Non-coding Regions Of Genome Research Articles

Deciphering the mystery of CHNG3.

Congenital hypothyroidism (CH), characterized by insufficient thyroid hormone production due to abnormalities in the hypothalamic-pituitary-thyroid axis, is the most common congenital endocrine disorder. We previously conducted comprehensive genetic screening of 102 patients with permanent CH born in Kanagawa Prefecture, Japan and identified mutations in several genes in 19 CH patients, including defects in genes encoding dual oxidase 2, thyroglobulin, thyrotropin receptor, thyroid peroxidase, and paired-box 8. Despite these findings, approximately 80% of cases remain unexplained. CH pedigrees unexplained by known genetic forms of CH have been reported in the literature and registered as congenital hypothyroidism, nongoitrous, 3 (CHNG3; %609893) in Online Mendelian Inheritance in Man. We also identified a Japanese pedigree of CH that was compatible with CHNG3. However, the exact genetic cause of CHNG3 was not revealed by standard analysis methods such as exome sequencing and array comparative genomic hybridization. We therefore took a combined approach and analyzed a total of 11 undiagnosed CH pedigrees by whole genome sequencing to analyze a 3-Mb linkage region, and found a disease-causing variant affecting a TTTG microsatellite in a noncoding region on chromosome 15. Further analysis revealed that 13.9% of 989 Japanese CH patients had abnormalities involving the TTTG microsatellite, with a substantial proportion (41.5%) of familial CH cases carrying these mutations. Identification of the genetic cause of CHNG3 provides new insights into the pathogenesis of CH, and highlights the need for continued exploration of noncoding genomic regions in Mendelian disorders of unknown etiology.

Promoter Deletion Leading to Allele Specific Expression in a Genetically Unsolved Case of Primary Ciliary Dyskinesia.

Variation in the non-coding genome represents an understudied mechanism of disease and it remains challenging to predict if single nucleotide variants, small insertions and deletions, or structural variants in non-coding genomic regions will be detrimental. Our approach using complementary RNA-seq and targeted long-read DNA sequencing can prioritize identification of non-coding variants that lead to disease via alteration of gene splicing or expression. We have identified a patient with primary ciliary dyskinesia with a pathogenic coding variant on one allele of the SPAG1 gene, while the second allele appears normal by whole exome sequencing despite an autosomal recessive inheritance pattern. RNA sequencing revealed reduced SPAG1 transcript levels and exclusive allele specific expression of the known pathogenic allele, suggesting the presence of a non-coding variant on the second allele that impacts transcription. Targeted long-read DNA sequencing identified a heterozygous 3 kilobase deletion of the 5' untranslated region of SPAG1, overlapping the promoter and first non-coding exon. This non-coding deletion was missed by whole exome sequencing and gene-specific deletion/duplication analysis, highlighting the importance of investigating the non-coding genome in patients with "missing" disease-causing variation. This paradigm demonstrates the utility of both RNA and long-read DNA sequencing in identifying pathogenic non-coding variants in patients with unexplained genetic disease.

Transcription factor networks disproportionately enrich for heritability of blood cell phenotypes.

Most phenotype-associated genetic variants map to non-coding regulatory regions of the human genome. Moreover, variants associated with blood cell phenotypes are enriched in regulatory regions active during hematopoiesis. To systematically explore the nature of these regions, we developed a highly efficient strategy, Perturb-multiome, that makes it possible to simultaneously profile both chromatin accessibility and gene expression in single cells with CRISPR-mediated perturbation of a range of master transcription factors (TFs). This approach allowed us to examine the connection between TFs, accessible regions, and gene expression across the genome throughout hematopoietic differentiation. We discovered that variants within the TF-sensitive accessible chromatin regions, while representing less than 0.3% of the genome, show a ~100-fold enrichment in heritability across certain blood cell phenotypes; this enrichment is strikingly higher than for other accessible chromatin regions. Our approach facilitates large-scale mechanistic understanding of phenotype-associated genetic variants by connecting key cis-regulatory elements and their target genes within gene regulatory networks.

Early moderate prenatal alcohol exposure and maternal diet impact offspring DNA methylation across species.

Alcohol consumption in pregnancy can affect genome regulation in the developing offspring but results have been contradictory. We employed a physiologically relevant murine model of short-term moderate prenatal alcohol exposure (PAE) resembling common patterns of alcohol consumption in pregnancy in humans. Early moderate PAE was sufficient to affect site-specific DNA methylation in newborn pups without altering behavioural outcomes in adult littermates. Whole-genome bisulfite sequencing of neonatal brain and liver revealed stochastic influence on DNA methylation that was mostly tissue-specific, with some perturbations likely originating as early as gastrulation. DNA methylation differences were enriched in non-coding genomic regions with regulatory potential indicative of broad effects of alcohol on genome regulation. Replication studies in human cohorts with fetal alcohol spectrum disorder suggested some effects were metastable at genes linked to disease-relevant traits including facial morphology, intelligence, educational attainment, autism, and schizophrenia. In our murine model, a maternal diet high in folate and choline protected against some of the damaging effects of early moderate PAE on DNA methylation. Our studies demonstrate that early moderate exposure is sufficient to affect fetal genome regulation even in the absence of overt phenotypic changes and highlight a role for preventative maternal dietary interventions.

Abstract 74: The rs1173771 Haplotype Associated with Blood Pressure Influences Chromatin Interactions Involving the Natriuretic Peptide Receptor 3 Gene Promoter

Determining the mechanisms of action for human blood pressure (BP) variants in the noncoding regions of genome, particularly large haplotypes containing multiple variants, is both critical and challenging. Human BP-associated rs1173771 locus includes a haplotype containing 11 single nucleotide polymorphisms (SNPs) spanning 17.4 kbp. The Linkage Disequilibrium (LD) region is approximately 126 kbp from the transcription start site of the closest protein-coding gene NPR3 (natriuretic peptide receptor 3). We used genome editing and region-capture Micro-C to examine the effect of the rs1173771 haplotype on the expression of neighboring genes and the chromatin mechanisms involved. The BP-elevating and -lowering haplotypes of rs1173771 locus were precisely reconstituted in human induced pluripotent stem cells (iPSCs) using an efficient, two-step genome editing technique. We then differentiated the edited iPSCs to endothelial (iEC) and vascular smooth muscle cells (iVSMC). The BP-elevating haplotype significantly (p ≤ 0.05) decreased NPR3 expression in iEC and iVSMC. Using region capture Micro-C targeting the rs1173771 haplotype region and the promoter regions of neighboring genes, we found in both iECs and iVSMCs, the BP-elevating rs1173771 haplotype increased chromatin contacts between the rs1173771 haplotype region and NPR3 promoter region, compared to the BP-lowering haplotype. Statistical comparison of chromatin interaction using HiCCompare showed the interactions of a genomic segment overlapping the 5’ end of the rs1173771 haplotype region with the NPR3 promoter region and a region just upstream of the promoter were 10 and 6 fold stronger (p.adj ≤ 0.001) in iECs with homozygous BP-elevating haplotype compared to BP-lowering haplotype. Similarly, in iVSMCs, the interaction of a genomic segment overlapping the rs1173771 haplotype region with a region just upstream of the NPR3 promoter was 4 fold stronger (p.adj = 0.02) for homozygous BP-elevating haplotype compared to BP-lowering haplotype. These results suggest that the BP-elevating rs1173771 haplotype interacts with the NPR3 promoter more strongly to suppress NPR3 expression, possibly through the recruitment of inhibitory protein complexes.

Abstract P364: Chromatin Interactions Between Regulatory Elements Influence Gene Expression in Human iPSC-Derived Endothelial and Vascular Smooth Muscle Cells

Most SNPs associated with blood pressure (BP) are located in noncoding regions of the human genome, where they may regulate gene expression in BP-relevant cell types. However, the mechanisms by which these SNPs influence BP regulation are unclear. To address this, we developed comprehensive epigenomic landscapes in human induced pluripotent stem cell (iPSC)-derived endothelial cells (iECs) and vascular smooth muscle cells (iVSMCs), incorporating DNA methylation analysis (RRBS), transcriptome analysis (RNA-seq), chromatin state profiling (ATAC-seq), and chromatin interaction mapping (Micro-C). We identified 5301, 8916, and 6046 chromatin loops in iECs and 5329, 7598, and 5228 loops in iVSMCs at 4, 8, and 16 kb resolutions (FDR < 0.05) respectively based on the Micro-C analysis. Remarkably, 82.4% and 83.8% of these chromatin contact regions in iECs and iVSMCs, respectively, harbored at least one known regulatory element such as an enhancer, promoter, or transcription factor binding site. Notably, 109 and 119 BP-associated SNPs were found within the chromatin contact regions of iECs and iVSMCs, respectively. We further investigated chromatin contact regions that involved interactions of regulatory elements. In both iECs and iVSMCs, lower methylation levels were observed in chromatin contact regions involving promoter-promoter (PP) and enhancer-promoter (EP) interactions, compared to enhancer-enhancer (EE), enhancer-transcription factor binding site (ET), and promoter-transcription factor binding site (PT) interactions. Additionally, greater chromatin accessibility was observed in chromatin contact regions involving PP and EP interactions. BP-associated SNPs were significantly enriched in chromatin contact regions involving PP and EP interactions. Moreover, genes proximal to chromatin contact regions involving PP or EP interactions exhibited higher expression than those near EE or other regulatory element interactions. These findings offer new insights into how chromatin interactions between regulatory elements define transcriptional states in human endothelial and vascular smooth muscle cells, providing a novel basis for understanding the genetic regulation of BP.

The evolution of ovarian somatic cells characterized by transcriptome and chromatin accessibility across rodents, monkeys, and humans

Abstract The ovary plays a crucial role in the reproductive system of female mammals by producing mature oocytes through folliculogenesis. Non-human model organisms are extensively utilized in research on human ovarian biology, thus necessitating the investigation of conservation and divergence in molecular mechanisms across species. In this study, we employed integrative single-cell analysis of transcriptome and chromatin accessibility to identify the evolutionary conservation and divergence patterns of ovaries among humans, monkeys, mice, rats, and rabbits. Our analyses revealed that theca cells exhibited the most significant changes during evolution based on scRNA-seq and scATAC-seq datasets. Furthermore, we discovered common cis-regulatory architectures in theca cells across species by conducting joint analyses of scRNA-seq and scATAC-seq datasets. These findings have potential applications in non-human biomedical and genetic research to validate molecular mechanisms found in human organisms. Additionally, our investigation into non-coding genomic regions identified intergenic highly transcribed regions (igHTRs) that may contribute to the evolution of species-specific phenotypic traits. Overall, our study provides valuable insights into understanding the molecular characteristics of adult ovaries while offering new perspectives for studying human ovarian physiology and diseases.

Exploring the Dark Matter of Human Proteome: The Emerging Role of Non-Canonical Open Reading Frame (ncORF) in Cancer Diagnosis, Biology, and Therapy.

Cancer develops from abnormal cell growth in the body, causing significant mortalities every year. To date, potent therapeutic approaches have been developed to eradicate tumor cells, but intolerable toxicity and drug resistance can occur in treated patients, limiting the efficiency of existing treatment strategies. Therefore, searching for novel genes critical for cancer progression and therapeutic response is urgently needed for successful cancer therapy. Recent advances in bioinformatics and proteomic techniques have allowed the identification of a novel category of peptides encoded by non-canonical open reading frames (ncORFs) from historically non-coding genomic regions. Surprisingly, many ncORFs express functional microproteins that play a vital role in human cancers. In this review, we provide a comprehensive description of different ncORF types with coding capacity and technological methods in discovering ncORFs among human genomes. We also summarize the carcinogenic role of ncORFs such as pTINCR and HOXB-AS3 in regulating hallmarks of cancer, as well as the roles of ncORFs such as HOXB-AS3 and CIP2A-BP in cancer diagnosis and prognosis. We also discuss how ncORFs such as AKT-174aa and DDUP are involved in anti-cancer drug response and the underestimated potential of ncORFs as therapeutic targets.

Ancestral Sequence Reconstruction as a Tool to Detect and Study De Novo Gene Emergence.

New protein-coding genes can evolve from previously noncoding genomic regions through a process known as de novo gene emergence. Evidence suggests that this process has likely occurred throughout evolution and across the tree of life. Yet, confidently identifying de novo emerged genes remains challenging. Ancestral sequence reconstruction is a promising approach for inferring whether a gene has emerged de novo or not, as it allows us to inspect whether a given genomic locus ancestrally harbored protein-coding capacity. However, the use of ancestral sequence reconstruction in the context of de novo emergence is still in its infancy and its capabilities, limitations, and overall potential are largely unknown. Notably, it is difficult to formally evaluate the protein-coding capacity of ancestral sequences, particularly when new gene candidates are short. How well-suited is ancestral sequence reconstruction as a tool for the detection and study of de novo genes? Here, we address this question by designing an ancestral sequence reconstruction workflow incorporating different tools and sets of parameters and by introducing a formal criterion that allows to estimate, within a desired level of confidence, when protein-coding capacity originated at a particular locus. Applying this workflow on ∼2,600 short, annotated budding yeast genes (<1,000 nucleotides), we found that ancestral sequence reconstruction robustly predicts an ancient origin for the most widely conserved genes, which constitute "easy" cases. For less robust cases, we calculated a randomization-based empirical P-value estimating whether the observed conservation between the extant and ancestral reading frame could be attributed to chance. This formal criterion allowed us to pinpoint a branch of origin for most of the less robust cases, identifying 49 genes that can unequivocally be considered de novo originated since the split of the Saccharomyces genus, including 37 Saccharomyces cerevisiae-specific genes. We find that for the remaining equivocal cases we cannot rule out different evolutionary scenarios including rapid evolution, multiple gene losses, or a recent de novo origin. Overall, our findings suggest that ancestral sequence reconstruction is a valuable tool to study de novo gene emergence but should be applied with caution and awareness of its limitations.

HyperCas12a enables highly-multiplexed epigenome editing screens.

Interactions between multiple genes or cis-regulatory elements (CREs) underlie a wide range of biological processes in both health and disease. High-throughput screens using dCas9 fused to epigenome editing domains have allowed researchers to assess the impact of activation or repression of both coding and non-coding genomic regions on a phenotype of interest, but assessment of genetic interactions between those elements has been limited to pairs. Here, we combine a hyper-efficient version of Lachnospiraceae bacterium dCas12a (dHyperLbCas12a) with RNA Polymerase II expression of long CRISPR RNA (crRNA) arrays to enable efficient highly-multiplexed epigenome editing. We demonstrate that this system is compatible with several activation and repression domains, including the P300 histone acetyltransferase domain and SIN3A interacting domain (SID). We also show that the dCas12a platform can perform simultaneous activation and repression using a single crRNA array via co-expression of multiple dCas12a orthologues. Lastly, demonstrate that the dCas12a system is highly effective for high-throughput screens. We use dHyperLbCas12a-KRAB and a ~19,000-member barcoded library of crRNA arrays containing six crRNAs each to dissect the independent and combinatorial contributions of CREs to the dose-dependent control of gene expression at a glucocorticoid-responsive locus. The tools and methods introduced here create new possibilities for highly multiplexed control of gene expression in a wide variety of biological systems.

DNA Transposons Favor De Novo Transcript Emergence Through Enrichment of Transcription Factor Binding Motifs.

De novo genes emerge from noncoding regions of genomes via succession of mutations. Among others, such mutations activate transcription and create a new open reading frame (ORF). Although the mechanisms underlying ORF emergence are well documented, relatively little is known about the mechanisms enabling new transcription events. Yet, in many species a continuum between absent and very prominent transcription has been reported for essentially all regions of the genome. In this study, we searched for de novo transcripts by using newly assembled genomes and transcriptomes of seven inbred lines of Drosophila melanogaster, originating from six European and one African population. This setup allowed us to detect sample specific de novo transcripts, and compare them to their homologous nontranscribed regions in other samples, as well as genic and intergenic control sequences. We studied the association with transposable elements (TEs) and the enrichment of transcription factor motifs upstream of de novo emerged transcripts and compared them with regulatory elements. We found that de novo transcripts overlap with TEs more often than expected by chance. The emergence of new transcripts correlates with regions of high guanine-cytosine content and TE expression. Moreover, upstream regions of de novo transcripts are highly enriched with regulatory motifs. Such motifs are more enriched in new transcripts overlapping with TEs, particularly DNA TEs, and are more conserved upstream de novo transcripts than upstream their 'nontranscribed homologs'. Overall, our study demonstrates that TE insertion is important for transcript emergence, partly by introducing new regulatory motifs from DNA TE families.

Unraveling the complex evolutionary features of the Cinnamomum camphora mitochondrial genome.

We reported the mitochondrial genome of Cinnamomum camphora for the first time, revealing frequent rearrangement events in the non-coding regions of Magnoliids mitochondrial genomes. As one of the representative species in the Lauraceae family of Magnoliids, Cinnamomum camphora holds significant economic and ecological value. In this study, the mitochondrial genome (mitogenome) of C. camphora was complete assembled and annotated using PacBio HiFi sequencing. The C. camphora mitogenome is characterized by a branch structure, spans 900,894 bp, and contains 43 protein-coding genes (PCGs), 24 tRNAs, and 3 rRNAs. Most of these PCGs are under purifying selection, with only two (ccmFc and rps7) exhibiting signs of positive selection. The C. camphora mitogenome contains numerous repetitive sequences and intracellular gene transfers, with a total of 36 mitochondrial plastid DNAs, amounting to a combined length of 23,816 bp. Comparative analysis revealed that the non-coding regions of Magnoliids mitogenomes have undergone frequent rearrangements during evolution, but the coding sequences remain highly conserved (more than 98% similarity for protein-coding sequences). Furthermore, a maximum-likelihood phylogenetic tree was reconstructed based on 25 PCGs from 23 plant mitogenomes. The analysis supports the closest relationship between C. camphora and C. chekiangense, consistent with the APG IV classification system. This study elucidates the unique evolutionary features of the C. camphora mitogenome, which will provide valuable insights into the study of genetics and evolution of the family Lauraceae.

Differential impact of quiescent non-coding loci on chromatin entropy.

Non-coding regions of the human genome are important for functional regulations, but their mechanisms remain elusive. We used machine learning to guide a CRISPR screening on hubs (i.e. non-coding loci forming many 3D contacts) and significantly increased the discovery rate of hubs essential for cell growth. We found no clear genetic or epigenetic differences between essential and nonessential hubs, but we observed that some neighboring hubs in the linear genome have distinct spatial contacts and opposite effects on cell growth. One such pair in an epigenetically quiescent region showed different impacts on gene expression, chromatin accessibility and chromatin organization. We also found that deleting the essential hub altered the genetic network activity and increased the entropy of chromatin accessibility, more severe than that caused by deletion of the nonessential hub, suggesting that they are critical for maintaining an ordered chromatin structure. Our study reveals new insights into the system-level roles of non-coding regions in the human genome.

Identifying unstable CNG repeat loci in the human genome: a heuristic approach and implications for neurological disorders

Tandem nucleotide repeat (TNR) expansions, particularly the CNG nucleotide configuration, are associated with a variety of neurodegenerative disorders. In this study, we aimed to identify novel unstable CNG repeat loci associated with the neurogenetic disorder spinocerebellar ataxia (SCA). Using a computational approach, 15,069 CNG repeat loci in the coding and noncoding regions of the human genome were identified. Based on the feature selection criteria (repeat length >10 and functional location of repeats), we selected 52 repeats for further analysis and evaluated the repeat length variability in 100 control subjects. A subset of 19 CNG loci observed to be highly variable in control subjects was selected for subsequent analysis in 100 individuals with SCA. The genes with these highly variable repeats also exhibited higher gene expression levels in the brain according to the tissue expression dataset (GTEx). No pathogenic expansion events were identified in patient samples, which is a limitation given the size of the patient group examined; however, these loci contain potential risk alleles for expandability. Recent studies have implicated GLS, RAI1, GIPC1, MED15, EP400, MEF2A, and CNKSR2 in neurological diseases, with GLS, GIPC1, MED15, RAI1, and MEF2A sharing the same repeat loci reported in this study. This finding validates the approach of evaluating repeat loci in different populations and their possible implications for human pathologies.

Medicinal Chemistry of Antisense Oligonucleotides for Therapeutic Use in SARS-CoV-2: Design Strategies and Challenges for Targeted Delivery

Background: The evolution of novel Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2) strains with greater degrees of infectivity, resistance to vaccine-induced acquired immunity, and more severe morbidity have contributed to the recent spread of COVID-19. In light of this, novel therapeutic alternatives with improved effectiveness and fewer side effects have become a necessity. Despite many new or repurposed antiviral agents recommended for Coronavirus disease (COVID-19) therapy, this objective remains unfulfilled. Under these circumstances, the scientific community holds the significant responsibility to develop classes of novel therapeutic modalities to combat SARS-CoV-2 with the least harmful side effects. Objective: Antisense Oligonucleotides (ASOs) are short single-stranded oligonucleotides that allow the specific targeting of RNA, leading to its degradation. They may also prevent cellular factors or machinery from binding to the target RNA. It is possible to improve the pharmacokinetics and pharmacodynamics of ASOs by chemical modification or bioconjugation, which may provide conditions for customization of a particular clinical target. This study aimed to outline the potential use of ASOs in the treatment of COVID-19 disease, along with the use of antisense stabilization and transfer methods, as well as future challenges and limitations. Methods: We have reviewed the structure and properties of ASOs containing nucleobase, sugar, or backbone modifications, and provided an overview of the therapeutic potential, delivery challenges, and strategies of ASOs in the treatment of COVID-19. Results: The first-line therapy for COVID-19-infected individuals, as well as the development of oligonucleotide-based drugs, warrants further investigation. Chemical changes in the oligonucleotide structure can affect the biological processes. These chemical alterations may lead to enhanced potency, while changing the pharmacokinetics and pharmacodynamics. Conclusion: ASOs can be designed to target both coding and non-coding regions of the viral genome to disrupt or completely degrade the genomic RNA and thereby eliminate SARS-CoV-2. They may be very effective in areas, where vaccine distribution is challenging, and they may be helpful for future coronavirus pandemics.

Mitochondrial DNA in Fornescis: Principles, Applications, and Limitations

Forensic science involves the scientific analysis and interpretation of evidence that is used in legal proceedings to establish guilt or innocence. The use of mitochondrial DNA (mtDNA) in forensics is crucial as it has several advantages over other types of DNA. For instance, mtDNA is more resistant to degradation than nuclear DNA, making it suitable for analysis even in small or degraded samples. Additionally, mtDNA is maternally inherited, and this makes it useful in tracing an individual's maternal lineage or identifying relationships between individuals across multiple generations. Another advantage of mtDNA analysis is its reliability and accuracy since it is less prone to errors or contamination. This is because mtDNA is found in the mitochondria, which are separate from the cell nucleus and are less likely to be affected by extraneous DNAor contamination. Overall, the use of mtDNA in forensic science has significantly improved the accuracy and reliability of criminal investigations, making it a vital tool in the criminal justice system. In mitochondrial DNA (mtDNA) analysis, the two regions of the mtDNA genome that are typically analyzed are hyper variable regions 1 and 2 (HV1 and HV2). HV1 and HV2 are non-coding regions of the mtDNA genome, meaning that they do not contain information for the production of proteins. Instead, they contain a high degree of variation in their nucleotide sequences, which makes them useful for identifying individuals and their maternal lineages. The interpretation of mtDNA analysis results from HV1 and HV2 involves comparing the nucleotide sequences obtained from the evidence sample to a reference database of mtDNA sequences. This comparison is done to identify any matches or differences between the sample and the reference sequences. If there are no differences or only a few, the sample is considered to be a match to the reference sequence. The more differences there are between the sample and the reference sequences, the less likely it is that the sample and reference sequences came from the same individual or maternal lineage.The interpretation of mtDNA analysis results from HV1 and HV2 can be used to provide information about the identity and maternal lineage of an individual. For example, if an evidence sample matches a reference sequence from a known maternal relative, this can be used to support the identification of the individual,

Mutational signatures of colorectal cancers according to distinct computational workflows.

Tumor mutational signatures have gained prominence in cancer research, yet the lack of standardized methods hinders reproducibility and robustness. Leveraging colorectal cancer (CRC) as a model, we explored the influence of computational parameters on mutational signature analyses across 230 CRC cell lines and 152 CRC patients. Results were validated in three independent datasets: 483 endometrial cancer patients stratified by mismatch repair (MMR) status, 35 lung cancer patients by smoking status and 12 patient-derived organoids (PDOs) annotated for colibactin exposure. Assessing various bioinformatic tools, reference datasets and input data sizes including whole genome sequencing, whole exome sequencing and a pan-cancer gene panel, we demonstrated significant variability in the results. We report that the use of distinct algorithms and references led to statistically different results, highlighting how arbitrary choices may induce variability in the mutational signature contributions. Furthermore, we found a differential contribution of mutational signatures between coding and intergenic regions and defined the minimum number of somatic variants required for reliable mutational signature assignment. To facilitate the identification of the most suitable workflows, we developed Comparative Mutational Signature analysis on Coding and Extragenic Regions (CoMSCER), a bioinformatic tool which allows researchers to easily perform comparative mutational signature analysis by coupling the results from several tools and public reference datasets and to assess mutational signature contributions in coding and non-coding genomic regions. In conclusion, our study provides a comparative framework to elucidate the impact of distinct computational workflows on mutational signatures.

Abstract A013: Functional and clinical consequences of hotspot non-coding mutations upstream of the LEPROTL1 gene in bladder cancer

Abstract Recent whole-genome sequencing studies have unveiled intriguing hotspot mutations within non-coding genomic regions, yet their implications in cancer remain unknown. Here, we characterized the role of twin hotspot non-coding mutations upstream of the LEPROTL1 gene in bladder cancer: chr8: 29,952,919 G&amp;gt;A and chr8: 29,952,919 C&amp;gt;T. Either mutation is found in ~20% of bladder tumors, and the mutations do not typically co-occur. Through a comprehensive analysis integrating ChiP-seq, ATAC-seq, and Hi-C data from bladder cancer cell lines, we observed that these mutations co-localize with enhancer elements that interact with multiple nearby genes. In vitro dual luciferase reporter assays showed that both mutations are functional and likely affect gene expression in a genomic context. CRISPR-Cas9-mediated knocking out of the putative enhancer region identified LEPROTL1, DCTN6, and SARAF as target genes that are likely co-regulated, which was further supported by strong positive correlations of their mRNA expression in TCGA data. Isogenic cell clones generated by CRISPR-mediated base-editing showed that the mutations result in simultaneous upregulation of the three target genes, which were also expressed at higher levels in TCGA tumors harboring the non-coding mutations. Little is known about the function of LEPROTL1, DCTN6, and SARAF. Utilizing siRNA knockdown models complemented by live-cell imaging, viability assays, and cell cycle analysis, we found that they promote cell proliferation and cell cycle progression. Furthermore, our base-edited isogenic cell lines showed more rapid proliferation and cell cycle progression, as well as resistance to cisplatin. The mutations were also associated with shorter disease-specific survival in a TCGA cohort, and DCTN6 showed a negative association with overall survival. These results underscore the clinical significance of the non-coding mutations. Currently, we are assessing the effect of these mutations on tumor growth and cisplatin response in vivo using xenograft mouse models and evaluating the mechanisms by which LEPROTL1, DCTN6, and SARAF modulate cell cycle progression. Taken together, our data suggest that non-coding enhancer mutations near LEPROTL1 contribute to bladder carcinogenesis by increasing the expression of three co-regulated novel oncogenes, all of which were previously uncharacterized in bladder cancer. Since we found the mutations to be clinically significant, our study also raises the possibility of using the non-coding mutations and their target genes as clinical biomarkers and potential therapeutic drug targets. Citation Format: Kelly Butler, Bilal Lone, Alexandra Dobbins, Arup Chakraborty, Salah Boudajadi, Andrea Apolo, Rouf Banday. Functional and clinical consequences of hotspot non-coding mutations upstream of the LEPROTL1 gene in bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr A013.

Abstract PR009: Exploring the functional consequences of APOBEC3-induced non-coding hotspot mutations in bladder cancer using massively parallel reporter assays and CRISPR-mediated base editing

Abstract Cancer research has traditionally focused on protein-coding genes, but approximately 98% of the human genome is non-coding, comprising gene regulatory elements such as enhancers, silencers, and promoters. Mutations within these regions can foster tumorigenesis by modulating the expression of oncogenes. Recent whole-genome sequencing studies have revealed several recurrently mutated non-coding genomic regions, including in bladder cancer, but their role in tumorigenesis remains unknown. In this study, we delved into whole-genome sequencing data from the bladder cancer TCGA cohort and an independent set of bladder tumors, uncovering hundreds of recurrent mutations. Mutational signature analysis identified over 65% of these mutations as APOBEC3-induced. We substantiated the involvement of APOBEC3 enzymes by using conventional deamination assays and novel approach dubbed as APOBEC3-mediated mutation capture assay. Predominantly, these mutations occurred in the hairpin loop, a favored motif for APOBEC3 enzymes. To systematically assess which of the mutations are functional and prioritize them for biological characterization, we developed Massively Parallel Reporter Assays (MPRA). Two types of MPRA libraries were constructed, one for evaluating promoter activity and the other for assessing enhancer activity of the mutations. Each library construction entailed 36,000 oligonucleotides, comprehensively representing all mutation hotspots and their corresponding wild-type alleles. The application of MPRA resulted in the identification of a substantial number of functionally relevant mutations. Zooming in on the top 20 genomic regions, we employed CRISPR-based approaches to pinpoint target genes and elucidate their functional consequences. Most of these regions co-localized with enhancers, as determined by analysis of ATAC-seq, ChIP-seq, and Hi-C data from bladder cancer cell lines. Perturbation of hotspots regions resulted in dysregulation of multiple genes. The co-regulation patterns of genes were further supported by strong correlation of their mRNA expression in RNA-seq datasets (TCGA, SRA, etc.). Notable examples included twin hotspot mutations upstream of the LEPROTL1 gene, elevating the expression of LEPROTL1, DCTN6 and SARAF, resulting in aggressive tumor growth in in vitro functional experiments. These three genes emerged as novel oncogenes in cancer. Another functional hotspot influenced the expression of two known long non-coding RNAs, NEAT1 and MALAT1, previously characterized as cancer genes. Additionally, some recurrently mutated regions or their target genes were associated with worse overall survival in the TCGA cohort. In conclusion, our findings propose that non-coding mutations likely drive tumorigenesis, contributing to tumor heterogeneity. Employing a combination of functional, multi-omics, and in vivo approaches, we aim to comprehensively characterize the role of hotspot non-coding mutations in bladder cancer and assess their clinical significance. Citation Format: Rouf Banday, Bilal Lone, Kelly Butler, Dhanusha Yesudhas, Alexandra Dobbins, Arup Chakraborty. Exploring the functional consequences of APOBEC3-induced non-coding hotspot mutations in bladder cancer using massively parallel reporter assays and CRISPR-mediated base editing [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr PR009.

Peripheral Blood Gene Expression Profiling Reveals Molecular Pathways Associated with Cervical Artery Dissection.

Cervical artery dissection (CeAD) is the primary cause of ischemic stroke in young adults. Monogenic heritable connective tissue diseases account for fewer than 5% of cases of CeAD. The remaining sporadic cases have known risk factors. The clinical, radiological, and histological characteristics of systemic vasculopathy and undifferentiated connective tissue dysplasia are present in up to 70% of individuals with sporadic CeAD. Genome-wide association studies identified CeAD-associated genetic variants in the non-coding genomic regions that may impact the gene transcription and RNA processing. However, global gene expression profile analysis has not yet been carried out for CeAD patients. We conducted bulk RNA sequencing and differential gene expression analysis to investigate the expression profile of protein-coding genes in the peripheral blood of 19 CeAD patients and 18 healthy volunteers. This was followed by functional annotation, heatmap clustering, reports on gene-disease associations and protein-protein interactions, as well as gene set enrichment analysis. We found potential correlations between CeAD and the dysregulation of genes linked to nucleolar stress, senescence-associated secretory phenotype, mitochondrial malfunction, and epithelial-mesenchymal plasticity.