Project description:Topoisomerases are necessary for the expression of neurodevelopmental genes, and are mutated in some patients with autism spectrum disorder (ASD). We have studied the effects of inhibitors of Topoisomerase 1 (Top1) and Topoisomerase 2 (Top2) enzymes on mouse cortical neurons. We find that topoisomerases selectively inhibit long genes (>100kb), with little effect on all other gene expression. Using ChIPseq against RNA Polymerase II (Pol2) we show that the Top1 inhibitor topotecan blocks transcriptional elongation of long genes specifically. Many of the genes inhibited by topotecan are candidate ASD genes, leading us to propose that topoisomerase inhibition might contribute to ASD pathology.
Project description:Topoisomerases are necessary for the expression of neurodevelopmental genes, and are mutated in some patients with autism spectrum disorder (ASD). We have studied the effects of inhibitors of Topoisomerase 1 (Top1) and Topoisomerase 2 (Top2) enzymes on mouse cortical neurons. We find that topoisomerases selectively inhibit long genes (>100kb), with little effect on all other gene expression. Using ChIPseq against RNA Polymerase II (Pol2) we show that the Top1 inhibitor topotecan blocks transcriptional elongation of long genes specifically. Many of the genes inhibited by topotecan are candidate ASD genes, leading us to propose that topoisomerase inhibition might contribute to ASD pathology.
Project description:Topoisomerases are necessary for the expression of neurodevelopmental genes, and are mutated in some patients with autism spectrum disorder (ASD). We have studied the effects of inhibitors of Topoisomerase 1 (Top1) and Topoisomerase 2 (Top2) enzymes on mouse cortical neurons. We find that topoisomerases selectively inhibit long genes (>100kb), with little effect on all other gene expression. Using ChIPseq against RNA Polymerase II (Pol2) we show that the Top1 inhibitor topotecan blocks transcriptional elongation of long genes specifically. Many of the genes inhibited by topotecan are candidate ASD genes, leading us to propose that topoisomerase inhibition might contribute to ASD pathology. [Mouse] 5 biological replicates of transcriptome sequencing (RNAseq) from topotecan treated neurons and vehicle treated controls; Pol2 ChIPseq of topotecan and vehicle treated neurons [Human] Transcriptome sequencing (RNAseq) from topotecan treated neurons and vehicle treated control.
Project description:Topoisomerases are necessary for the expression of neurodevelopmental genes, and are mutated in some patients with autism spectrum disorder (ASD). We have studied the effects of inhibitors of Topoisomerase 1 (Top1) and Topoisomerase 2 (Top2) enzymes on mouse cortical neurons. We find that topoisomerases selectively inhibit long genes (>100kb), with little effect on all other gene expression. Using ChIPseq against RNA Polymerase II (Pol2) we show that the Top1 inhibitor topotecan blocks transcriptional elongation of long genes specifically. Many of the genes inhibited by topotecan are candidate ASD genes, leading us to propose that topoisomerase inhibition might contribute to ASD pathology. 9 experiments, gene expression measured by Affymetrix microarray. 1) cultured mouse cortical neurons treated with 300nM topotecan vs vehicle-treated controls 2) cultured mouse neurons treated with 1uM topotecan vs vehicle-treated controls 3) cultured mouse cortical neurons treated with 3uM ICRF-193 vs vehicle-treated controls. 4) cultured mouse cortical neurons treated with 10 uM irinotecan vs vehicle-treated controls. 5) cultured mouse cortical neurons treated with 3-1000 nM topotecan vs vehicle treated controls 6) cultured mouse cortical neurons treated with lentivirus expressing shRNA against Top1 and Top2b vs scrambled shRNA controls 7) cultured mouse cortical neurons treated with DRB vs vehicle-treated controls 8) cultured mouse cortical neurons treated with hydrogen peroxide or paraquat vs vehicle-treated controls 9) cultured mouse cortical neurons treated with topotecan with or without subsequent drug washout, vs vehicle-treated controls.
Project description:Autism is currently considered a multigene disorder with epigenetic influences. To investigate the contribution of DNA methylation to autism spectrum disorders, we have recently completed large-scale methylation profiling by CpG island microarray analysis of lymphoblastoid cell lines (LCL) derived from monozygotic twins discordant for diagnosis of autism and their nonautistic siblings. Methylation profiling revealed many candidate genes differentially methylated between discordant MZ twins as well as between both twins and nonautistic siblings. Bioinformatics analysis of the differentially methylated genes demonstrated enrichment for high level functions including gene transcription, nervous system development, cell death/survival, and other biological processes implicated in autism. The methylation status of two of these candidate genes, BCL-2 and retinoic acid receptor (RAR)-related orphan receptor alpha (RORA), was further confirmed by bisulfite sequencing and methylation-specific PCR, respectively. Immunohistochemical analyses of tissue arrays containing slices of the cerebellum and frontal cortex of autistic and age- and sex-matched control subjects revealed decreased expression of RORA and BCL-2 proteins in the autistic brain. Our data thus confirm the role of epigenetic regulation of gene expression via differential DNA methylation in idiopathic autism, and furthermore link molecular changes in a peripheral cell model with brain pathobiology in autism. Global methylation profiling was performed on lymphoblastoid cell lines (LCLs) derived from three pairs of male monozygotic twins discordant for diagnosis of autism as determined by the Autism Diagnostic Interview-Revised (ADI-R). As controls, cell lines derived from non-autistic siblings of two pairs of twins were also included in the analyses, in addition to cell lines derived from a set of monozygotic twins unaffected by autism. For all paired analyses, a direct comparison was performed in which the methylation-enriched fractions from two individuals were pooled and hybridized onto the same microarray. In addition, indirect comparisons were performed by co-hybridizing the methylation-enriched (MIRA) fraction with the respective unenriched DNA fraction obtained from the same individual. For each paired analysis (between autistic MZ twins and/or between autistic co-twin and unaffected sibling), a total number of 4 replicates were performed, including direct and indirect comparisons.
Project description:To characterize the genetic basis of hybrid male sterility in detail, we used a systems genetics approach, integrating mapping of gene expression traits with sterility phenotypes and QTL. We measured genome-wide testis expression in 305 male F2s from a cross between wild-derived inbred strains of M. musculus musculus and M. m. domesticus. We identified several thousand cis- and trans-acting QTL contributing to expression variation (eQTL). Many trans eQTL cluster into eleven ‘hotspots,’ seven of which co-localize with QTL for sterility phenotypes identified in the cross. The number and clustering of trans eQTL - but not cis eQTL - were substantially lower when mapping was restricted to a ‘fertile’ subset of mice, providing evidence that trans eQTL hotspots are related to sterility. Functional annotation of transcripts with eQTL provides insights into the biological processes disrupted by sterility loci and guides prioritization of candidate genes. Using a conditional mapping approach, we identified eQTL dependent on interactions between loci, revealing a complex system of epistasis. Our results illuminate established patterns, including the role of the X chromosome in hybrid sterility.
Project description:Topoisomerases are crucial to solve DNA topological problems, but they have not been linked to RNA metabolism. Here we show that human topoisomerase 3β (Top3β) is an RNA topoisomerase that biochemically and genetically interacts with FMRP, a protein deficient in Fragile X syndrome and known to regulate translation of mRNAs important for neuronal function and autism. Notably, the FMRP-Top3β interaction is abolished by a disease-associated FMRP mutation, and several human genetic studies link Top3β mutation to schizophrenia and intellectual disability. Top3β binds multiple mRNAs encoded by genes with neuronal functions related to schizophrenia and autism. Expression of one such gene, ptk2/FAK, is reduced in neuromuscular junctions of Top3β mutant flies. Synapse formation is defective in Top3β mutant flies and mice, as observed in FMRP mutant animals. Our findings suggest that Top3β acts as an RNA topoisomerase and works with FMRP to promote expression of mRNAs critical for neurodevelopment and mental health.