ABSTRACT: Purpose: The goal of this study was to assess the status of splicing changes in microexons in the cortex of individuals with autism. Methods: We performed RiboZero Gold (rRNA depleted) 50bp PE RNA-seq in a larger set of case and control samples to define 12 autism and 12 control samples showing the greatest global differential gene expression change. These samples, which show differential expression of the splicing regulator SRRM4, were used to evaluate global splicing changes. Results: Within these samples, 126 of 504 (30%) detected alternative microexons display a mean ΔPSI > 10 between ASD and control subjects of which 113 (90%) also display neural-differential regulation. By contrast, only 825 of 15,405 (5.4%) longer (i.e. >27 nt) exons show such misregulation, of which 285 (35%) correspond to neural-regulated exons. Notably, we also observe significantly higher correlations between microexon inclusion and nSR100 mRNA expression levels across the stratified ASD samples and controls, for those microexons regulated by nSR100 relative to those microexons that are not regulated by this factor (p=1.4×10-7, Wilcoxon Sum Rank test). Conclusions: These data suggest microexon regulation is a potentially important mechanism underlying ASD and likely other neurodevelopmental disorders
Project description:Purpose: The goal of this study was to assess the status of splicing changes in microexons in the cortex of individuals with autism. Methods: We performed RiboZero Gold (rRNA depleted) 50bp PE RNA-seq in a larger set of case and control samples to define 12 autism and 12 control samples showing the greatest global differential gene expression change. These samples, which show differential expression of the splicing regulator SRRM4, were used to evaluate global splicing changes. Results: Within these samples, 126 of 504 (30%) detected alternative microexons display a mean ?PSI > 10 between ASD and control subjects of which 113 (90%) also display neural-differential regulation. By contrast, only 825 of 15,405 (5.4%) longer (i.e. >27 nt) exons show such misregulation, of which 285 (35%) correspond to neural-regulated exons. Notably, we also observe significantly higher correlations between microexon inclusion and nSR100 mRNA expression levels across the stratified ASD samples and controls, for those microexons regulated by nSR100 relative to those microexons that are not regulated by this factor (p=1.4×10-7, Wilcoxon Sum Rank test). Conclusions: These data suggest microexon regulation is a potentially important mechanism underlying ASD and likely other neurodevelopmental disorders 12 case samples representing a more extreme autism gene expression signature and 12 representative controls; raw data have been submitted to dbGaP
Project description:A key challenge in understanding and ultimately treating autism is to identify common molecular mechanisms underlying this genetically heterogeneous disorder. Transcriptomic profiling of autistic brains has revealed correlated misregulation of the neuronal splicing regulator nSR100/SRRM4 and its target microexon splicing program in more than one-third of analyzed individuals. To investigate whether nSR100 misregulation is causally linked to autism, we generated mutant mice with reduced levels of this protein and its target splicing program. Remarkably, these mice display multiple hallmark features of autism, including altered social behaviors, synaptic density and signaling. Moreover, increased neuronal activity, which is often associated with autism, results in a rapid decrease in nSR100 and splicing of microexons that significantly overlap those misregulated in autistic brains. Collectively, our results provide evidence that misregulation of an nSR100-dependent splicing network controlled by changes in neuronal activity is causally linked to a substantial fraction of autism cases.
Project description:Alternative splicing has critical roles in diverse cellular, developmental and pathological processes. However, the full repertoires of factors that control individual splicing events are not known. We describe a CRISPR-based screening strategy for the systematic identification of genes that control 3-27 nt microexons with functions in nervous system development and that are commonly disrupted in autism. Besides known regulators including nSR100/Srrm4, Rbfox and Ptbp1, approximately 200 additional genes impact microexon splicing. These genes are enriched in genetic links to autism. Two of the screen hits, Srsf11 and Rnps1, preferentially regulate Srrm4-dependent microexons relative to other exons. These factors form mutually stabilizing interactions with Srrm4 that bridge upstream intronic enhancer elements and exonic sequences to activate microexon splicing. Our study thus presents a system for the genome-wide definition of splicing regulatory networks and further reveals a mechanism for the recognition of microexons with critical roles in nervous system development and disorders.
Project description:Alternative splicing has critical roles in diverse cellular, developmental and pathological processes. However, the full repertoires of factors that control individual splicing events are not known. We describe a CRISPR-based screening strategy for the systematic identification of genes that control 3-27 nt microexons with functions in nervous system development and that are commonly disrupted in autism. Besides known regulators including nSR100/Srrm4, Rbfox and Ptbp1, approximately 200 additional genes impact microexon splicing. These genes are enriched in genetic links to autism. Two of the screen hits, Srsf11 and Rnps1, preferentially regulate Srrm4-dependent microexons relative to other exons. These factors form mutually stabilizing interactions with Srrm4 that bridge upstream intronic enhancer elements and exonic sequences to activate microexon splicing. Our study thus presents a system for the genome-wide definition of splicing regulatory networks and further reveals a mechanism for the recognition of microexons with critical roles in nervous system development and disorders.
Project description:Alternative splicing has critical roles in diverse cellular, developmental and pathological processes. However, the full repertoires of factors that control individual splicing events are not known. We describe a CRISPR-based screening strategy for the systematic identification of genes that control 3-27 nt microexons with functions in nervous system development and that are commonly disrupted in autism. Besides known regulators including nSR100/Srrm4, Rbfox and Ptbp1, approximately 200 additional genes impact microexon splicing. These genes are enriched in genetic links to autism. Two of the screen hits, Srsf11 and Rnps1, preferentially regulate Srrm4-dependent microexons relative to other exons. These factors form mutually stabilizing interactions with Srrm4 that bridge upstream intronic enhancer elements and exonic sequences to activate microexon splicing. Our study thus presents a system for the genome-wide definition of splicing regulatory networks and further reveals a mechanism for the recognition of microexons with critical roles in nervous system development and disorders.
Project description:Alternative splicing has critical roles in diverse cellular, developmental and pathological processes. However, the full repertoires of factors that control individual splicing events are not known. We describe a CRISPR-based screening strategy for the systematic identification of genes that control 3-27 nt microexons with functions in nervous system development and that are commonly disrupted in autism. Besides known regulators including nSR100/Srrm4, Rbfox and Ptbp1, approximately 200 additional genes impact microexon splicing. These genes are enriched in genetic links to autism. Two of the screen hits, Srsf11 and Rnps1, preferentially regulate Srrm4-dependent microexons relative to other exons. These factors form mutually stabilizing interactions with Srrm4 that bridge upstream intronic enhancer elements and exonic sequences to activate microexon splicing. Our study thus presents a system for the genome-wide definition of splicing regulatory networks and further reveals a mechanism for the recognition of microexons with critical roles in nervous system development and disorders.
Project description:Alternative splicing (AS) generates vast transcriptomic complexity in the vertebrate nervous system. However, the extent to which trans-acting splicing regulators and their target AS regulatory networks contribute to nervous system development is not completely understood. To address these questions, we have generated mice lacking the vertebrate- and neural-specific Ser/Arg-repeat related protein of 100 kDa (nSR100/SRRM4). Loss of nSR100 impairs development of the central and peripheral nervous systems, in part by disrupting neurite outgrowth, cortical layering in the forebrain, and axon guidance in the corpus callosum. Accompanying these developmental defects are widespread changes in AS that primarily result in shifts to non-neural patterns for different classes of splicing events. The main component of the altered AS program comprises 3-27 nucleotide neural microexons, an emerging class of highly conserved alternative splicing event associated with the regulation of protein interaction networks in developing neurons and neurological disorders. Remarkably, inclusion of a 6-nucleotide nSR100-activated microexon in Unc13b transcripts is sufficient to rescue a neuritogenesis defect in nSR100 mutant primary neurons. These results thus reveal critical in vivo neurodevelopmental functions of nSR100, and they further link these functions to a conserved program of neural microexon splicing. mRNA profiles of mouse control or nSR100/Srrm4 KO cortex or hippocampus using high-throughput sequencing data.
Project description:The mechanisms by which entire programs of gene regulation emerged during evolution are poorly understood. Neuronal microexons represent the most conserved class of alternative splicing in vertebrates and are critical for proper brain development and function. Here, we discover neural microexon programs in non-vertebrate species and trace their origin to bilaterian ancestors through the emergence of a previously uncharacterized ‘enhancer of microexons' (eMIC) protein domain. The eMIC domain originated as an alternative, neural-enriched splice isoform of the pan-eukaryotic Srrm2/SRm300 splicing factor gene, and subsequently became fixed in the vertebrate and neuronal-specific splicing regulator Srrm4/nSR100 and its paralog Srrm3. Remarkably, the eMIC domain is necessary and sufficient for microexon splicing, and functions by interacting with the earliest components required for exon recognition. The emergence of a novel domain with restricted expression in the nervous system thus resulted in the evolution of splicing programs that contributed to qualitatively expand neuronal molecular complexity in bilaterians.
Project description:Alternative splicing (AS) generates vast transcriptomic complexity in the vertebrate nervous system. However, the extent to which trans-acting splicing regulators and their target AS regulatory networks contribute to nervous system development is not completely understood. To address these questions, we have generated mice lacking the vertebrate- and neural-specific Ser/Arg-repeat related protein of 100 kDa (nSR100/SRRM4). Loss of nSR100 impairs development of the central and peripheral nervous systems, in part by disrupting neurite outgrowth, cortical layering in the forebrain, and axon guidance in the corpus callosum. Accompanying these developmental defects are widespread changes in AS that primarily result in shifts to non-neural patterns for different classes of splicing events. The main component of the altered AS program comprises 3-27 nucleotide neural microexons, an emerging class of highly conserved alternative splicing event associated with the regulation of protein interaction networks in developing neurons and neurological disorders. Remarkably, inclusion of a 6-nucleotide nSR100-activated microexon in Unc13b transcripts is sufficient to rescue a neuritogenesis defect in nSR100 mutant primary neurons. These results thus reveal critical in vivo neurodevelopmental functions of nSR100, and they further link these functions to a conserved program of neural microexon splicing.
Project description:Microexons represent the most highly conserved class of alternative splicing, yet their functions are poorly understood. Here, we focus on closely related neuronal microexons overlapping prion-like domains in the translation initiation factors, eIF4G1 and eIF4G3, the splicing of which is activity-dependent and frequently disrupted in autism. CRISPR-Cas9 deletion of these microexons selectively up-regulates synaptic proteins that control neuronal activity and plasticity and further triggers a gene expression program mirroring that of activated neurons. Mice lacking the Eif4g1 microexon display social behavior, learning and memory deficits, as well as alterations in hippocampal synaptic plasticity. The eIF4G microexons appear to reduce synaptic protein synthesis by causing ribosome stalling, through a mechanism whereby they promote the coalescence of cytoplasmic granule components associated with translation repression, including the Fragile X mental retardation protein, FMRP. The results thus reveal an autism-disrupted mechanism by which alternative splicing specializes translation to control higher-order cognitive functioning.