Project description:Recent developments in molecular programming of mesodiencephalic dopaminergic (mdDA) neurons have led to the identification of many transcription factors playing a role in mdDA specification. LIM homeodomain transcription factor Lmx1a is essential for chick mdDA development, and for the efficient differentiation of ES-cells towards a dopaminergic phenotype. In this study, we aimed towards a more detailed understanding of the subtle phenotype in Lmx1a-dr/dr mice. Therefore, microarray analysis was performed, to elucidate the exact molecular programming underlying the neuronal deficits after loss of Lmx1a. Subsequent expression analysis confirmed that Nurr1 is regulated by Lmx1a, and additional downstream targets were identified, like Pou4f1, Pbx1, Pitx2, C130021l20Rik, Calb2 and Rspo2. In line with a specific, rostral-lateral loss of expression of most of these genes during development, Nurr1 and C130021l20Rik were affected in the SNc of the mature mdDA system. Interestingly, this deficit was marked by the complete loss of the Wnt/b-catenin signaling activator Rspo2 in this domain. Expression analysis in Rspo2-/- embryos revealed affected mdDA neurons, partially phenocopying the Lmx1a mutant. Together, in this study we reveal that Lmx1a is essential for a rostral-lateral subset of the mdDA neuronal field, where it might serve a critical function in modulating proliferation and differentiation of mdDA progenitors through the activation of the Wnt activator Rspo2. Microarray expression study comparing 4 samples of homozygous LMX1A dr/dr mice, midbrain E12.5 with a pooled sample of their wt/wt littermates. Two samples were analyzed in opposite dye orientation.
Project description:Recent developments in molecular programming of mesodiencephalic dopaminergic (mdDA) neurons have led to the identification of many transcription factors playing a role in mdDA specification. LIM homeodomain transcription factor Lmx1a is essential for chick mdDA development, and for the efficient differentiation of ES-cells towards a dopaminergic phenotype. In this study, we aimed towards a more detailed understanding of the subtle phenotype in Lmx1a-dr/dr mice. Therefore, microarray analysis was performed, to elucidate the exact molecular programming underlying the neuronal deficits after loss of Lmx1a. Subsequent expression analysis confirmed that Nurr1 is regulated by Lmx1a, and additional downstream targets were identified, like Pou4f1, Pbx1, Pitx2, C130021l20Rik, Calb2 and Rspo2. In line with a specific, rostral-lateral loss of expression of most of these genes during development, Nurr1 and C130021l20Rik were affected in the SNc of the mature mdDA system. Interestingly, this deficit was marked by the complete loss of the Wnt/b-catenin signaling activator Rspo2 in this domain. Expression analysis in Rspo2-/- embryos revealed affected mdDA neurons, partially phenocopying the Lmx1a mutant. Together, in this study we reveal that Lmx1a is essential for a rostral-lateral subset of the mdDA neuronal field, where it might serve a critical function in modulating proliferation and differentiation of mdDA progenitors through the activation of the Wnt activator Rspo2.
Project description:The LIM homeodomain transcription factor Lmx1a is a very potential inducer of stem cells towards dopaminergic neurons. Despite several studies on the function of this gene, the exact in vivo role of Lmx1a in mesodiencephalic dopamine (mdDA) neuronal specification is still not understood. To analyze the genes functioning downstream of Lmx1a, we performed expression microarray analysis of LMX1A overexpressing MN9D dopaminergic cells. Several interesting regulated genes were identified, based on their regulation in other, previously generated expression arrays, and their expression pattern in the developing mdDA neuronal field. Post analysis through in vivo expression analysis in Lmx1a mouse mutant (drJ/drJ) embryos demonstrated a clear decrease in expression of the genes Grb10 and Rgs4, in and adjacent to the rostral and dorsal mdDA neuronal field and within the Lmx1a expression domain. Interestingly, the DA marker Vmat2 was significantly up-regulated as a consequence of increased LMX1A dose, and subsequent analysis on Lmx1a mutant E14.5 and adult tissue revealed a significant decrease in Vmat2 expression in mdDA neurons. Taken together, microarray analysis of an LMX1A overexpression cell system resulted in the identification of novel downstream targets of Lmx1A in mdDA neurons: Grb10, Rgs4 and Vmat2.
Project description:The LIM homeodomain transcription factor Lmx1a is a very potential inducer of stem cells towards dopaminergic neurons. Despite several studies on the function of this gene, the exact in vivo role of Lmx1a in mesodiencephalic dopamine (mdDA) neuronal specification is still not understood. To analyze the genes functioning downstream of Lmx1a, we performed expression microarray analysis of LMX1A overexpressing MN9D dopaminergic cells. Several interesting regulated genes were identified, based on their regulation in other, previously generated expression arrays, and their expression pattern in the developing mdDA neuronal field. Post analysis through in vivo expression analysis in Lmx1a mouse mutant (drJ/drJ) embryos demonstrated a clear decrease in expression of the genes Grb10 and Rgs4, in and adjacent to the rostral and dorsal mdDA neuronal field and within the Lmx1a expression domain. Interestingly, the DA marker Vmat2 was significantly up-regulated as a consequence of increased LMX1A dose, and subsequent analysis on Lmx1a mutant E14.5 and adult tissue revealed a significant decrease in Vmat2 expression in mdDA neurons. Taken together, microarray analysis of an LMX1A overexpression cell system resulted in the identification of novel downstream targets of Lmx1A in mdDA neurons: Grb10, Rgs4 and Vmat2. RNA was isolated from MN9D cells. Each experimental sample consisted of a RNA pool derived from 3 separate 10-cm dishes containing Lmx1a overexpressing MN9D cells (transfected with pcDNA3.1(-)-Lmx1a). microarray analysis was performed in triplicate, each experimental sample was hybridized to the same reference pool of RNA derived from 9 10-cm dishes containing control MN9D cells (transfected with empty pcDNA3.1(-)). On each of three microarray samples, dye swap was performed to correct for dye effects.
Project description:The development of the mesodiencephalic dopaminergic (mdDA) neurons strongly depends on the WNT1/b-catenin signaling pathway. These neurons include the Substantia nigra pars compacta (SNc) subset that preferentially degenerates in Parkinson’s Disease (PD), and the ventral tegmental area (VTA) subpopulation implicated in a variety of neuropsychiatric disorders. The identity of the cells responding to this signaling pathway in the developing mammalian ventral midbrain (VM) and the precise mechanism of WNT/b-catenin action in these cells, however, are still unknown. Moreover, this signaling pathway has to be accurately balanced during mdDA neuron development: whereas low levels or absence of WNT1/b-catenin signaling abolish their correct specification, constitutive activation of this signaling pathway prevents their proper differentiation in the mouse. We show that the WNT/b-catenin-responsive cells constitute only a fraction of all mdDA progenitors, precursors and neurons in the murine VM. These WNT/b-catenin-responsive cells are mostly located in the Wnt1+, Rspo2+ and Lef1+ lateral floor plate of the medial and caudal midbrain, giving preferentially rise to caudomedial (VTA) mdDA neurons. Strong WNT/b-catenin signaling mediated by RSPO2, a WNT/b-catenin agonist, and LEF1, a nuclear effector of this pathway, inhibits the differentiation of WNT/b-catenin-responsive mdDA progenitors into mature mdDA neurons by repressing the murine Pitx3 gene via conserved LEF1/TCF binding sites in its promoter. Our data indicate that an attenuation of WNT/b-catenin signaling in mdDA progenitors is essential for their correct differentiation into specific mdDA neuron subsets, thus providing a new means for stem cell-based regenerative therapies of PD and in vitro models of neuropsychiatric diseases.
Project description:Despite the progress in safety and efficacy of cell therapy with pluripotent stem cells (PSCs), the presence of residual undifferentiated stem cells or proliferating neural progenitor cells (NPCs) with rostral identity has remained a major challenge. Here we reported the generation of an LMX1A knock-in GFP reporter human embryonic stem cell (hESC) line that marks the early dopaminergic progenitors during neural differentiation. Purified GFP positive cells in vitro exhibited expression of mRNA and proteins that characterized and matched the midbrain dopaminergic identity. Further proteomic analysis of enriched LMX1A+ cells identified several membrane associated proteins including CNTN2, enabling prospective isolation of LMX1A+ progenitor cells. Transplantation of hPSC-derived purified CNTN2+ progenitors enhanced dopamine release from transplanted cells in the host brain and alleviated Parkinson’s disease symptoms in animal models. Our study establishes an efficient approach for purification of large numbers of hPSC-derived dopaminergic progenitors for therapeutic applications.
Project description:WNT1/beta-catenin signaling plays a crucial role in the generation of mesodiencephalic dopaminergic (mdDA) neurons including the Substantia nigra pars compacta (SNc) subpopulation, whose degeneration is a hallmark of Parkinson’s Disease (PD). However, the precise functions of WNT/beta-catenin signaling in this context remain unknown. Using mutant mice, primary ventral midbrain (VM) cells and pluripotent stem cells (mouse embryonic stem cells and induced pluripotent stem cells), we show that Dickkopf 3 (DKK3), a secreted glycoprotein that modulates WNT/beta-catenin signaling, is specifically required for the correct differentiation of a rostrolateral mdDA precursor subset into SNc DA neurons. Dkk3 transcription in the murine VM coincides with the onset of mdDA neurogenesis and is required for the maintenance of LMX1A and consequently PITX3 expression in rostrolateral mdDA precursors, without affecting the proliferation or specification of their progenitors. Treatment of primary VM cells or differentiating pluripotent stem cells with recombinant WNT1 and/or DKK3 proteins consistently increases the proportion of mdDA cells with SNc DA neuron identity and promotes their survival in vitro. The SNc DA pro-differentiation and pro-survival properties of DKK3, together with its known anti-tumorigenic effect, therefore make it an ideal candidate for the improvement of regenerative and neuroprotective strategies in the treatment of PD. We performed gene expression microarray analysis on iPSC-derived and FACS-sorted GFP-positive Pitx3GFP/+ mdDA neurons, differentiated in the presence or absence of recombinant human WNT1 and recombinant human DKK3. In addition, we analysed primary and FACS-sorted GFP-positive Pitx3+/GFP mdDA neurons isolated from the E13.5 and E14.5 ventral midbrain of Pitx3+/GFP embryos
Project description:Intellectual disability (ID) affects ~2% of the population and ID-associated genes are enriched for epigenetic factors, including those encoding the largest family of histone lysine acetyltransferases (KAT5-KAT8). Among them is KAT6A, whose mutations cause KAT6A Syndrome, with ID as a common clinical feature. However, the underlying molecular mechanism remains unknown. Here, we find that KAT6A deficiency impairs synaptic structure and plasticity in hippocampal CA3, but not in CA1 region, resulting in memory deficits in mice. We further identify a CA3-enriched gene Rspo2, encoding Wnt activator R-spondin 2, as a key transcriptional target of KAT6A. Importantly, deletion of Rspo2 in excitatory neurons impairs memory formation, and restoring RSPO2 expression in CA3 rescues the deficits in Wnt signaling and learning-associated behaviors in Kat6a mutant mice. Collectively, our results demonstrate that KAT6A-RSPO2-Wnt signaling plays a critical role in regulating hippocampal CA3 synaptic plasticity and cognitive function, providing potential therapeutic targets for KAT6A Syndrome and related neurodevelopmental diseases.
Project description:Intellectual disability (ID) affects ~2% of the population and ID-associated genes are enriched for epigenetic factors, including those encoding the largest family of histone lysine acetyltransferases (KAT5-KAT8). Among them is KAT6A, whose mutations cause KAT6A Syndrome, with ID as a common clinical feature. However, the underlying molecular mechanism remains unknown. Here, we find that KAT6A deficiency impairs synaptic structure and plasticity in hippocampal CA3, but not in CA1 region, resulting in memory deficits in mice. We further identify a CA3-enriched gene Rspo2, encoding Wnt activator R-spondin 2, as a key transcriptional target of KAT6A. Importantly, deletion of Rspo2 in excitatory neurons impairs memory formation, and restoring RSPO2 expression in CA3 rescues the deficits in Wnt signaling and learning-associated behaviors in Kat6a mutant mice. Collectively, our results demonstrate that KAT6A-RSPO2-Wnt signaling plays a critical role in regulating hippocampal CA3 synaptic plasticity and cognitive function, providing potential therapeutic targets for KAT6A Syndrome and related neurodevelopmental diseases.
Project description:WNT1/beta-catenin signaling plays a crucial role in the generation of mesodiencephalic dopaminergic (mdDA) neurons including the Substantia nigra pars compacta (SNc) subpopulation, whose degeneration is a hallmark of Parkinson’s Disease (PD). However, the precise functions of WNT/beta-catenin signaling in this context remain unknown. Using mutant mice, primary ventral midbrain (VM) cells and pluripotent stem cells (mouse embryonic stem cells and induced pluripotent stem cells), we show that Dickkopf 3 (DKK3), a secreted glycoprotein that modulates WNT/beta-catenin signaling, is specifically required for the correct differentiation of a rostrolateral mdDA precursor subset into SNc DA neurons. Dkk3 transcription in the murine VM coincides with the onset of mdDA neurogenesis and is required for the maintenance of LMX1A and consequently PITX3 expression in rostrolateral mdDA precursors, without affecting the proliferation or specification of their progenitors. Treatment of primary VM cells or differentiating pluripotent stem cells with recombinant WNT1 and/or DKK3 proteins consistently increases the proportion of mdDA cells with SNc DA neuron identity and promotes their survival in vitro. The SNc DA pro-differentiation and pro-survival properties of DKK3, together with its known anti-tumorigenic effect, therefore make it an ideal candidate for the improvement of regenerative and neuroprotective strategies in the treatment of PD.