Project description:To assess the requirement of Nova2 for alternative processing of RNA in the developping brain. Neuronal migration leads to a highly organized laminar structure in the mammalian brain and its mis-regulation causes lissencephaly, behavioral and cognitive defects. Reelin signaling, mediated in part by a key adaptor, disabled-1 (Dab1), plays a critical but incompletely understood role in this process. We found that the neuron-specific RNA binding protein Nova2 regulates neuronal migration in late-generated cortical and Purkinje neurons. An unbiased HITS-CLIP and exon junction array search for Nova-dependent RNAs at E14.5 focused on components of the reelin pathway revealed only one candidate—an alternatively spliced isoform of Dab1 (Dab1.7bc). In utero electroporation demonstrated that Dab1.7bc was sufficient to induce neuronal migration defects in wild-type mice and exacerbate defects when Dab1 levels were reduced, while Dab1 overexpression mitigates defects in Nova2-null mice. Thus Nova2 regulates an RNA switch controlling the ability of Dab1 to mediate neuronal responsiveness to reelin signaling and neuronal migration, suggesting new links between splicing regulation, brain disease and development. Keywords: Comparative analysis RNA from the cortex of 3 wild type and 3 Nova2 KO E14.5 cortex. One array per biological replicate.
Project description:Proper cortical development relies on the balance of neuronal migration and proliferation. We investigated the gene expression differences of mouse knock-outs for Lissencephaly in humans. Our analysis suggests that gene expression and pathway analysis in mouse models of a similar disorder or within a common pathway can be used to define novel candidates for related human diseases. We investigated the developing brain of four mutants and wild-type mice using expression microarrays, bioinformatic analyses, and in vivo/in vitro experiments to address whether mutations in different members of the LIS1 neuronal migration complex lead to similar and/or distinct global gene expression alterations.
Project description:Reciprocal deletion and duplication of 16p11.2 is the most common copy number variation (CNV) associated with Autism Spectrum Disorder (ASD) and other developmental disorders, and has significant effect on brain size. We used cortical organoids derived from ASD cases to investigate neurodevelopmental pathways dysregulated by dosage changes of 16p11.2 CNV. We show that organoids recapitulate patients’ macrocephaly and microcephaly phenotypes. Deletions and duplications have “mirror” effects on cell proliferation, maturation and synapse number, consistent with “mirror” effects on brain development in humans. Neuronal migration was decreased in both, deletion and duplication organoids. Transcriptomic and proteomic profiling revealed synaptic defects and neuronal migration as key drivers of 16p11.2 functional effect. We implicate upregulation of small GTPase RhoA involved in regulation of cytoskeletal dynamics, neuron migration and neurite outgrowth as one of the pathways impacted by the 16p11.2 CNV in ASD. Treatment with the RhoA inhibitor Rhosin rescued neuron migration, but not synaptic defects. This study identifies pathways dysregulated by the 16p11.2 CNV during early neocortical development using cortical organoid models. Grant ID: Simons Foundation, #345469 Grant Title: Translational dysregulation of the RhoA pathway in autism Affiliation: University of California San Diego Name: Lilia M. Iakoucheva; Alysson R. Muotri
Project description:To assess the requirement of Nova2 for alternative processing of RNA in the developping brain. Neuronal migration leads to a highly organized laminar structure in the mammalian brain and its mis-regulation causes lissencephaly, behavioral and cognitive defects. Reelin signaling, mediated in part by a key adaptor, disabled-1 (Dab1), plays a critical but incompletely understood role in this process. We found that the neuron-specific RNA binding protein Nova2 regulates neuronal migration in late-generated cortical and Purkinje neurons. An unbiased HITS-CLIP and exon junction array search for Nova-dependent RNAs at E14.5 focused on components of the reelin pathway revealed only one candidate—an alternatively spliced isoform of Dab1 (Dab1.7bc). In utero electroporation demonstrated that Dab1.7bc was sufficient to induce neuronal migration defects in wild-type mice and exacerbate defects when Dab1 levels were reduced, while Dab1 overexpression mitigates defects in Nova2-null mice. Thus Nova2 regulates an RNA switch controlling the ability of Dab1 to mediate neuronal responsiveness to reelin signaling and neuronal migration, suggesting new links between splicing regulation, brain disease and development. Keywords: Comparative analysis
Project description:The subcommissural organ (SCO) is an ancient and evolutionarily conserved gland in the brain located at the entrance of the aqueduct of Sylvius. It exists in species as distantly related as amphioxus and humans, but the function of the SCO is still mysterious. Comparison of transcriptomes between SCO and non-SCO brain regions revealed three unique genes, namely Sspo, Car3, and Spdef, that are highly enriched in the SCO. We generated the corresponding gene knock-in mouse strains utilizing the Cre/lox recombinase system for specific expression in SCO cells. Genetic ablation of SCO cells at embryonic stages with these strains revealed that SCO excision resulted in severe hydrocephalus and developmental defects in the brain. Abnormalities were also observed for neuronal migration and axon and dendrite development in the cerebral cortex. Taking advantage of non-targeted peptidomic analysis, we identified three SCO-derived peptides, namely thymosin beta 4 (Tβ4), thymosin beta 10 (Tβ10), and NP24. We found that these SCO peptides contributed to neurite development and neuronal survival in vitro. Indeed, application of a cocktail containing Tβ4, Tβ10 and NP24 to SCO-ablated brain ventricles substantially rescued their developmental defects. Our results demonstrate that SCO-derived peptides play critical roles in neuronal development.
Project description:Neurons are highly polarized cells with distinct protein compositions in axonal and dendritic compartments. Cellular mechanisms controlling polarized protein sorting have been described for mature nervous system but little is known about the segregation in newly differentiated neurons. In a forward genetic screen for regulators of Drosophila brain circuit development, we identified mutations in <span style="color: rgb(54, 54, 54); font-style: normal; font-weight: 400; background-color: rgb(245, 245, 245);">Serine Palmitoyltransferase </span>(SPT), an evolutionary conserved enzyme in sphingolipid biosynthesis. Here we show that reduced levels of sphingolipids in SPT mutants cause axonal morphology defects similar to loss of cell recognition molecule Dscam. Loss- and gain-of-function studies show that neuronal sphingolipids are critical to prevent aggregation of axonal and dendritic Dscam isoforms, thereby ensuring precise Dscam localization to support axon branch segregation. Furthermore, SPT mutations causing neurodegenerative HSAN-I disorder in humans also result in formation of stable Dscam aggregates and axonal branch phenotypes in Drosophila neurons, indicating a causal link between developmental protein sorting defects and neuronal dysfunction.
Project description:Human brain development is a complex process involving neural proliferation, differentiation, and migration which are directed by many essential cellular factors and drivers. Here, using the NetBID2 algorithm and developing human brain RNA sequencing(RNA-Seq) dataset, we identified synaptotagmin-like 3(SYTL3) as one of the top drivers of early human brain development. Interestingly, SYTL3 exhibited high activity but low expression in both early developmental human cortex and human embryonic stem cell(hESC)-derived neurons. Knockout of SYTL3(SYTL3 -KO) in human neurons or knockdown of Sytl3 in embryonic mouse cortex markedly promoted neuronal migration. Besides, SYTL3-KO caused an abnormal distribution of deep-layer neurons in brain organoids and reduced presynaptic neurotransmitter release in hESC-derived neurons. We further demonstrated that SYTL3-KO- accelerated neuronal migration was modulated by high expression of matrix metalloproteinases. Together, based on bioinformatics and biological experiments, we identified SYTL3 as a novel regulator of cortical neuronal migration in human and mouse developing brains.
Project description:Cell-based models of many neurological and psychiatric diseases, established by reprogramming patient somatic cells into human induced pluripotent stem cells (hiPSCs), have now been reported. While numerous reports have demonstrated that neuronal cells differentiated from hiPSCs are electrophysiologically active mature neurons, the âageâ of these cells relative to cells in the human brain remains unresolved. Comparisons of gene expression profiles of hiPSC-derived neural progenitor cells (NPCs) and neurons to the Allen BrainSpan Atlas indicate that hiPSC neural cells most resemble first trimester neural tissue. Consequently, we posit that hiPSC-derived neural cells may most accurately be used to model the early developmental defects that contribute to disease predisposition rather than the late features of the disease. Though the characteristic symptoms of schizophrenia SZ generally appear late in adolescence, it is now thought to be a neurodevelopmental condition, often predated by a prodromal period that can appear in early childhood. Postmortem studies of SZ brain tissue typically describe defects in mature neurons, such as reduced neuronal size and spine density in the prefrontal cortex and hippocampus, but abnormalities of neuronal organization, particularly in the cortex, have also been reported. We postulated that defects in cortical organization in SZ might result from abnormal migration of neural cells. To test this hypothesis, we directly reprogrammed fibroblasts from SZ patients into hiPSCs and subsequently differentiated these disorder-specific hiPSCs into NPCs. SZ hiPSC differentiated into forebrain NPCs have altered expression of a number of cellular adhesion genes and WNT signaling. Methods: We compared global transcription of forebrain NPCs from six control and four SZ patients by RNAseq. Results: Multi-dimensional scaling (MDS) resolved most SZ and control hiPSC NPC samples; 848 genes were significantly differentially expressed (FDR<0.01) Conclusions: The WNT signaling pathway was enriched 2-fold (fisher exact test p-value = 0.031). 1-2 independent differentiations (biological replicates) for each of four control and four schizophrenia patients were analyzed; samples were generated in parallel to neuron RNAseq data.
Project description:Cell-based models of many neurological and psychiatric diseases, established by reprogramming patient somatic cells into human induced pluripotent stem cells (hiPSCs), have now been reported. While numerous reports have demonstrated that neuronal cells differentiated from hiPSCs are electrophysiologically active mature neurons, the “age” of these cells relative to cells in the human brain remains unresolved. Comparisons of gene expression profiles of hiPSC-derived neural progenitor cells (NPCs) and neurons to the Allen BrainSpan Atlas indicate that hiPSC neural cells most resemble first trimester neural tissue. Consequently, we posit that hiPSC-derived neural cells may most accurately be used to model the early developmental defects that contribute to disease predisposition rather than the late features of the disease. Though the characteristic symptoms of schizophrenia (SCZD) generally appear late in adolescence, it is now thought to be a neurodevelopmental condition, often predated by a prodromal period that can appear in early childhood. Postmortem studies of SCZD brain tissue typically describe defects in mature neurons, such as reduced neuronal size and spine density in the prefrontal cortex and hippocampus, but abnormalities of neuronal organization, particularly in the cortex, have also been reported. We postulated that defects in cortical organization in SCZD might result from abnormal migration of neural cells. To test this hypothesis, we directly reprogrammed fibroblasts from SCZD patients into hiPSCs and subsequently differentiated these disorder-specific hiPSCs into NPCs. SCZD hiPSC differentiated into forebrain NPCs have altered expression of a number of cellular adhesion genes, reduced WNT signaling and aberrant cellular migration. 3 independent differentiations (biological replicates) for each of four control and four schizophrenic patients were analyzed.
Project description:This experiment was designed to characterize the temporal gene expression dynamics of differentiating human neural progenitor cells through time in culture. In vitro models of neuronal differentiation are emerging as an important tool for high-throughput and high-content screening in neurodevelopmental toxicology. However, little has been done to characterize normal temporal pathway dynamics of differentiation in vitro or to anchor processes captured in vitro to developmental processes in vivo that are vulnerable to toxicant perturbation. We cultured human neural progenitor cell (hNPCs) up to 21 days in differentiation conditions, examining changes in morphology, protein expression and global gene expression. Over time, hNPCs acquired morphological characteristics of mature neuronal networks and increased protein expression of neuronal markers, including beta tubulin III, MAP2, and alpha-synuclein. Significantly changed genes were organized according to temporal expression patterns using K-means clustering, revealing 3 phases of gene expression. Quantitative pathway analysis identified gene ontology (GO) terms enriched among genes expressed in each of these phases and created a quantitative summary of temporal pathway trends in vitro. These observations of morphology, protein and gene expression provide a timeline of progression through differentiation, facilitating identification of key phases of sensitivity. We compared gene expression in vitro with publicly available gene expression data from developing human brain tissue in vivo and found substantial concordance in relative gene expression intensity. Genes highly expressed in both samples were enriched for key processes of brain development, including proliferation, migration, differentiation, synapse formation, and neurotransmission. GO terms enriched among genes highly expressed only in vivo or only in vitro reveal important differences between systems. For example, genes highly expressed in vitro are enriched for more stress and apoptosis pathways. This analysis provides a temporal roadmap of in vitro neuronal differentiation and anchors gene expression patterns in vitro to gene expression during sensitive windows of in vivo development. By anchoring in vitro dynamics to in vivo reference points, this work clarifies the extent to which fundamental processes of brain development are captured in our model.