Project description:One neural stem cell can produce multiple transiently amplifying, intermediate neural progenitors (INP), which collectively yield diverse neuronal types. It is unclear if and how serially derived INPs contribute to neuron fate diversification. Drosophila type II neuroblasts, like mammalian neural stem cells, deposit neurons and also glia through INPs. The consecutively born INPs in a given lineage produce morphologically distinct progeny, presumably due to their inheritance of different temporal factors from the INP-producing progenitor. To uncover the underlying temporal fating mechanisms, we profiled type II neuroblasts' transcriptome across time. Our results reveal opposing temporal gradients of Imp and Syp RNA-binding proteins (descending and ascending, respectively). Maintaining high Imp throughout serial INP production expands the number of neurons/glia with early temporal fate at the expense of cells with late fate. Conversely, precocious upregulation of Syp reduces the number of cells with early fate. Further, we reveal that the transcription factor, Seven-up initiates progression of the Imp/Syp gradients. Interestingly, neuroblasts apparently locked in their beginning Imp/Syp levels can still yield progeny with a small range of early fates. We propose that the Seven-up-initiated Imp/Syp gradients create coarse temporal windows within type II neuroblasts to pattern INPs, which subsequently undergo fine-tuned subtemporal patterning.
Project description:Correct neural progenitor fate determination requires the coordination of extrinsic fate determinant signals with intrinsic responses. Post-translational modifications dynamically alter protein function and so are ideally situated to regulate development. Here we show that the deubiquitylaying enzyme, Usp9x modulates both intrinsic and extrinsic regulators of mouse neural progenitors. Nestin-cre mediated deletion of Usp9x from neural progenitors results in a transient disruption of cell adhesion and apical-basal polarity as well as the premature differentiation of intermediate neural progenitors. Ablation of Usp9x also significantly increased β-catenin protein levels, especially S33/S37/T41 phospho-β-catenin, and Wnt signalling. Usp9x was found to be part of the β-catenin destruction complex and loss of Usp9x affects destruction complex composition. Notch signalling was also increased in Usp9x ablated neural progenitors, coinciding with decreased Itch and Numb, and increased Notch intracellular domain protein levels. Usp9x co-localized and immunopreciptiated with Numb from neural progenitors suggesting it is required for Numb stabilisation. These data suggest Usp9x plays a role in coordinating intrinsic responses to extrinsic signals during neural development.
Project description:Temporal patterning of neural progenitors is an evolutionarily conserved strategy for generating neuronal diversity. Type II neural stem cells in the Drosophilacentral brain produce transit-amplifying intermediate neural progenitors (INPs) that exhibit temporal patterning. However, the known temporal factors cannotaccount for the neuronal diversity in the adult brain. To search for new temporal factors, we developed NanoDam, which enablesrapid genome-wide profiling of endogenously-tagged proteins in vivowith a singlegenetic cross.Mapping the targets of known temporal transcription factorswith NanoDamidentified Homeobrain and Scarecrow (ARX and NKX2.1 orthologues) as novel temporal factors. We show that Homeobrainand Scarecrow define middle-aged and late INP temporal windows and play a role in cellular longevity. Strikingly, Homeobrain and Scarecrow have conserved functions as temporal factors in the developing visual system.NanoDam enables rapid cell type-specific genome-wideprofiling with temporal resolution and can be easily adapted for use in higher organisms.
Project description:The cortical area map is initially patterned by transcription factor (TF) gradients in the neocortical primordium, which define a protomap in the embryonic ventricular zone (VZ). However, mechanisms that propagate regional identity from VZ progenitors to cortical plate (CP) neurons are unknown. Here we show that the VZ, subventricular zone (SVZ), and CP contain distinct molecular maps of regional identity, reflecting different gene expression gradients in radial glia progenitors, intermediate progenitors, and projection neurons, respectively. The intermediate map in SVZ is modulated by Eomes (also known as Tbr2), a T-box TF. Eomes inactivation caused rostrocaudal shifts in SVZ and CP gene expression, with loss of corticospinal axons and gain of corticotectal projections. These findings suggest that cortical areas and connections are shaped by sequential maps of regional identity, propagated by the Pax6 ? Eomes ? Tbr1 TF cascade. In humans, PAX6, EOMES, and TBR1 have been linked to intellectual disability and autism. To determine the role of Eomes in the propagation of the protomap to cortical plate neurons, used microarray analysis of E14.5 cortex from five wild type and three Eomes knockout mice.
Project description:The cortical area map is initially patterned by transcription factor (TF) gradients in the neocortical primordium, which define a protomap in the embryonic ventricular zone (VZ). However, mechanisms that propagate regional identity from VZ progenitors to cortical plate (CP) neurons are unknown. Here we show that the VZ, subventricular zone (SVZ), and CP contain distinct molecular maps of regional identity, reflecting different gene expression gradients in radial glia progenitors, intermediate progenitors, and projection neurons, respectively. The intermediate map in SVZ is modulated by Eomes (also known as Tbr2), a T-box TF. Eomes inactivation caused rostrocaudal shifts in SVZ and CP gene expression, with loss of corticospinal axons and gain of corticotectal projections. These findings suggest that cortical areas and connections are shaped by sequential maps of regional identity, propagated by the Pax6 → Eomes → Tbr1 TF cascade. In humans, PAX6, EOMES, and TBR1 have been linked to intellectual disability and autism.
Project description:Generating diverse neurons involves spatially distinct neural stem cells that show age dependent developmental fates. Drosophila neuroblasts produce long, diverse yet stereotyped series of distinct neurons, called lineages. We searched for novel temporal factors that could pattern such extended lineages by RNA-sequencing of specific neuroblasts at various developmental times. We found that two RNA-binding proteins, Imp and Syp, display opposing high-to-low and low-to-high temporal gradients with distinct dynamics in specific lineages. Manipulating Imp/Syp levels in mushroom body neuroblasts revealed opposing roles in the specification of early and late temporal fates, primarily via regulation of Chinmo translation. This study implicates the opposing Imp/Syp gradients as temporal morphogens that encode stem cell age and govern birth time-dependent offspring cell fate through post-transcriptional regulation of temporal dentity genes.
Project description:During development of the human cerebral cortex, multipotent neural progenitors generate excitatory neurons and glial cells. Investigations of the transcriptome and epigenome have revealed important gene regulatory networks underlying this crucial developmental event. However, the post-transcriptional control of gene expression and protein abundance during human corticogenesis remains poorly understood. We addressed this issue by using a dual reporter cell line to isolate neural progenitors and neurons from the telencephalic brain organoid tissue and performed cell type and developmental stage-specific transcriptome and proteome analysis. Integrating the two datasets revealed temporal modules of gene expression during human corticogenesis, both at RNA and protein level. Our multiomics approach reveals novel posttranscriptional regulatory mechanisms crucial for fidelity of cortical development.
Project description:Human embryonic stem cells with a GFP reporter knock-in into the NKX2.1 locus were differentiated and purified by FACS sorting for global gene expression analysis. Directed differentiation from human pluripotent stem cells (hPSCs) has seen significant progress in recent years. Most differentiated populations, however, exhibit immature properties of an early embryonic stage, raising concerns about their ability to model and treat disease. Here, we report the directed differentiation of hPSCs into medial ganglionic eminence (MGE)-like progenitors and their maturation into forebrain type interneurons. We find that early stage progenitors progress via a radial glial-like stem cell enriched in the human fetal brain. Both in vitro and post-transplantation into the rodent cortex, the MGE-like cells develop into GABAergic interneuron subtypes with mature physiological properties along a prolonged intrinsic timeline of up to seven months, mimicking endogenous human neural development. MGE-derived cortical interneuron deficiencies are implicated in a broad range of neurodevelopmental and degenerative disorders, highlighting the importance of these results for modeling human neural development and disease.
Project description:Human embryonic stem cells with a GFP reporter knock-in into the NKX2.1 locus were differentiated and purified by FACS sorting for global gene expression analysis. Directed differentiation from human pluripotent stem cells (hPSCs) has seen significant progress in recent years. Most differentiated populations, however, exhibit immature properties of an early embryonic stage, raising concerns about their ability to model and treat disease. Here, we report the directed differentiation of hPSCs into medial ganglionic eminence (MGE)-like progenitors and their maturation into forebrain type interneurons. We find that early stage progenitors progress via a radial glial-like stem cell enriched in the human fetal brain. Both in vitro and post-transplantation into the rodent cortex, the MGE-like cells develop into GABAergic interneuron subtypes with mature physiological properties along a prolonged intrinsic timeline of up to seven months, mimicking endogenous human neural development. MGE-derived cortical interneuron deficiencies are implicated in a broad range of neurodevelopmental and degenerative disorders, highlighting the importance of these results for modeling human neural development and disease. Human embryonic stem cells with a GFP reporter knock-in into the NKX2.1 locus were differentiated for 20, 35, and 55 days in vitro and GFP+ cells were purified by FACS sorting. Total RNA was prepared from each timepoint and compared to undifferentiated human embryonic stem cells. hESC = one sample and three technical replicates. D20 = three independent samples. D35 = one sample and two technical replicates. D55 = one sample and one technical replicate.
Project description:Neuronal restricted progenitors (NRPs) represent a type of transitional intermediate cells that lie between multipotent neural progenitors (NPs) and terminal differentiated neurons during neurogenesis. These NRPs have the ability to self-renew and differentiate into neurons, but not into glial cells, which is considered as an advantage for cellular therapy of human neurodegenerative diseases. However, difficulty in the extraction of highly purified NPRs from normal nervous tissue prevents further studies and applications. In this study, we reported conversion of human fetal dermal fibroblasts into human induced neuronal restricted progenitors (hiNRPs) in seven days by using just three defined factors: Sox2, c-Myc, and either Brn2 or Brn4. The hiNRPs exhibited distinct neuronal characteristics, including cell morphology, multiple neuronal markers expression, self-renewal capacity, and genome-wide transcriptional profile. Moreover, hiNRPs were able to differentiate into various terminal neurons with functional membrane properties, but not glial cells. Direct generation of hiNRPs from somatic cells will provide a new source of cells for cellular replacement therapy of human neurodegenerative diseases. This is a general expression microarray design (NimbleGen platform). It includes 5 samples.