Biology subjects

An, O.

Publications and source records attributed to An, O..

10 recordsLinked to original sources

bioRxiv2026

Intron 13 retention expands the ADAR1 isoform repertoire to rewire PKR signaling and promote tumorigenesis

For decades, the biology of ADAR1 has been framed around two major isoforms: the nuclear-enriched p110 and the predominantly cytoplasmic p150. Here, we reveal an unexpected repertoire expansion of ADAR1 isoforms that is driven by intron retention. Specifically, intron 13 (I13) can be retained in ADAR1 transcripts, conferred by an evolutionarily conserved weaker 5SS. In addition, we found that the I13 retention (I13R) is negatively autoregulated by ADAR1 through antagonizing the binding of hnRNPA1 to I13 in an editing-independent manner. Despite being sensitive to nonsense-mediated decay, I13R generates two previously uncharacterized truncated isoforms - p90 and p130, that both lack the C-terminal portion of the deaminase domain. Intriguingly, ADAR1p90 - a derivative of the canonical nuclear-enriched p110 isoform - is predominantly cytoplasmic, that effectively represses PKR and eIF2 activation through the sequestration of immunogenic double-stranded RNA (dsRNA) substrates. Furthermore, in a colorectal cancer (CRC) cohort, p90 levels are increased in most tumors relative to matched normal tissues that positively correlates with hnRNPA1 expression. Functionally, xenografts expressing ADAR1p90 grow significantly faster and larger than those expressing ADAR1p110, indicating enhanced tumorigenic potential. These findings revise the canonical view of ADAR1 isoforms, demonstrating that intron retention can generate alternative isoforms with augmented functions that tumors readily exploit. One Sentence SummaryThe conserved retention of I13 in ADAR1 transcripts gives rise to previously uncharacterized C-terminal truncated cytoplasmic ADAR1 isoforms, p90 and p130, which, although devoid of catalytic activity, sequester immunogenic dsRNA substrates, thereby preventing PKR binding and downstream activation of eIF2.

cell biology↗

bioRxiv2022

FEZ1 participates in human embryonic brain development by modulating neuronal progenitor subpopulation specification and migration

Abnormal neuronal networks arising from perturbations during early brain development contribute to neurodevelopmental disorders. Mutations and deletions of human Fasciculation and Elongation Protein Zeta 1 (FEZ1) are found in schizophrenia and Jacobsen syndrome patients. However, its roles in human brain development and manifestation of clinical pathological symptoms remain unknown. Here, using human cerebral organoids (hCOs), we observed that FEZ1 expression is turned on early during brain development and is detectable in both neuroprogenitor subtypes and immature neurons. Deletion of FEZ1 disrupts expression of genes involved in neuronal and synaptic development. Using single-cell RNA sequencing, we further uncovered an abnormal expansion of homeodomain-only protein homeobox (HOPX)- outer radial glia (oRG) in FEZ1-null hCOs, occurring at the expense of HOPX+ oRG. HOPX- oRGs show higher cell mobility as compared to HOPX+ oRGs, which is accompanied by the ectopic localization of the neuroprogenitors to the outer layer of FEZ1-null hCOs. Moreover, abnormal encroachment of TBR2+ intermediate progenitors into CTIP2+ deep layer neurons indicated that cortical layer formation is disrupted in FEZ1-null hCOs. Collectively, our findings highlight the involvement of FEZ1 in early cortical brain development and how it contributes to neurodevelopmental disorders.

neuroscience↗

bioRxiv2022

Exploring the Neoantigen burden in Breast Carcinoma Patients

In this study we performed a multi-omics analysis comprising whole-exome sequencing (WES) and RNA sequencing (RNA-Seq) on seven breast cancer patients, consisting of three Estrogen receptor (ER) positive and four Triple negative breast cancer (TNBC) subtypes to understand the neoantigen burden in breast cancer tumor samples. We predicted both class-I and class-II human leukocyte antigen (HLA) bound neoantigens by analyzing matched tumor-normal pair of exomes. Across all the patients, we predicted 434 unique neoantigens (NeoFil) in total, affecting 237 different genes and 87% of them (n = 378) are expressed at RNA level (Neoexp). The missense mutations (87%) are the major contributor in neoantigen (Neoexp) generation, followed by frameshift (11%) and indels (2%). The neoantigens (NeoFil) were found to be positively correlated with the somatic mutations (R2 = 0.89). We also noted that the vast majority (99.98%) of the predicted neoantigens are patient specific. Overall, the current study offers significant insight into the neoantigen profile in tumor types with intermediate/low mutation burdens like breast cancer.

cancer biology↗

bioRxiv2021

ADAR2-repressed RNA editing: a novel mechanism contributing to t (8:21) AML leukemogenesis

In the past decade, adenosine to inosine (A-to-I) RNA editing, which is catalyzed by adenosine deaminases acting on RNA (ADAR) family of enzymes ADAR1 and ADAR2, has been shown to contribute to the development and progression of multiple cancers; however, very little is known about its role in acute myeloid leukemia (AML) - the second most common type of leukemia making up 31% of all adult leukemia cases. Here, we found that ADAR2, but not ADAR1 and ADAR3, is specifically downregulated in core binding factor (CBF) AML with t(8;21) or inv(16). In t(8;21) AML, RUNX1-driven transcription of ADAR2 transcripts was found to be repressed by the RUNX1-ETO fusion protein. Forced overexpression of two ADAR2-regulated RNA editing targets COPA and COG3 indeed inhibits clonogenic growth of human t(8;21) AML cells. Further in vivo animal studies confirmed that ADAR2 could suppress leukemogenesis of t(8;21) AML through its RNA binding and editing capabilities. Our results suggest a novel RNA editing-mediated mechanism leading to t(8,12) AML. Key pointsO_LIADAR2, but not ADAR1 and ADAR3, was specifically downregulated in CBF-AML C_LIO_LIRUNX1-ETO suppresses ADAR2 transcription in t(8;21) AML through binding on its promoter C_LIO_LIRNA editing capability of ADAR2 is essential for its repression of leukemogenesis in an AE9a mouse model C_LI

cancer biology↗

bioRxiv2021

PLK1 inhibition selectively kills ARID1A deficient cells through uncoupling of oxygen consumption from ATP production

Inhibitors of the mitotic kinase PLK1 yield objective responses in a subset of refractory cancers. However, PLK1 overexpression in cancer does not correlate with drug sensitivity, and the clinical development of PLK1 inhibitors has been hampered by the lack of patient selection marker. Using a high-throughput chemical screen, we discovered that cells deficient for the tumor suppressor ARID1A are highly sensitive to PLK1 inhibition. Interestingly this sensitivity was unrelated to canonical functions of PLK1 in mediating G2-M cell cycle transition. Instead, a whole-genome CRISPR screen revealed PLK1 inhibitor sensitivity in ARID1A deficient cells to be dependent on the mitochondrial translation machinery. We find that ARID1A knocked-out (KO) cells have an unusual mitochondrial phenotype with aberrant biogenesis, increased oxygen consumption/ expression of oxidative phosphorylation genes, but without increased ATP production. Using expansion microscopy and biochemical fractionation, we see that a subset of PLK1 localizes to the mitochondria in interphase cells. Inhibition of PLK1 in ARID1A KO cells further uncouples oxygen consumption from ATP production, with subsequent membrane depolarization and apoptosis. Knockdown of a key subunit of the mitochondrial ribosome reverses PLK1-inhibitor induced apoptosis in ARID1A deficient cells, confirming specificity of the phenotype. Together, these findings highlight a novel interphase role for PLK1 in maintaining mitochondrial fitness under metabolic stress, and a strategy for therapeutic use of PLK1 inhibitors. To translate these findings, we describe a quantitative microscopy assay for assessment of ARID1A protein loss, which could offer a novel patient selection strategy for the clinical development of PLK1 inhibitors in cancer. Statement of significanceCurrently, no predictive biomarkers have been identified for PLK1 inhibitors in cancer treatment. We show that ARID1A loss sensitizes cells to PLK1 inhibitors through a previously unrecognized vulnerability in mitochondrial oxygen metabolism.

cancer biology↗

bioRxiv2021

Generation of human chambered cardiac organoids from pluripotent stem cells for improved modelling of cardiovascular diseases

Recent progress on murine and human cardiac organoids have provided understanding to the developmental processes of the heart. However, there is still an unfulfilled need for improved modelling of cardiovascular diseases using human cardiac organoids. Herein, we report successful generation of intrinsically formed human chambered cardiac organoids (CCO) and highlight its utility in modelling disease. Single cell transcriptomic profiling of CCOs showed appropriate cardiovascular cell type composition exhibiting improved maturation. Functionally, CCOs recapitulated clinical cardiac hypertrophy by exhibiting thickened chamber walls, reduced ejection fractions, increased myofibrillar disarray and tachycardia. Therefore, CCOs improve current capabilities of disease modelling as an in vitro model bridging the gap to in vivo models, with the ability to assess functional parameters that previously can only be achieved in animal systems. One sentence summaryModelling cardiac hypertrophy using chambered cardiac organoids derived from human pluripotent stem cells.

cell biology↗

bioRxiv2020

"3G" Trial: An RNA Editing Signature for Guiding Gastric Cancer Chemotherapy

Background & AimsGastric cancer (GC) cases are often diagnosed at an advanced stage with poor prognosis. Platinum-based chemotherapy has been internationally accepted as first-line therapy for inoperable or metastatic GC. To achieve greater benefits, it is critical to select patients who are eligible for the treatment. Albeit gene expression profiling has been widely used as a genomic classifier to identify molecular subtypes of GC and stratify patients for different chemotherapy regimens, the prediction accuracy remains to be improved. More recently, adenosine-to-inosine (A-to-I) RNA editing has emerged as a new player contributing to GC development and progression, offering potential clinical utility for diagnosis and treatment. MethodsWe conducted a transcriptome-wide RNA editing analysis of a cohort of 104 patients with advanced GC and identified an RNA editing (GCRE) signature to guide GC chemotherapy, using a systematic computational approach followed by both in vitro validations and in silico validations in TCGA. ResultsWe found that RNA editing events alone stand as a prognostic and predictive biomarker in advanced GC. We developed a GCRE score based on the GCRE signature consisting of 50 editing sites associated with 29 genes and achieved a high accuracy (84%) of predicting patient response to chemotherapy. Of note, patients demonstrating higher editing levels of this panel of sites present a better overall response. Consistently, GC cell lines with higher editing levels showed higher chemosensitivity. Applying the GCRE score on TCGA dataset confirmed that responders had significantly higher levels of editing in advanced GC. ConclusionsOverall, the GCRE signature reliably stratifies patients with advanced GC and predicts response from chemotherapy. SignificanceDespite the increasing documentation of RNA editing and its functional regulation, the translational potential of RNA editome in cancer remains largely under-investigated. This study reports for the first time an RNA editing signature in advanced GC, to reliably stratify patients with advanced disease to predict response from chemotherapy independently of gene expression profiling and other genomic and epigenetic changes. For this purpose, a bioinformatics approach was used to develop a GCRE score based on a panel of 50 editing sites from 29 unique genes (GCRE signature), followed by an experimental evaluation of their clinical utility as predictive biomarker in GC cell lines and in silico validation in using RNA sequencing (RNA-Seq) datasets from TCGA. The applied methodology provides a robust means of an RNA editing signature to be investigated in patients with advanced GC. Overall, this study provides insights into the translation of RNA editing process into predictive clinical applications to direct chemotherapy against GC.

cancer biology↗

bioRxiv2020

HNRNPM controls circRNA biogenesis and splicing fidelity to sustain prostate cancer cell fitness

Cancer cells are differentially dependent on the splicing machinery compared to normal untransformed cells. The splicing machinery thus represents a potential therapeutic target in cancer. To identify splicing factors important for prostate cancer cell (PCa) cell growth, we performed a parallel pooled shRNA screen on in vitro passaged cells and in vivo xenografted PCa tumor lines. Our screen revealed HNRNPM as a potential regulator of PCa cell growth. RNA- and eCLIP-sequencing data suggest that HNRNPM is bound to transcripts of key homeostatic genes and that loss of HNRNPM binding in a subset of these genes results in aberrant exon inclusion and exon back-splicing events in target transcripts. In both linear and circular mis-spliced transcripts, HNRNPM appears to preferentially bind to GU-rich elements in long flanking proximal introns. Mimicry of HNRNPM dependent linear splicing events using splice-switching antisense oligonucleotides (SSOs) was sufficient to inhibit cell growth in HNRNPM expressing cells. This suggests that prostate cancer cell dependence on HNRNPM is likely a result of mis-splicing of key homeostatic coding and non-coding genes. Taken together, our data reveal a role for HNRNPM in supporting prostate cancer cell fitness, and also as a potential therapeutic target in PCa.

genomics↗

bioRxiv2020

Three-dimensional Genome Organization Maps in Normal Haematopoietic Stem Cells and Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is a highly lethal blood cancer arising due to aberrant differentiation of haematopoietic stem cells. Here we obtained 3D genome organization maps by Hi-C in the CD34+ haematopoietic stem cells from three healthy individuals and eight individuals with AML, and found that AML have increased loops to oncogenes compared with normal CD34+ cells. The MEIS1 oncogenic transcription factor is regulated by a Frequently Interacting Region (FIRE). This FIRE is only present in normal bone marrow samples, and four of eight AML sample. FIRE presence is associated with MEIS1 expression. CRISPR excision of a FIRE boundary led to loss of MEIS1 and reduced cell growth. Moreover, MEIS1 can bind to the promoter of HOXA9, and HOXA9 shows gain of Acute Myeloid Leukemia-specific super-enhancers that loop to the HOXA9 promoter. SignificanceWe found that Acute Myeloid Leukemias have more chromatin loops to oncogenes compared with normal blood stem cells. We identified heterogeneity in chromatin interactions at oncogenes, and heterogeneity in super-enhancers that loop to oncogenes, as two key epigenetic mechanisms that underlie MEIS1 and HOXA9 oncogene expression respectively.

cancer biology↗

bioRxiv2019

Widespread interaction between ADAR1 and transcriptional byproducts

BackgroundADAR1, an adenosine-to-inosine (A-to-I) RNA editing enzyme, has an emerging role in cancer immunotherapy. ADAR1 presumably works by suppressing cellular innate immunity response to endogenously generated double-stranded RNAs through RNA editing. However, RNA species that are directly regulated by ADAR1 mediated RNA editing processes remain poorly defined. ResultsIn this study, we used a novel bioinformatics approach to track ADAR1-RNA interactions. By integrating DNA-seq, RNA-seq, and ADAR1 RNA immunoprecipitation sequencing (fRIP-seq) data of K562 cell line, we provided the first in-situ landscape profiling of ADAR1 RNA binding and editing activities. With long RNA fragments captured by ADAR1 immunoprecipitation, we were able to identify exon junctions and genomic boundaries used by ADAR1-associated RNAs and thus we could possibly trace pre-RNA processing steps that had been acting on them. Our methodology allowed us to acquire the knowledge of transcriptome-wide scenario of ADAR1 activities. Intriguingly, we found that ADAR1 had a tendency to interact with transcriptional byproducts originated from obscure regions such as introns and intergenic regions. ConclusionsOur observation might shed light on the dual role of ADAR1 proteins not only in diversifying the transcriptome, but also in reigning RNA debris from obscure regions. Moreover, as the functional potential of seemly transcriptional byproducts is just beginning to emerge, this study would bridge ADAR1 with other fields of RNA biology.

genomics↗