Project description:The 5' untranslated region (UTR) sequence of eukaryotic mRNAs may contain upstream open reading frames (uORFs), which can regulate translation of the main open reading frame (mORF). The current model of translational regulation by uORFs posits that when a ribosome scans an mRNA and encounters a uORF, translation of that uORF can prevent ribosomes from reaching the mORF and cause decreased mORF translation. In this study, we first observed that rare variants in the 5' UTR dysregulate protein abundance. Upon further investigation, we found that rare variants near the start codon of uORFs can repress or derepress mORF translation, causing allelic changes in protein abundance. This finding holds for common variants as well, and common variants that modify uORF start codons also contribute disproportionately to metabolic and whole-plant phenotypes, suggesting that translational regulation by uORFs serves an adaptive function. These results provide evidence for the mechanisms by which natural sequence variation modulates gene expression, and ultimately, phenotype.
Project description:The X-chromosomal dystonia parkinsonism syndrome (XDP) is associated with sequence changes within the TAF1/DYT3 multiple transcript system. While most sequence changes are intronic, one, DSC3, is located within an exon (d4). Transcribed exon d4 occurs as part of multiple splice variants. These variants include exons d3 and d4 spliced to exons of TAF1, and an independent transcript composed of exons d2-d4. Location of DSC3 in an exon (d4) and utilization of this exon in multiple splice variants suggests an important role of DSC3 in the pathogenesis of XDP. To test this hypothesis we transfected neuroblastoma cells with four expression constructs, including exons d2-d4 (d2-d4/wild-type (wt) and d2-d4/DSC3) and d3-d4 (d3-d4/wt and d3-d4/DSC3). Expression profiling revealed a dramatic effect of DSC3 on overall gene expression. 362 genes differ between cells containing d2-d4/wt and d2-d4/DSC3. Annotation clustering revealed high enrichment of genes related to dopamine metabolism, vesicular transport, synapse function, Ca++ metabolism, and oxidative stress. 211 genes were differentially expressed in d3-d4/wt vs. d3-d4/DSC3. Annotation clustering highlighted genes in signal transduction and cell-cell interaction. The data shows an important role of physiologically occurring transcript d2-d4 in normal brain function. Interference with this role by DSC3 is a likely pathological mechanism in XDP. Disturbance of dopamine function and of Ca++ metabolism can explain abnormal movement; loss of protection against reactive oxygen species may account for the neurodegenerative changes in XDP. Although d3-d4 also affect genes potentially related to neurodegenerative processes their physiologic role as splice variants of TAF1 awaits further exploration. We transfected neuroblastoma cells with four expression constructs, including exons d2-d4 (d2-d4/wild-type (wt) and d2-d4/DSC3) and d3-d4 (d3-d4/wt and d3-d4/DSC3).
Project description:Here, we examined de novo variants identified within annotated 3′UTRs from the whole-genome sequencing of 519 families from the Simons Simplex Collection (Werling et al., 2018), totaling 342 mutations from probands and 299 from unaffected siblings within the same cohort. For each variant we synthesized an allelic pair of 3′UTR ‘elements’ spanning 120 bp of sequence centered on the variant. To be able to compare biological to non-biological sequences, for 322 variants, we randomly shuffled the sequence to generate a set of GC-matched controls. We tagged all 1,624 elements with six unique barcodes to provide internal replicates and control for potential barcode effects. To enable eventual cell-type specific studies, we cloned the final library of 9,744 synthesized oligos into the 3′UTR of a membrane-localized tdTomato reporter embedded in a Double-floxed inverse Orientation (DiO) cassette (Schnütgen et al., 2003), such that the reporter library would only express following Cre-mediated recombination. We completed the analysis of this library in vitro in N2a cells and in vivo in Vglut-Cre mice. Additional code and results corresponding to this GEO submission can be found at https://bitbucket.org/jdlabteam/asd_3utr_mpra_analysis/src/master/
Project description:Multiple regulatory layers influence allele-specific expression (ASE), particularly through sequence-dependent and parent-of-origin-dependent mechanisms at the transcriptional level. However, little is known about allele-specific gene regulation at the post-transcriptional level. Here, we conduct transcriptome-wide analysis of allele-specific m6A in mice. Using early postnatal cerebellum and cerebrum samples from reciprocal crosses of two divergent mouse strains, we employed quantitative m6A assays to measure allelic differences in m6A at single-base resolution. Our study reveals widespread sequence-dependent allelic imbalance in m6A methylation, identifying thousands of allele-specific m6A (ASm6A) sites with statistically significant and reproducible allelic methylation differences across diverse samples. We find evidence of potential cis-regulatory variants within 50-nt flanking regions of these ASm6A sites, with the highest enrichment at the motif positions. Intriguingly, we detect parental effects on allelic methylation across m6A sites exhibiting parent-of-origin-dependent ASE. For both sequence- and parent-of-origin-dependent allelic m6A methylation, we observe opposing allelic preferences between methylation and expression, suggesting a potential role of ASm6A in regulating ASE through negative effects on gene expression. Overall, our findings reveal that both cis-acting and parent-of-origin effects influence ASm6A, offering new insights into post-transcriptional mechanisms of ASE regulation.
Project description:Multiple regulatory layers influence allele-specific expression (ASE), particularly through sequence-dependent and parent-of-origin-dependent mechanisms at the transcriptional level. However, little is known about allele-specific gene regulation at the post-transcriptional level. Here, we conduct transcriptome-wide analysis of allele-specific m6A in mice. Using early postnatal cerebellum and cerebrum samples from reciprocal crosses of two divergent mouse strains, we employed quantitative m6A assays to measure allelic differences in m6A at single-base resolution. Our study reveals widespread sequence-dependent allelic imbalance in m6A methylation, identifying thousands of allele-specific m6A (ASm6A) sites with statistically significant and reproducible allelic methylation differences across diverse samples. We find evidence of potential cis-regulatory variants within 50-nt flanking regions of these ASm6A sites, with the highest enrichment at the motif positions. Intriguingly, we detect parental effects on allelic methylation across m6A sites exhibiting parent-of-origin-dependent ASE. For both sequence- and parent-of-origin-dependent allelic m6A methylation, we observe opposing allelic preferences between methylation and expression, suggesting a potential role of ASm6A in regulating ASE through negative effects on gene expression. Overall, our findings reveal that both cis-acting and parent-of-origin effects influence ASm6A, offering new insights into post-transcriptional mechanisms of ASE regulation.
Project description:Primary objectives: To observe the correlation between ABCB1 polymorphisms in Exons 13, 22 and 27 and the clearance of sunitinib at steady state.
Primary endpoints: The endpoint of the study is a correlation between sunitinib clearance and toxicityadjusteddose with ABCB1 genotype examining SNPs in exons 13, 22,and 27 as wellas haplotypes of these exons.
Project description:Eosinophilic esophagitis (EoE) is a rare atopic disorder associated with esophageal dysfunction, including difficulty swallowing, food impaction, and inflammation. EoE develops in a small subset of people with food allergies under the influence of environmental and genetic risk factors. Genome wide association studies (GWAS) have identified 31 independent risk loci for the disease, and linkage disequilibrium (LD) expansion of these loci nominates a set of 531 variants that are potentially causal. These risk variants are non-coding, suggesting a likely role in altered gene regulatory mechanisms. To systematically interrogate the gene regulatory activity of these variants, we designed a massively parallel reporter assay (MPRA) containing the alleles of each variant within their 170 bp genomic sequence context cloned into a GFP reporter library. Transfection of the MPRA library into TE-7 esophageal epithelial cells, HaCaT skin keratinocytes, and Jurkat T cells revealed cell-type-specific gene regulation. We identify 32 allelic enhancer variants (allelic enVars) that regulate reporter gene expression in a genotype-dependent manner in at least one cellular context. By annotating these variants with expression quantitative trait loci (eQTL) and chromatin looping data in related tissues and cell types, we identify putative target genes affected by genetic variation in EoE patients, including TSLP and multiple genes at the HLA locus. Transcription factor enrichment analyses reveal possible roles for cell-type specific regulators, including GATA-3, a key regulator of type 2 inflammation. Collectively, our approach reduces the large set of EoE-associated variants to a set of 32 with allelic regulatory activity, providing new functional insights into the effects of genetic variation in this disease.
Project description:Eosinophilic esophagitis (EoE) is a rare atopic disorder associated with esophageal dysfunction, including difficulty swallowing, food impaction, and inflammation. EoE develops in a small subset of people with food allergies under the influence of environmental and genetic risk factors. Genome wide association studies (GWAS) have identified 31 independent risk loci for the disease, and linkage disequilibrium (LD) expansion of these loci nominates a set of 531 variants that are potentially causal. These risk variants are non-coding, suggesting a likely role in altered gene regulatory mechanisms. To systematically interrogate the gene regulatory activity of these variants, we designed a massively parallel reporter assay (MPRA) containing the alleles of each variant within their 170 bp genomic sequence context cloned into a GFP reporter library. Transfection of the MPRA library into TE-7 esophageal epithelial cells, HaCaT skin keratinocytes, and Jurkat T cells revealed cell-type-specific gene regulation. We identify 32 allelic enhancer variants (allelic enVars) that regulate reporter gene expression in a genotype-dependent manner in at least one cellular context. By annotating these variants with expression quantitative trait loci (eQTL) and chromatin looping data in related tissues and cell types, we identify putative target genes affected by genetic variation in EoE patients, including TSLP and multiple genes at the HLA locus. Transcription factor enrichment analyses reveal possible roles for cell-type specific regulators, including GATA-3, a key regulator of type 2 inflammation. Collectively, our approach reduces the large set of EoE-associated variants to a set of 32 with allelic regulatory activity, providing new functional insights into the effects of genetic variation in this disease.
Project description:The X-chromosomal dystonia parkinsonism syndrome (XDP) is associated with sequence changes within the TAF1/DYT3 multiple transcript system. While most sequence changes are intronic, one, DSC3, is located within an exon (d4). Transcribed exon d4 occurs as part of multiple splice variants. These variants include exons d3 and d4 spliced to exons of TAF1, and an independent transcript composed of exons d2-d4. Location of DSC3 in an exon (d4) and utilization of this exon in multiple splice variants suggests an important role of DSC3 in the pathogenesis of XDP. To test this hypothesis we transfected neuroblastoma cells with four expression constructs, including exons d2-d4 (d2-d4/wild-type (wt) and d2-d4/DSC3) and d3-d4 (d3-d4/wt and d3-d4/DSC3). Expression profiling revealed a dramatic effect of DSC3 on overall gene expression. 362 genes differ between cells containing d2-d4/wt and d2-d4/DSC3. Annotation clustering revealed high enrichment of genes related to dopamine metabolism, vesicular transport, synapse function, Ca++ metabolism, and oxidative stress. 211 genes were differentially expressed in d3-d4/wt vs. d3-d4/DSC3. Annotation clustering highlighted genes in signal transduction and cell-cell interaction. The data shows an important role of physiologically occurring transcript d2-d4 in normal brain function. Interference with this role by DSC3 is a likely pathological mechanism in XDP. Disturbance of dopamine function and of Ca++ metabolism can explain abnormal movement; loss of protection against reactive oxygen species may account for the neurodegenerative changes in XDP. Although d3-d4 also affect genes potentially related to neurodegenerative processes their physiologic role as splice variants of TAF1 awaits further exploration.
Project description:Precise control of protein synthesis by engineering sequence elements in 5’ untranslated region (5’UTR) remains a fundamental challenge. To accelerate our understanding of cis-regulatory code embedded in 5’UTR, we devised massively parallel reporter assays from a synthetic mRNA library composed of over one million 5’UTR variants. A completely randomized 10-nucleotide sequence preceding an upstream open reading frame (uORF) and downstream GFP leads to a broad range of mRNA translatability and stability in mammalian cells. While efficient translation protects mRNA from degradation, uORF translation triggers mRNA decay in a UPF1-dependent manner. We also identified translational inhibitory elements in 5’UTR with G-quadruplex as a mark for mRNA decay in the P-body. Unexpectedly, an unstructured A-rich element in 5’UTR, while enabling cap-independent translation, destabilizes mRNAs in the absence of translation. Our results not only expose diverse sequence features of 5’UTR in controlling mRNA translatability, but also reveal ribosome-dependent and -independent mRNA surveillance pathways.