Project description:Periventricular nodular heterotopia is a malformation of cortical development characterized by nodules of abnormally migrated neurons.
Project description:Malformations of the human cortex represent a major cause of disability. Mouse models with mutations in known causal genes only partially recapitulate the phenotypes and are therefore not unlimitedly suited for understanding the molecular and cellular mechanisms responsible for these conditions. Here we study periventricular heterotopia (PH) by analyzing cerebral organoids derived from induced pluripotent stem cells of patients with mutations in the cadherin receptor-ligand pair DCHS1 and FAT4 or from isogenic knock-out lines. Our results show that human cerebral organoids reproduce the cortical heterotopia associated with PH. Mutations in DCHS1 and FAT4 or knock-down of their expression cause changes in the morphology of neural progenitor cells and result in defective neuronal migration dynamics only in a subset of neurons. Single-cell RNA-sequencing data reveal a subpopulation of mutant neurons with dysregulated genes involved in axon guidance, neuronal migration and patterning. We suggest that defective neural progenitor cell (NPC) morphology and an altered navigation system in a subset of neurons underlie this form of periventricular heterotopia.
Project description:Here we demonstrate the ability to model patient variants associated with two different NDDs in vivo using Breasi-CRISPR. We first model periventricular nodular heterotopia (PVNH), a neuronal migration disorder (Heinzen et al., 2018; Walters et al., 2018). We use Breasi-CRISPR to insert two patient analogous protein truncating variants in MAP1B, resulting in a significant defect in migration. We were able to validate that MAP1B fragments are being produced from these protein truncating variants, but the fragments do not act as a dominant negative. Next, we modeled a patient variant in CCND2 (encoding the protein cyclin D2) associated with megalencephaly postaxial polydactyly polymicrogyria hydrocephalus (MPPH) syndrome (Mirzaa et al., 2014). The unifying pathogenic mechanism underlying MPPH syndrome is believed to be excessive cyclin D2, a cell cycle regulator known to promote cell cycle progression. Modeling the repeated variant Thr280Ala caused an increase in the number of cells in S phase, an increase in progenitor numbers, an accumulation of cyclin D2 protein, and a tangential expansion of the cortex. We wondered if Breasi-CRISPR would be efficient enough to notice transcriptomic changes via bulk RNA sequencing of the targeted area. Indeed, we found that introduction of the MPPH syndrome variant caused an upregulation of genes and pathways important in tissue growth and a downregulation of those important in cell differentiation. Taken together we demonstrate that Breasi-CRISPR is efficient enough to model patient analogous variants, mirroring patient phenotypes and enabling investigation of NDDs.
Project description:Periventricular Heterotopia (PH) is a malformation of cerebral cortical development characterized by the presence of neurons along the wall of lateral ventricles. The most notable neurological symptoms are seizures that usually first appear when PH becomes evident during the teenage years. Heterozygous loss of function mutations within the FLNA gene in Xq28 are the most frequent cause of familial PH, while the genotype-phenotype correlation has not been well established. We generated a mouse model of PH by conditionally deleting Flna in neural progenitors along with a Flnb null mutation. In this mouse model, periventricular neurons are predominantly generated in postnatal ages. To understand the pathogenesis of PH and the mechanism of postnatal- adult neurogenesis, we assessed transcriptomic alterations resulting from Flna and Flnb double loss of function in the ventricular/subventricular zone (V-SVZ), upper cortical layers, and periventricular neurons, respectively. This dataset reveals spatially-dependent differential gene expressions between PH and their normal control counterparts at 3 months of age.
Project description:Despite the crucial importance of the centrosome in brain development and disease, its comprehensive proteome remains uncharacterized in neural cells. Here, we used spatial proteomics to elucidate protein interaction networks at the centrosome of iPSC-derived human neural stem cells (NSCs) and neurons. Centrosome-associated proteins were largely cell-type specific, with protein hubs involved in RNA-dynamics. Analysis of neurodevelopmental disease cohorts identified a significant overrepresentation of NSC centrosome proteins with variants in patients with periventricular heterotopia (PH). Expressing the PH-associated mutant splicing factor PRPF6 reproduced the periventricular misplacement in the developing mouse brain, highlighting mis-splicing of transcripts of the MAP-kinase SAD-A at centrosomal location as essential for the phenotype. Collectively, cell-type specific centrosome interactomes explain how genetic variants in ubiquitous proteins may convey brain-specific phenotypes.
Project description:In this study, we found that ablation of genes encoding ciliary transport proteins such as intraflagellar transport homolog 88 (Ift88) and kinesin family member 3a (Kif3a) in cortical radial progenitors led to periventricular heterotopia during late mouse embryogenesis. Conditional mutation of primary cilia unexpectedly caused breakdown of both the neuroepithelial lining and the blood-choroid plexus barrier. Choroidal leakage was partially caused by enlargement of the choroid plexus in the cilia mutants. We found that the choroid plexus expressed platelet-derived growth factor A (Pdgf-A) and that Pdgf-A expression was ectopically increased in cilia-mutant embryos. Cortices obtained from embryos in utero electroporated with Pdgfa mimicked periventricular heterotopic nodules of the cilia mutant.
Project description:Despite the crucial importance of the centrosome in brain development and disease, its comprehensive proteome remains uncharacterized in neural cells. Here, we used spatial proteomics to elucidate protein interaction networks at the centrosome of iPSC-derived human neural stem cells (NSCs) and neurons. Centrosome-associated proteins were largely cell type-specific, with protein hubs involved in RNA dynamics. Analysis of neurodevelopmental disease cohorts identified a significant overrepresentation of NSC centrosome proteins with variants in patients with periventricular heterotopia (PH). Expressing the PH-associated mutant splicing factor PRPF6 reproduced the periventricular misplacement in the developing mouse brain, highlighting mis-splicing of transcripts of the MAP-kinase SAD-A at centrosomal location as essential for the phenotype. Collectively, cell type-specific centrosome interactomes explain how genetic variants in ubiquitous proteins may convey brain-specific phenotypes.
Project description:Periventricular heterotopia (PH), the most common form of grey matter heterotopia, represents a cortical malformation that is often associated with developmental delay and drug-resistant seizures1,2. The detailed neurophysiological underpinnings of PH symptoms in humans remain, however, elusive. Human cerebral organoids (hCOs) derived from patients with causative mutations in FAT4 or DCHS1 exhibit key features of PH3, but neuronal activity in these 3D models has not yet been investigated. Here, using silicon probe recordings, we detected exaggerated spontaneous spike activity in FAT4 and DCHS1 hCOs, suggesting functional changes in neuronal networks. Patch-clamp recordings revealed a decreased spike threshold exclusively for DCHS1 neurons, which presumably results from an enhanced density of somatic voltage-gated sodium channels. Furthermore, single-cell morphological reconstructions and immunostainings demonstrated greater morphological complexity of neurons and synaptic alterations, rather than an imbalance of excitatory-inhibitory neuron number, as contributing to the hyperactivity observed in FAT4 and DCHS1 hCOs. The morphological phenotype was rescued by an expression of wild-type DCHS1 in DCHS1 neurons. In addition, transcriptome and proteome analyses uncovered changes in GO terms associated with neuronal morphology and synaptic function. Overall, we provide detailed new insights into cellular alterations likely contributing to the emergence of symptoms in grey matter heterotopia.
Project description:Periventricular heterotopia (PH), the most common form of grey matter heterotopia, represents a cortical malformation that is often associated with developmental delay and drug-resistant seizures1,2. The detailed neurophysiological underpinnings of PH symptoms in humans remain, however, elusive. Human cerebral organoids (hCOs) derived from patients with causative mutations in FAT4 or DCHS1 exhibit key features of PH3, but neuronal activity in these 3D models has not yet been investigated. Here, using silicon probe recordings, we detected exaggerated spontaneous spike activity in FAT4 and DCHS1 hCOs, suggesting functional changes in neuronal networks. Patch-clamp recordings revealed a decreased spike threshold exclusively for DCHS1 neurons, which presumably results from an enhanced density of somatic voltage-gated sodium channels. Furthermore, single-cell morphological reconstructions and immunostainings demonstrated greater morphological complexity of neurons and synaptic alterations, rather than an imbalance of excitatory-inhibitory neuron number, as contributing to the hyperactivity observed in FAT4 and DCHS1 hCOs. The morphological phenotype was rescued by an expression of wild-type DCHS1 in DCHS1 neurons. In addition, transcriptome and proteome analyses uncovered changes in GO terms associated with neuronal morphology and synaptic function. Overall, we provide detailed new insights into cellular alterations likely contributing to the emergence of symptoms in grey matter heterotopia.