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:Analysis of Beat AML sequencing data revealed a recurrent frameshift variant (R939Pfs*Ter36) in Zinc Finger 687 (ZNF687) that was observed in ~1% of patients and has not been previously described. ZNF687 encodes a transcription factor containing DNA binding C2H2 zinc finger and has been studied in select other malignancies, including Paget’s disease of bone that is associated with giant cell tumor (PDB/GCT) and hepatocellular carcinoma. It is part of a network with ZMYND8 and two additional zinc finger proteins, ZNF592 and ZNF532, that associate with H3K4 demethylation machinery and regulates gene transcription. The R939Pfs*Ter36 frameshift induced overexpression of ZNF687 compared with wild-type, and the overexpressed protein was mislocalized to the cytoplasm. We further performed RNA sequencing on HEK293 cells expressing the frameshift variant, wild-type, or a previously identified variant (P937R) that has been reported as a germline ZNF687 variant characterized to predispose to PDB/GCT. We observed the R939Pfs*Ter36 frameshift to induce activation of oxidative phosphorylation, inactivation of histone methylation machinery, and significant downregulation of lysine methyltransferase 2D (KMT2D) compared with wild-type and P937R. Overall, these findings suggest that ZNF687 R939Pfs*Ter36 plays an important role in AML pathogenesis, which could aid in diagnostic precision, and may impact therapeutic responses.
Project description:The Integrator Complex (IC) is responsible for the 3'-end processing of the U1/U2 major spliceosome snRNAs. Maturation of these snRNAs is essential for the proper function of the major spliceosome. Also, there is accumulating evidence that the IC is necessary for normal vertebrate development, however no association with human disease has been reported yet. Three siblings presented with severe intellectual disability, cerebellar hypoplasia and periventricular nodular heterotopia (PNH) of unknown cause. Using whole genome sequencing (Complete Genomics), and filtering for recessive inheritance, we discovered co-segregating compound heterozygous mutations in Integrator Complex Subunit 8 (INTS8) in the three sibs. QRT-PCR showed 2-fold decreased INTS8 RNA levels and in patients’ fibroblasts lower levels of the catalytic subunits INTS4, INTS9 and INTS11 were observed on western blots, indicating that the integrity of the complex is disrupted. Northern blots showed significantly misprocessed levels of U1, U2 and U4. Pathway analysis (DAVID) of expression data (Affymetrix Gene Chip 1.0 ST exon arrays) of RNA extracted from patient fibroblasts showed enrichment of deregulated genes involved in mRNA splicing and posttranscriptional modification. Expression data of (developing) human brain structures (Allen Brain Atlas) show that expression of INTS8 peaks prenatally, especially in the ganglionic eminences, (sub)ventricular zone and hindbrain, similar to the developmental expression in mouse embryo (Emage databse). Interestingly, neuronal precursors from these areas migrate to the cortex and are compatible to affected regions in PNH and cerebellar hypoplasia in the patients. We propose that dysfunction of the Integrator Complex, through snRNA misprocessing and spliceosomal defects, leads to severely disrupted brain development in humans. We used RNA isolated from human cultured fibroblasts, cell-lines were obtained from 3 individuals with INTS8 mutations and from 3 unaffected individuals. R,Oegema Six Affymetrix Gene Chip 1.0 ST exon arrays (patients: 04RD83, 83RD247, 04RD84 ; controls: 81RD193, GMO2037C, 86RD677) were rma normalized on transcript level using the R package oligo (http://www.r-project.org). Top down regulated (n=402) or up regulated (n=281) genes with p values <0.02 were analyzed for enriched gene ontology terms (goterms_BP_all) using DAVID (medium stringency)(down: 329 DAVID IDs, up: 225 DAVID IDs).