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Project description:Current ventral midbrain dopaminergic progenitor differentiation protocols utilize small molecule inhibitors targeting Glycogen synthase kinase-3 (GSK3) to activate Wnt signaling, a step required for the anterior-posterior patterning of the nervous system and acquisition of the midbrain fate. However, GSK3a and GSK3β are pleiotropic kinases involved in multiple signaling pathways and their inhibition is a known trigger of neurogenesis. We predicted that direct activation of specific Wnt receptors naturally involved during neural patterning would allow for a more precise spatiotemporal control of Wnt/β-catenin signaling and mimic endogenous cell-cell communication mechanisms to improve hPSC differentiation. Here, we characterized the expression of FZD receptors at the surface of neural progenitor cells with different regional identity. Our data shows that FZD5 expression is uniquely upregulated in anterior neural progenitors and is rapidly downregulated as cells adopt a posterior fate. This spatial regulation of Frizzled cell surface expression constitutes a novel regulatory mechanism adjusting the levels of β-catenin signaling along the anterior-posterior axis and possibly contribute to midbrain-hindbrain boundary formation. Using a tetravalent antibody that selectively triggers FZD5 and LRP6 clustering to activate Wnt/β-catenin signaling, we show that the resulting midbrain-patterned neural progenitors exhibit a gene expression program more closely aligned with the anatomical origin of dopaminergic neurons and could hence represent a more efficient source for cell transplant therapies.
2024-02-21 | GSE241041 | GEO
Project description:Current ventral midbrain dopaminergic progenitor differentiation protocols utilize small molecule inhibitors targeting Glycogen synthase kinase-3 (GSK3) to activate Wnt signaling, a step required for the anterior-posterior patterning of the nervous system and acquisition of the midbrain fate. However, GSK3a and GSK3β are pleiotropic kinases involved in multiple signaling pathways and their inhibition is a known trigger of neurogenesis. We predicted that direct activation of specific Wnt receptors naturally involved during neural patterning would allow for a more precise spatiotemporal control of Wnt/β-catenin signaling and mimic endogenous cell-cell communication mechanisms to improve hPSC differentiation. Here, we characterized the expression of FZD receptors at the surface of neural progenitor cells with different regional identity. Our data shows that FZD5 expression is uniquely upregulated in anterior neural progenitors and is rapidly downregulated as cells adopt a posterior fate. This spatial regulation of Frizzled cell surface expression constitutes a novel regulatory mechanism adjusting the levels of β-catenin signaling along the anterior-posterior axis and possibly contribute to midbrain-hindbrain boundary formation. Using a tetravalent antibody that selectively triggers FZD5 and LRP6 clustering to activate Wnt/β-catenin signaling, we show that the resulting midbrain-patterned neural progenitors exhibit a gene expression program more closely aligned with the anatomical origin of dopaminergic neurons and could hence represent a more efficient source for cell transplant therapies.
2024-02-21 | GSE241042 | GEO
Project description:Human embryonic stem (hES) cells are defined by their extensive self-renewal capacity and their potential to differentiate into any cell type of the human body. The challenge in using hES cells for developmental biology and regenerative medicine has been to direct the wide differentiation potential toward the derivation of a specific cell fate. Within the nervous system, hES cells have been shown to differentiate in vitro into neural progenitor cells, neurons, and astrocytes. However, to our knowledge, the selective derivation of any given neuron subtype has not yet been demonstrated. Here, we describe conditions to direct hES cells into neurons of midbrain dopaminergic identity. Neuroectodermal differentiation was triggered on stromal feeder cells followed by regional specification by means of the sequential application of defined patterning molecules that direct in vivo midbrain development. Progression toward a midbrain dopamine (DA) neuron fate was monitored by the sequential expression of key transcription factors, including Pax2, Pax5, and engrailed-1 (En1), measurements of DA release, the presence of tetrodotoxin-sensitive action potentials, and the electron-microscopic visualization of tyrosinehydroxylase-positive synaptic terminals. High-yield DA neuron derivation was confirmed from three independent hES and two monkey embryonic stem cell lines. The availability of unlimited numbers of midbrain DA neurons is a first step toward exploring the potential of hES cells in preclinical models of Parkinson's disease. This experimental system also provides a powerful tool to probe the molecular mechanisms that control the development and function of human midbrain DA neurons.
| S-EPMC515094 | biostudies-literature
Project description:Midbrain dopamine (MbDA) neurons are partitioned into medial and lateral cohorts that control complex functions. However, the genetic underpinnings of MbDA neuron heterogeneity are unclear. While it is known that Wnt1-expressing progenitors contribute to MbDA neurons, the role of Wnt1 in MbDA neuron development in vivo is unresolved. We show that mice with a spontaneous point mutation in Wnt1 have a unique phenotype characterized by the loss of medial MbDA neurons concomitant with a severe depletion of Wnt1-expressing progenitors and diminished LMX1a-expressing progenitors. Wnt1 mutant embryos also have alterations in a hierarchical gene regulatory loop suggesting multiple gene involvement in the Wnt1 mutant MbDA neuron phenotype. To investigate this possibility, we conditionally deleted Gbx2, Fgf8, and En1/2 after their early role in patterning and asked whether these genetic manipulations phenocopied the depletion of MbDA neurons in Wnt1 mutants. The conditional deletion of Gbx2 did not result in re-positioning or distribution of MbDA neurons. The temporal deletion of Fgf8 did not result in the loss of either LMX1a-expressing progenitors nor the initial population of differentiated MbDA neurons, but did result in a complete loss of MbDA neurons at later stages. The temporal deletion and species specific manipulation of En1/2 demonstrated a continued and species specific role of Engrailed genes in MbDA neuron development. Notably, our conditional deletion experiments revealed phenotypes dissimilar to Wnt1 mutants indicating the unique role of Wnt1 in MbDA neuron development. By placing Wnt1, Fgf8, and En1/2 in the context of their temporal requirement for MbDA neuron development, we further deciphered the developmental program underpinning MbDA neuron progenitors.
| S-EPMC3502751 | biostudies-literature
Project description:Wnt1-expressing progenitors generate midbrain dopamine (MbDA) and cerebellum (Cb) neurons in distinct temporal windows and from spatially discrete progenitor domains. It has been shown that Wnt1 and Lmx1a participate in a cross-regulatory loop that is utilized during MbDA neuron development. However, Wnt1 expression dynamically changes over time and precedes that of Lmx1a. The spatial and temporal requirements of Wnt1 in development and specifically its requirement for MbDA neurons remain to be determined. To address these issues, we generated a conditional Wnt1 allele and temporally deleted Wnt1 coupled with genetic lineage analysis. Using this approach, we show that patterning of the midbrain (Mb) and Cb by Wnt1 occurs between the one-somite and the six- to eight-somite stages and is solely dependent on Wnt1 function in the Mb, but not in the Cb. Interestingly, an En1-derived domain persists after the early deletion of Wnt1 and mutant cells express OTX2. However, the En1-derived Wnt1-mutant domain does not contain LMX1a-expressing progenitors, and MbDA neurons are depleted. Thus, we demonstrate an early requirement of Wnt1 for all MbDA neurons. Subsequently, we deleted Wnt1 in the ventral Mb and show a continued late requirement for Wnt1 in MbDA neuron development, but not in LMX1a-expressing progenitors. Specifically, Wnt1 deletion disrupts the birthdating of MbDA neurons and causes a depletion of MbDA neurons positioned medially and a concomitant expansion of MbDA neurons positioned laterally during embryogenesis. Collectively, our analyses resolve the spatial and temporal function of Wnt1 in Mb and Cb patterning and in MbDA neuron development in vivo.
| S-EPMC3585666 | biostudies-literature
Project description:Reductions in the GABAergic neurotransmitter system exist across multiple brain regions in schizophrenia and encompass both pre- and postsynaptic components. While reduced midbrain GABAergic inhibitory neurotransmission may contribute to the hyperdopaminergia thought to underpin psychosis in schizophrenia, molecular changes consistent with this have not been reported. We hypothesised that reduced GABA-related molecular markers would be found in the midbrain of people with schizophrenia and that these would correlate with dopaminergic molecular changes. We hypothesised that downregulation of inhibitory neuron markers would be exacerbated in schizophrenia cases with high levels of neuroinflammation. Eight GABAergic-related transcripts were measured with quantitative PCR, and glutamate decarboxylase (GAD) 65/67 and GABAA alpha 3 (α3) (GABRA3) protein were measured with immunoblotting, in post-mortem midbrain (28/28 and 28/26 control/schizophrenia cases for mRNA and protein, respectively), and analysed by both diagnosis and inflammatory subgroups (as previously defined by higher levels of four pro-inflammatory cytokine transcripts). We found reductions (21 - 44%) in mRNA encoding both presynaptic and postsynaptic proteins, vesicular GABA transporter (VGAT), GAD1, and parvalbumin (PV) mRNAs and four alpha subunits (α1, α2, α3, α5) of the GABAA receptor in people with schizophrenia compared to controls (p < 0.05). Gene expression of somatostatin (SST) was unchanged (p = 0.485). We confirmed the reduction in GAD at the protein level (34%, p < 0.05). When stratifying by inflammation, only GABRA3 mRNA exhibited more pronounced changes in high compared to low inflammatory subgroups in schizophrenia. GABRA3 protein was expressed by 98% of tyrosine hydroxylase-positive neurons and was 23% lower in schizophrenia, though this did not reach statistical significance (p > 0.05). Expression of transcripts for GABAA receptor alpha subunits 2 and 3 (GABRA2, GABRA3) were positively correlated with tyrosine hydroxylase (TH) and dopamine transporter (DAT) transcripts in schizophrenia cases (GABRA2; r > 0.630, GABRA3; r > 0.762, all p < 0.001) but not controls (GABRA2; r < - 0.200, GABRA3; r < 0.310, all p > 0.05). Taken together, our results support a profound disruption to inhibitory neurotransmission in the substantia nigra regardless of inflammatory status, which provides a potential mechanism for disinhibition of nigrostriatal dopamine neurotransmission.
| S-EPMC8235806 | biostudies-literature
Project description:Parkinson's disease is characterized by the loss of dopamine (DA) neurons in the substantia nigra pars compacta (SNc). DA neurons in the ventral tegmental area are more resistant to this degeneration than those in the SNc, though the mechanisms for selective resistance or vulnerability remain poorly understood. A key to elucidating these processes may lie within the subset of DA neurons that corelease glutamate and express the vesicular glutamate transporter VGLUT2. Here, we addressed the potential relationship between VGLUT expression and DA neuronal vulnerability by overexpressing VGLUT in DA neurons of flies and mice. In Drosophila, VGLUT overexpression led to loss of select DA neuron populations. Similarly, expression of VGLUT2 specifically in murine SNc DA neurons led to neuronal loss and Parkinsonian behaviors. Other neuronal cell types showed no such sensitivity, suggesting that DA neurons are distinctively vulnerable to VGLUT2 expression. Additionally, most DA neurons expressed VGLUT2 during development, and coexpression of VGLUT2 with DA markers increased following injury in the adult. Finally, conditional deletion of VGLUT2 made DA neurons more susceptible to Parkinsonian neurotoxins. These data suggest that the balance of VGLUT2 expression is a crucial determinant of DA neuron survival. Ultimately, manipulation of this VGLUT2-dependent process may represent an avenue for therapeutic development.
| S-EPMC5785252 | biostudies-literature
Project description:Midbrain dopamine (mDA) neurons constitute a heterogenous group of cells that have been intensely studied, not least because their degeneration causes major symptoms in Parkinson's disease. Understanding the diversity of mDA neurons - previously well characterized anatomically - requires a systematic molecular classification at the genome-wide gene expression level. Here, we use single cell RNA sequencing of isolated mouse neurons expressing the transcription factor Pitx3, a marker for mDA neurons. Analyses include cells isolated during development up until adulthood and the results are validated by histological characterization of newly identified markers. This identifies seven neuron subgroups divided in two major branches of developing Pitx3-expressing neurons. Five of them express dopaminergic markers, while two express glutamatergic and GABAergic markers, respectively. Analysis also indicate evolutionary conservation of diversity in humans. This comprehensive molecular characterization will provide a valuable resource for elucidating mDA neuron subgroup development and function in the mammalian brain.
| S-EPMC6362095 | biostudies-literature
Project description:Human pluripotent stem cells show considerable promise for applications in regenerative medicine, including the development of cell replacement paradigms for the treatment of Parkinson's disease. Protocols have been developed to generate authentic midbrain dopamine (mDA) neurons capable of reversing dopamine-related deficits in animal models of Parkinson's disease. However, the generation of mDA neurons at clinical scale suitable for human application remains an important challenge. Here, we present an mDA neuron derivation protocol based on a two-step WNT signaling activation strategy that improves expression of midbrain markers, such as Engrailed-1 (EN1), while minimizing expression of contaminating posterior (hindbrain) and anterior (diencephalic) lineage markers. The resulting neurons exhibit molecular, biochemical, and electrophysiological properties of mDA neurons. Cryopreserved mDA neuron precursors can be successfully transplanted into 6-hydroxydopamine (6OHDA) lesioned rats to induce recovery of amphetamine-induced rotation behavior. The protocol presented here is the basis for clinical-grade mDA neuron production and preclinical safety and efficacy studies.
| S-EPMC8006469 | biostudies-literature
Project description:Ventral tegmental area (VTA) dopamine (DA) neurons have been implicated in reward, aversion, salience, cognition, and several neuropsychiatric disorders. Optogenetic approaches involving transgenic Cre-driver mouse lines provide powerful tools for dissecting DA-specific functions. However, the emerging complexity of VTA circuits requires Cre-driver mouse lines that restrict transgene expression to a precisely defined cell population. Because of recent work reporting that VTA DA neurons projecting to the lateral habenula release GABA, but not DA, we performed an extensive anatomical, molecular, and functional characterization of prominent DA transgenic mouse driver lines. We find that transgenes under control of the tyrosine hydroxylase, but not the dopamine transporter, promoter exhibit dramatic non-DA cell-specific expression patterns within and around VTA nuclei. Our results demonstrate how Cre expression in unintentionally targeted cells in transgenic mouse lines can confound the interpretation of supposedly cell-type-specific experiments. This Matters Arising paper is in response to Stamatakis et al. (2013), published in Neuron. See also the Matters Arising Response paper by Stuber et al. (2015), published concurrently with this Matters Arising in Neuron.
| S-EPMC5037114 | biostudies-literature