-IPCs. Additionally, sonic hedgehog-smoothened-glioma-associated oncogene homolog (SHH-SMO-GLI) activator signaling has an auxiliary function to ERK during these processes. We further demonstrate that, from Tri-IPCs, NOTCH signaling is crucial for the fate determination of astrocytes, while ERK signaling plays a prominent role in oligodendrocyte fate specification, and SHH signaling is required for the fate determination of olfactory bulb interneurons. We provide evidence suggesting that this mechanism is conserved in both mice and humans. Finally, we propose a unifying principle of mammalian cortical gliogenesis.

Assessing candidate DLX-regulated genes in the first pharyngeal arch of chick embryos

BACKGROUND

Insights into the development and evolution of asymmetrical jaws will require an understanding of the gene regulatory networks that underpin the differential morphogenesis of the maxillary and mandibular domains of the first pharyngeal arch in a variety of gnathostomes. While a robust relationship has been demonstrated between jaw patterning and the Endothelin-Dlx gene axis, much less is known of the next level of genes in the jaw patterning hierarchy.

RESULTS

Several genes, whose expression depends on Dlx5 and/or Dlx6, have been identified in mice. Here, we examined the expression patterns of the chick orthologues of some of those genes, namely GSC, PITX1, HAND2, and GBX2, and tested their dependence on endothelin signaling to assess whether there is a conserved regulatory relationship between those genes in the chick embryo. To further validate these genes as direct DLX targets, we identified conserved non-coding sequences containing candidate DLX binding motifs and demonstrated DLX-responsiveness in vitro.

CONCLUSIONS

The evidence presented in this study combines to support the hypothesis that these four genes are direct targets of DLX transcription factors in the lower jaw-forming tissue.

Manipulated mesenchymal stem cell therapy in the treatment of Parkinson's disease

Mesenchymal stem cell (MSC) therapy has been considered a promising approach for the treatment of Parkinson's disease (PD) for several years. PD is a globally prevalent neurodegenerative disease characterized by the accumulation of Lewy bodies and the loss of dopaminergic neurons, leading to severe motor and non-motor complications in patients. As current treatments are unable to halt the progression of neuronal loss and dopamine degradation, MSC therapy has emerged as a highly promising strategy for PD treatment. This promise is due to MSCs' unique properties compared to other types of stem cells, including self-renewal, differentiation potential, immune privilege, secretion of neurotrophic factors, ability to improve damaged tissue, modulation of the immune system, and lack of ethical concerns. MSCs have been employed in numerous pre-clinical and clinical studies for PD treatment with promising results. However, certain aspects of their efficacy in treating PD may benefit from various genetic and epigenetic modifications. In this review article, we assess these approaches to improving MSCs for specialized treatment of PD.

Chromatin accessibility: biological functions, molecular mechanisms and therapeutic application

The dynamic regulation of chromatin accessibility is one of the prominent characteristics of eukaryotic genome. The inaccessible regions are mainly located in heterochromatin, which is multilevel compressed and access restricted. The remaining accessible loci are generally located in the euchromatin, which have less nucleosome occupancy and higher regulatory activity. The opening of chromatin is the most important prerequisite for DNA transcription, replication, and damage repair, which is regulated by genetic, epigenetic, environmental, and other factors, playing a vital role in multiple biological progresses. Currently, based on the susceptibility difference of occupied or free DNA to enzymatic cleavage, solubility, methylation, and transposition, there are many methods to detect chromatin accessibility both in bulk and single-cell level. Through combining with high-throughput sequencing, the genome-wide chromatin accessibility landscape of many tissues and cells types also have been constructed. The chromatin accessibility feature is distinct in different tissues and biological states. Research on the regulation network of chromatin accessibility is crucial for uncovering the secret of various biological processes. In this review, we comprehensively introduced the major functions and mechanisms of chromatin accessibility variation in different physiological and pathological processes, meanwhile, the targeted therapies based on chromatin dynamics regulation are also summarized.

Gene expression profiles of endothelium, microglia and oligodendrocytes in hippocampus of post-stroke depression rat at single cell resolution

Post-stroke depression (PSD) is a common but severe mental complication after stroke. However, the cellular and molecular understanding of PSD is still yet to be illustrated. In current study, we prepared PSD rat model (MD) via unilateral middle cerebral artery occlusion (MCAO) and chronic stress stimulation (DEPR), and isolated hippocampal tissues for single cell sequencing of 10x Genomics Chromium. First, we determined the presence of the increased cell population of endothelium and microglia and the compromised oligodendrocytes in MD compared to NC, MCAO and DEPR. The enriched functions of highly variable genes (HVGs) of endothelium and microglia suggested a reinforced blood-brain barrier in MD. Next, cell clusters of endothelium, microglia and oligodendrocytes were individually analyzed, and the subtypes with distinct functions were identified. The presence of expression profiles, intercellular communications and signaling pathways of these three cell populations of PSD displayed a similar but more aggressive appearance with DEPR compared to MCAO and NC. Taken together, this study characterized the specific gene profile of endothelium, microglia and oligodendrocytes of hippocampal PSD by single cell sequencing, emphasizing the crosstalk among them to provide theoretical basis for the in-depth mechanism research and drug therapy of PSD.

HDAC1 and HDAC2 orchestrate Wnt signaling to regulate neural progenitor transition during brain development

Tightly controlled neurogenesis is crucial for generating the precise number of neurons and establishing the intricate architecture of the cortex, with deficiencies often leading to neurodevelopmental disorders. Neuroepithelial progenitors (NPs) transit into radial glial progenitors (RGPs) to initiate neural differentiation, yet the governing mechanisms remain elusive. Here, we found that histone deacetylases 1 and 2 (HDAC1/2) mediated suppression of Wnt signaling is essential for the NP-to-RGP transition. Conditional depletion of HDAC1/2 from NPs upregulated Wnt signaling genes, impairing the transition to RGPs and resulting in rosette structures within the neocortex. Multi-omics analysis revealed that HDAC1/2 are critical for downregulating Wnt signaling, identifying Wnt9a as a key target. Overexpression of Wnt9a led to an increased population of NPs and the disruption of cortical organization. Notably, Wnt inhibitor administration partially rescued the disrupted cortical architecture. Our findings reveal the significance of tightly controlled Wnt signaling through epigenetic mechanisms in neocortical development.

Lateral/caudal ganglionic eminence makes limited contribution to cortical oligodendrocytes

The emergence of myelinating oligodendrocytes represents a pivotal developmental milestone in vertebrates, given their capacity to ensheath axons and facilitate the swift conduction of action potentials. It is widely accepted that cortical oligodendrocyte progenitor cells (OPCs) arise from medial ganglionic eminence (MGE), lateral/caudal ganglionic eminence (LGE/CGE), and cortical radial glial cells (RGCs). Here, we used two different fate mapping strategies to challenge the established notion that the LGE generates cortical OPCs. Furthermore, we used a Cre/loxP-dependent exclusion strategy to reveal that the LGE/CGE does not give rise to cortical OPCs. Additionally, we showed that specifically eliminating MGE-derived OPCs leads to a significant reduction of cortical OPCs. Together, our findings indicate that the LGE does not generate cortical OPCs, contrary to previous beliefs. These findings provide a new view of the developmental origins of cortical OPCs and a valuable foundation for future research on both normal development and oligodendrocyte-related disease.

DLX genes and proteins in mammalian forebrain development

The vertebrate Dlx gene family encode homeobox transcription factors that are related to the Drosophila Distal-less (Dll) gene and are crucial for development. Over the last ∼35 years detailed information has accrued about the redundant and unique expression and function of the six mammalian Dlx family genes. DLX proteins interact with general transcriptional regulators, and co-bind with other transcription factors to enhancer elements with highly specific activity in the developing forebrain. Integration of the genetic and biochemical data has yielded a foundation for a gene regulatory network governing the differentiation of forebrain GABAergic neurons. In this Primer, we describe the discovery of vertebrate Dlx genes and their crucial roles in embryonic development. We largely focus on the role of Dlx family genes in mammalian forebrain development revealed through studies in mice. Finally, we highlight questions that remain unanswered regarding vertebrate Dlx genes despite over 30 years of research.

Unveiling the molecular structure and role of RBBP4/7: implications for epigenetic regulation and cancer research

Retinoblastoma-binding protein (RBBP) family is a class of proteins that can interact with tumor suppressor retinoblastoma protein (pRb). RBBP4 and RBBP7 are the only pair of homologous proteins in this family, serving as scaffold proteins whose main function is to offer a platform to indirectly connect two proteins. This characteristic allows them to extensively participate in the binding of various proteins and epigenetic complexes, indirectly influencing the function of effector proteins. As a result, they are often highlighted in organism activities involving active epigenetic modifications, such as embryonic development and cancer activation. In this review, we summarize the structural characteristics of RBBP4/7, the complexes they are involved in, their roles in embryonic development and cancer, as well as potential future research directions, which we hope to inspire the field of epigenetic research in the future.

Conserved mechanisms of NuRD function in hematopoetic gene expression

The Nucleosome Remodeling and Deacetylating Complex (NuRD) is ubiquitously expressed in all metazoans. It combines nucleosome remodeling and histone deacetylating activities to generate inaccessible chromatin structures and to repress gene transcription. NuRD is involved in the generation and maintenance of a wide variety of lineage-specific gene expression programs during differentiation and in differentiated cells. A close cooperation with a large number of lineage-specific transcription factors is key to allow NuRD to function in many distinct differentiation contexts. The molecular nature of this interplay between transcription factors and NuRD is complex and not well understood. This review uses hematopoiesis as a paradigm to highlight recent advances in our understanding of how transcription factors and NuRD cooperate at the molecular level during differentiation. A comparison of vertebrate and invertebrate systems serves to identify the conserved and fundamental concepts guiding functional interactions between transcription factors and NuRD. We also discuss how the transcription factor-NuRD axis constitutes a potential therapeutic target for the treatment of hemoglobinopathies.

Nervous tract-bioinspired multi-nanoyarn model system regulating neural differentiation and its transcriptional architecture at single-cell resolution

Bioinspired by native nervous tracts, a spinal cord-mimicking model system that was composed of multiple nanofibrous yarns (NYs) ensheathed in a nanofibrous tube was constructed by an innovative electrospinning-based fabrication and integration strategy. The infilling NYs exhibited uniaxially aligned nanofibrous architecture that had a great resemblance to spatially-arranged native nervous tracts, while the outer nanofibrous tubes functioned as an artificial dura matter to provide a stable intraluminal microenvironment. The three-dimensional (3D) NYs were demonstrated to induce alignment, facilitate migration, promote neuronal differentiation, and even phenotypic maturation of seeded neural stem and progenitor cells (NSPCs), while inhibiting gliogenesis. Single-cell transcriptome analysis showed that the NSPC-loaded 3D NY model shared many similarities with native spinal cords, with a great increase in excitatory/inhibitory (EI) neuron ratio. Curcumin, as a model drug, was encapsulated into nanofibers of NYs to exert an antioxidant effect and enhanced axon regeneration. Overall, this study provides a new paradigm for the development of a next-generation in vitro neuronal model system via anatomically accurate nervous tract simulation and constructs a blueprint for the research on NSPC diversification in the biomimetic microenvironment.

Endogenous neural stem cells characterization using omics approaches: Current knowledge in health and disease

Neural stem cells (NSCs), an invaluable source of neuronal and glial progeny, have been widely interrogated in the last twenty years, mainly to understand their therapeutic potential. Most of the studies were performed with cells derived from pluripotent stem cells of either rodents or humans, and have mainly focused on their potential in regenerative medicine. High-throughput omics technologies, such as transcriptomics, epigenetics, proteomics, and metabolomics, which exploded in the past decade, represent a powerful tool to investigate the molecular mechanisms characterizing the heterogeneity of endogenous NSCs. The transition from bulk studies to single cell approaches brought significant insights by revealing complex system phenotypes, from the molecular to the organism level. Here, we will discuss the current literature that has been greatly enriched in the “omics era”, successfully exploring the nature and function of endogenous NSCs and the process of neurogenesis. Overall, the information obtained from omics studies of endogenous NSCs provides a sharper picture of NSCs function during neurodevelopment in healthy and in perturbed environments.