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:The vertebrate and neural-specific SR-related protein nSR100/SRRM4 regulates an extensive program of alternative splicing with critical roles in nervous system development. However, the mechanism by which nSR100 controls its target exons is poorly understood. We demonstrate that nSR100-dependent neural exons are associated with a unique configuration of intronic cis-elements that promote rapid switch-like regulation during neurogenesis. A key feature of this configuration is the insertion of specialized intronic enhancers between polypyrimidine tracts and acceptor sites that bind nSR100 to potently activate exon inclusion in neural cells, while weakening 3' splice site recognition and contributing to exon skipping in non-neural cells. nSR100 further operates by forming multiple interactions with early spliceosome components bound proximal to 3' splice sites. These multifaceted interactions achieve dominance over neural exon silencing mediated by the splicing regulator PTBP1. The results thus illuminate a widespread mechanism by which a critical neural exon network is activated during neurogenesis. RNA-Seq was used to obtain mRNA profiles of various N2A and 293T cell lines from human and mouse, respectively, to investigate the roles of nSR100, Ptbp1 and U2af65 in alternative splicing regulation. PAR-iCLIP and iCLIP experiments followed by high throughput sequencing were conducted to obtain RNA binding profiles of nSR100, PTBP1 and U2af65.
Project description:The spontaneous mutant Bronx waltzer (bv) mouse line is characterized by deafness and balance defect. We located the bv mutation to the Srrm4 gene which encodes a regulator of alternative pre-mRNA splicing. We found that Srrm4 is expressed in balance and hearing organs (i.e. in the vestibular maculas and the cochlea). Srrm4 is also expressed in the central nervous system including the cerebellum. To identify potential splicing defects in bv/bv mice, we analyzed RNA samples from the vestibular maculas and cerebellums of bv/bv mice and control (bv/+) littermates, using mouse exon junction microarrays (MJAY). In this dataset, we include probe-set level data obtained from cerebellar samples. The processed data represent probe-set intensities that have been normalized to gene expression levels. 8 total samples were analyzed in this series: cerebellums from 4 heterozygous (bv/+) and 4 homozygous (bv/bv) mice at P15.
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 spontaneous mutant Bronx waltzer (bv) mouse line is characterized by deafness and balance defect. We located the bv mutation to the Srrm4 gene which encodes a regulator of alternative pre-mRNA splicing. We found that Srrm4 is expressed in balance and hearing organs (i.e. in the vestibular maculas and the cochlea). Srrm4 is also expressed in the central nervous system including the cerebellum. To identify potential splicing defects in bv/bv mice, we analyzed RNA samples from the vestibular maculas and cerebellums of bv/bv mice and control (bv/+) littermates, using mouse exon junction microarrays (MJAY). In this dataset, we include probe-set level data obtained from vestibular macula samples. The processed data represent probe-set intensities that have been normalized to gene expression levels (Inorm). Inorm was calculated using batch-corrected data as well as data that were not corrected for a batch effect. 7 total samples were analyzed: vestibular maculas from 4 heterozygous (bv/+) and 3 homozygous (bv/bv) mouse embryos at E16.5.
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:The spontaneous mutant Bronx waltzer (bv) mouse line is characterized by deafness and balance defect. We located the bv mutation to the Srrm4 gene which encodes a regulator of alternative pre-mRNA splicing. We found that Srrm4 is expressed in balance and hearing organs (i.e. in the vestibular maculas and the cochlea). Srrm4 is also expressed in the central nervous system including the cerebellum. To identify potential splicing defects in bv/bv mice, we analyzed RNA samples from the vestibular maculas and cerebellums of bv/bv mice and control (bv/+) littermates, using mouse exon junction microarrays (MJAY). In this dataset, we include probe-set level data obtained from cerebellar samples. The processed data represent probe-set intensities that have been normalized to gene expression levels.