Early onset of pathological polyploidization and cellular senescence in hepatocytes lacking RAD51 creates a pro-fibrotic and pro-tumorigenic inflammatory microenvironment.

BACKGROUND AND AIMS: RAD51 recombinase (RAD51) is a highly conserved DNA repair protein and is indispensable for embryonic viability. As a result, the role of RAD51 in liver development and function is unknown. Our aim was to characterize the function of RAD51 in postnatal liver development. APPROACH AND RESULTS: RAD51 is highly expressed during liver development and during regeneration following hepatectomy and hepatic injury, and is also elevated in chronic liver diseases. We generated a hepatocyte-specific Rad51 deletion mouse model using Alb -Cre ( Rad51 -conditional knockout (CKO)) and Adeno-associated virus 8-thyroxine-binding globulin-cyclization recombination enzyme to evaluate the function of RAD51 in liver development and regeneration. The phenotype in Rad51 -CKO mice is dependent on CRE dosage, with Rad51fl/fl ; Alb -Cre +/+ manifesting a more severe phenotype than the Rad51fl/fl ; Alb -Cre +/- mice. RAD51 deletion in postnatal hepatocytes results in aborted mitosis and early onset of pathological polyploidization that is associated with oxidative stress and cellular senescence. Remarkable liver fibrosis occurs spontaneously as early as in 3-month-old Rad51fl/fl ; Alb -Cre +/+ mice. While liver regeneration is compromised in Rad51 -CKO mice, they are more tolerant of carbon tetrachloride-induced hepatic injury and resistant to diethylnitrosamine/carbon tetrachloride-induced HCC. A chronic inflammatory microenvironment created by the senescent hepatocytes appears to activate ductular reaction the transdifferentiation of cholangiocytes to hepatocytes. The newly derived RAD51 functional immature hepatocytes proliferate vigorously, acquire increased malignancy, and eventually give rise to HCC. CONCLUSIONS: Our results demonstrate a novel function of RAD51 in liver development, homeostasis, and tumorigenesis. The Rad51 -CKO mice represent a unique genetic model for premature liver senescence, fibrosis, and hepatocellular carcinogenesis.

SPIDR is required for homologous recombination during mammalian meiosis.

Meiotic recombinases RAD51 and DMC1 mediate strand exchange in the repair of DNA double-strand breaks (DSBs) by homologous recombination. This is a landmark event of meiosis that ensures genetic diversity in sexually reproducing organisms. However, the regulatory mechanism of DMC1/RAD51-ssDNA nucleoprotein filaments during homologous recombination in mammals has remained largely elusive. Here, we show that SPIDR (scaffold protein involved in DNA repair) regulates the assembly or stability of RAD51/DMC1 on ssDNA. Knockout of Spidr in male mice causes complete meiotic arrest, accompanied by defects in synapsis and crossover formation, which leads to male infertility. In females, loss of Spidr leads to subfertility; some Spidr-/- oocytes are able to complete meiosis. Notably, fertility is rescued partially by ablation of the DNA damage checkpoint kinase CHK2 in Spidr-/- females but not in males. Thus, our study identifies SPIDR as an essential meiotic recombination factor in homologous recombination in mammals.

Rad50 promotes ovarian cancer progression through NF-κB activation.

Rad50 is a component of MRN (Mre11-Rad50-Nbs1), which participates in DNA double-strand break repair and DNA-damage checkpoint activation. Here, we sought to investigate the clinical and functional significance of Rad50 in high-grade serous ovarian cancer (HGSOC). We found that Rad50 was frequently upregulated in HGSOCs and enhanced Rad50 expression inversely correlated with patient survival. In addition, ectopic expression of Rad50 promoted proliferation/invasion and induced EMT of ovarian cancer cells, whereas knockdown of Rad50 led to decreased aggressive behaviors. Mechanistic investigations revealed that Rad50 induced aggressiveness in HGSOC via activation of NF-κB signaling pathway. Moreover, we identified CARD9 as an interacting protein of Rad50 in ovarian cancer cells and the activation of NF-κB pathway by Rad50 is CARD9 dependent. Our findings provide evidence that Rad50 exhibits oncogenic property via NF-κB activation in HGSOC.

Cyclin F and KIF20A, FOXM1 target genes, increase proliferation and invasion of ovarian cancer cells.

Increased expression of FOXM1 is observed in a variety of human malignancies. The downstream target genes of FOXM1 involved in tumorigenesis and development are not fully elucidated in ovarian cancer. Here, we identified Cyclin F, a substrate recognition subunit of SCF (Skp1-Cul1-F-box protein) complex, and Kinesin Family Member 20A (KIF20A) were transcriptionally regulated by FOXM1 in ovarian cancer. Accordingly, Cyclin F and KIF20A were commonly overexpressed in ovarian cancer. Functionally, forced expression of Cyclin F or KIF20A significantly enhanced while knockdown of them decreased proliferation and invasion of ovarian cancer cells. Importantly, high levels of Cyclin F and KIF20A correlated with poor prognosis in patients with ovarian cancer. Our findings indicate that Cyclin F and KIF20A are functional targets of FOXM1 which might be potential drug targets in ovarian cancer.

PCNA-associated factor P15PAF , targeted by FOXM1, predicts poor prognosis in high-grade serous ovarian cancer patients.

Activation of the FOXM1 signaling pathway and the PI3K/AKT/mTOR signaling pathway is associated with poor prognosis in ovarian cancer. In this study, we demonstrated that P15PAF (KIAA0101) was significantly upregulated in high-grade serous ovarian cancer (HGSOC) and that high KIAA0101 expression was associated with poor prognosis. FOXM1 transcriptionally activated KIAA0101 to drive proliferation and metastasis of ovarian cancer cells. KIAA0101 activated the PI3K/AKT/mTOR signaling pathway to inhibit cisplatin-induced apoptosis and autophagy in ovarian cancer cells resulting in cisplatin resistance. Thus, KIAA0101 was closely related to the FOXM1 and PI3K/AKT/mTOR signaling pathways. Collectively, these findings provide insights into the mechanisms of poor prognosis of ovarian cancer and have implications for the development of both predictive and therapeutic biomarkers for the treatment of ovarian cancer.

Spliceosome-associated factor CTNNBL1 promotes proliferation and invasion in ovarian cancer.

Ovarian cancer is the most lethal gynecologic malignancy and the molecular pathogenesis of high-grade serous ovarian carcinoma has not been completely characterized. Numerous studies have shown that altered splicing patterns and splicing factors were found to contribute to tumor development and progression. In this study, we demonstrated that spliceosome-associated factor CTNNBL1 was significantly upregulated in high-grade serous ovarian carcinoma, the elevated level of CTNNBL1 indicates poor prognosis in patients with high-grade serous ovarian carcinoma. Functional characterization revealed that CTNNBL1 promoted the proliferation and invasion of ovarian cancer cells in vitro. Furthermore, through transcriptome analysis, we found CTNNBL1 regulates multiple splicing events and gene expression in ovarian cancer cells. Importantly, we identified IFI16 and FOXM1 splicing was regulated by CTNNBL1. To our knowledge, this is the first study exploring the expression, functional roles and regulated splicing events of CTNNBL1 in ovarian cancer.

miR-155 Deficiency Ameliorates Autoimmune Inflammation of Systemic Lupus Erythematosus by Targeting S1pr1 in Faslpr/lpr Mice.

MicroRNA-155 (miR-155) was previously found involved in the development of systemic lupus erythematosus (SLE) and other autoimmune diseases and the inflammatory response; however, the detailed mechanism of miR-155 in SLE is not fully understood. To explore the in vivo role of miR-155 in the pathogenesis of SLE, miR-155-deficient Fas(lpr/lpr) (miR-155(-/-)Fas(lpr/lpr)) mice were obtained by crossing miR-155(-/-) and Fas(lpr/lpr) mice. Clinical SLE features such as glomerulonephritis, autoantibody levels, and immune system cell populations were compared between miR-155(-/-)Fas(lpr/lpr) and Fas(lpr/lpr) mice. Microarray analysis, RT-PCR, Western blot, and luciferase reporter gene assay were used to identify the target gene of miR-155. miR-155(-/-)Fas(lpr/lpr) mice showed milder SLE clinical features than did Fas(lpr/lpr)mice. As compared with Fas(lpr/lpr) mice, miR-155(-/-)Fas(lpr/lpr) mice showed less deposition of total IgA, IgM, and IgG and less infiltration of inflammatory cells in the kidney. Moreover, the serum levels of IL-4 and IL-17a, secreted by Th2 and Th17 cells, were lower in miR-155(-/-)Fas(lpr/lpr) than Fas(lpr/lpr) mice; the CD4(+)/CD8(+) T cell ratio was restored in miR-155(-/-)Fas(lpr/lpr) mice as well. Sphingosine-1-phosphate receptor 1 (S1PR1) was found as a new target gene of miR-155 by in vitro and in vivo studies; its expression was decreased in SLE patients and Fas(lpr/lpr) mice. miR-155(-/-)Fas(lpr/lpr) mice are resistant to the development of SLE by the regulation of the target gene S1pr1. miR-155 might be a new target for therapeutic intervention in SLE.

Synchrotron FTIR microspectroscopy reveals early adipogenic differentiation of human mesenchymal stem cells at single-cell level.

Human mesenchymal stem cells (hMSCs) have been used as an ideal in vitro model to study human adipogenesis. However, little knowledge of the early stage differentiation greatly hinders our understanding on the mechanism of the adipogenesis processes. In this study, synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopy was applied to track the global structural and compositional changes of lipids, proteins and nucleic acids inside individual hMSCs along the time course. The multivariate analysis of the SR-FTIR spectra distinguished the dynamic and significant changes of the lipids and nucleic acid at early differentiation stage. Importantly, changes of lipid structure during early days (Day 1-3) of differentiation might serve as a potential biomarker in identifying the state in early differentiation at single cell level. These results proved that SR-FTIR is a powerful tool to study the stem cell fate determination and early lipogenesis events.

Neferine induces autophagy of human ovarian cancer cells via p38 MAPK/ JNK activation.

Ovarian cancer is the most lethal gynecological malignancy. Patients usually have poor prognosis because of late diagnosis, relapse, and chemoresistance. It is pressing to seek novel agent for the treatment of ovarian cancer. Neferine is a bisbenzylisoquinoline alkaloid isolated from the embryos of lotus (Nelumbo nucifera). In this study, we investigated the antitumor effect of neferine on ovarian cancer cells. We found that neferine exhibited growth-inhibitory effect on human ovarian cancer cells, whereas showing less cytotoxic to non-malignant fallopian tube epithelial cells. Furthermore, we demonstrated that neferine induced autophagy and inactivated the mTOR pathway. Finally, we found that both p38 MAPK and JNK signaling pathways were activated by neferine treatment and contributed to the induction of autophagy in ovarian cancer cells. In conclusion, our findings showed that neferine induced autophagy of human ovarian cancer cells via p38 MAPK/JNK activation. Neferine may be explored as a promising antitumoral agent in ovarian cancer.

CUL4B activates Wnt/ß-catenin signalling in hepatocellular carcinoma by repressing Wnt antagonists.

Activation of Wnt/ß-catenin signalling is frequently observed in many types of cancer including hepatocellular carcinoma (HCC). We recently reported that cullin 4B (CUL4B), a scaffold protein that assembles CRL4B ubiquitin ligase complexes, is overexpressed in many types of solid tumours and contributes to epigenetic silencing of tumour suppressors. In this study, we characterized the function of CUL4B in HCC and investigated whether CUL4B is involved in the regulation of Wnt/ß-catenin signalling. CUL4B and ß-catenin were frequently up-regulated and positively correlated in HCC tissues. CUL4B activated Wnt/ß-catenin signalling by protecting ß-catenin from GSK3-mediated degradation, achieved through CUL4B-mediated epigenetic silencing of Wnt pathway antagonists. Knockdown of CUL4B resulted in the up-regulation of Wnt signal antagonists such as DKK1 and PPP2R2B. Simultaneous knockdown of PPP2R2B partially reversed the down-regulation of ß-catenin signalling caused by CUL4B depletion. Furthermore, CRL4B promoted the recruitment and/or retention of PRC2 at the promoters of Wnt antagonists and CUL4B knockdown decreased the retention of PRC2 components as well as H3K27me3. Knockdown of CUL4B reduced the proliferation, colony formation, and invasiveness of HCC cells in vitro and inhibited tumour growth in vivo, and these effects were attenuated by introduction of exogenous ß-catenin or simultaneous knockdown of PPP2R2B. Conversely, ectopic expression of CUL4B enhanced the proliferation and invasiveness of HCC cells. We conclude that CUL4B can up-regulate Wnt/ß-catenin signalling in human HCC through transcriptionally repressing Wnt antagonists and thus contributes to the malignancy of HCC.

MDC1 promotes ovarian cancer metastasis by inducing epithelial-mesenchymal transition.

Ovarian cancer is a highly invasive cancer with poor prognosis. Previous studies have revealed lots of connections between the invasiveness and epithelial-mesenchymal transition (EMT), which is common during the progression of ovarian cancer. MDC1, a mediator of DNA damage checkpoint, has recently been implicated as a potential oncogene. Here, in this article, we studied the role of MDC1 in ovarian cancer metastasis. First, in tissue samples, we found that high expression level of MDC1 was correlated with poor prognosis. Furthermore, MDC1 overexpression in ovarian cancer cells significantly increased migration and invasion. In contrast, silencing MDC1 reversed these processes. Consistently, nude mice xenograft confirmed that silencing MDC1 suppressed tumor metastasis in vivo. We further demonstrated that MDC1 induced EMT through modulation EMT markers such as E-cadherin, N-cadherin, and vimentin. Taken together, our findings suggest that MDC1 promotes ovarian cancer metastasis through the induction of EMT.

TMC7 deficiency causes acrosome biogenesis defects and male infertility in mice.

Transmembrane channel-like (TMC) proteins are a highly conserved ion channel family consisting of eight members (TMC1-TMC8) in mammals. TMC1/2 are components of the mechanotransduction channel in hair cells, and mutations of TMC1/2 cause deafness in humans and mice. However, the physiological roles of other TMC proteins remain largely unknown. Here, we show that Tmc7 is specifically expressed in the testis and that it is required for acrosome biogenesis during spermatogenesis. Tmc7-/- mice exhibited abnormal sperm head, disorganized mitochondrial sheaths, and reduced number of elongating spermatids, similar to human oligo-astheno-teratozoospermia. We further demonstrate that TMC7 is colocalized with GM130 at the cis-Golgi region in round spermatids. TMC7 deficiency leads to aberrant Golgi morphology and impaired fusion of Golgi-derived vesicles to the developing acrosome. Moreover, upon loss of TMC7 intracellular ion homeostasis is impaired and ROS levels are increased, which in turn causes Golgi and endoplasmic reticulum stress. Taken together, these results suggest that TMC7 is required to maintain pH and ion homeostasis, which is needed for acrosome biogenesis. Our findings unveil a novel role for TMC7 in acrosome biogenesis during spermiogenesis.

The deubiquitinase cofactor UAF1 interacts with USP1 and plays an essential role in spermiogenesis.

Spermiogenesis defines the final phase of male germ cell differentiation. While multiple deubiquitinating enzymes have been linked to spermiogenesis, the impacts of deubiquitination on spermiogenesis remain poorly characterized. Here, we investigated the function of UAF1 in mouse spermiogenesis. We selectively deleted Uaf1 in premeiotic germ cells using the Stra8-Cre knock-in mouse strain (Uaf1 sKO), and found that Uaf1 is essential for spermiogenesis and male fertility. Further, UAF1 interacts and colocalizes with USP1 in the testes. Conditional knockout of Uaf1 in testes results in disturbed protein levels and localization of USP1, suggesting that UAF1 regulates spermiogenesis through the function of the deubiquitinating enzyme USP1. Using tandem mass tag-based proteomics, we identified that conditional knockout of Uaf1 in the testes results in reduced levels of proteins that are essential for spermiogenesis. Thus, we conclude that the UAF1/USP1 deubiquitinase complex is essential for normal spermiogenesis by regulating the levels of spermiogenesis-related proteins.

CWF19L2 is Essential for Male Fertility and Spermatogenesis by Regulating Alternative Splicing.

The progression of spermatogenesis along specific developmental trajectories depends on the coordinated regulation of pre-mRNA alternative splicing (AS) at the post-transcriptional level. However, the fundamental mechanism of AS in spermatogenesis remains to be investigated. Here, it is demonstrated that CWF19L2 plays a pivotal role in spermatogenesis and male fertility. In germline conditional Cwf19l2 knockout mice exhibiting male sterility, impaired spermatogenesis characterized by increased apoptosis and decreased differentiated spermatogonia and spermatocytes is observed. That CWF19L2 interacted with several spliceosome proteins to participate in the proper assembly and stability of the spliceosome is discovered. By integrating RNA-seq and LACE-seq data, it is further confirmed CWF19L2 directly bound and regulated the splicing of genes related to spermatogenesis (Znhit1, Btrc, and Fbxw7) and RNA splicing (Rbfox1, Celf1, and Rbm10). Additionally, CWF19L2 can indirectly amplify its effect on splicing regulation through modulating RBFOX1. Collectively, this research establishes that CWF19L2 orchestrates a splicing factor network to ensure accurate pre-mRNA splicing during the early steps of spermatogenesis.

Splicing Factor PQBP1 Curtails BAX Expression to Promote Ovarian Cancer Progression.

Splicing factor polyglutamine binding protein-1 (PQBP1) is abundantly expressed in the central nervous system during development, and mutations in the gene cause intellectual disability. However, the roles of PQBP1 in cancer progression remain largely unknown. Here, it is shown that PQBP1 overexpression promotes tumor progression and indicates worse prognosis in ovarian cancer. Integrative analysis of spyCLIP-seq and RNA-seq data reveals that PQBP1 preferentially binds to exon regions and modulates exon skipping. Mechanistically, it is shown that PQBP1 regulates the splicing of genes related to the apoptotic signaling pathway, including BAX. PQBP1 promotes BAX exon 2 skipping to generate a truncated isoform that undergoes degradation by nonsense-mediated mRNA decay, thus making cancer cells resistant to apoptosis. In contrast, PQBP1 depletion or splice-switching antisense oligonucleotides promote exon 2 inclusion and thus increase BAX expression, leading to inhibition of tumor growth. Together, the results demonstrate an oncogenic role of PQBP1 in ovarian cancer and suggest that targeting the aberrant splicing mediated by PQBP1 has therapeutic potential in cancer treatment.

Polyamine Anabolism Promotes Chemotherapy-Induced Breast Cancer Stem Cell Enrichment.

Breast cancer patients may initially benefit from cytotoxic chemotherapy but experience treatment resistance and relapse. Chemoresistant breast cancer stem cells (BCSCs) play a pivotal role in cancer recurrence and metastasis, however, identification and eradication of BCSC population in patients are challenging. Here, an mRNA-based BCSC signature is developed using machine learning strategy to evaluate cancer stemness in primary breast cancer patient samples. Using the BCSC signature, a critical role of polyamine anabolism in the regulation of chemotherapy-induced BCSC enrichment, is elucidated. Mechanistically, two key polyamine anabolic enzymes, ODC1 and SRM, are directly activated by transcription factor HIF-1 in response to chemotherapy. Genetic inhibition of HIF-1-controlled polyamine anabolism blocks chemotherapy-induced BCSC enrichment in vitro and in xenograft mice. A novel specific HIF-1 inhibitor britannin is identified through a natural compound library screening, and demonstrate that coadministration of britannin efficiently inhibits chemotherapy-induced HIF-1 transcriptional activity, ODC1 and SRM expression, polyamine levels, and BCSC enrichment in vitro and in xenograft and autochthonous mouse models. The findings demonstrate the key role of polyamine anabolism in BCSC regulation and provide a new strategy for breast cancer treatment.

MiR-182 overexpression in tumourigenesis of high-grade serous ovarian carcinoma.

Molecular pathogenesis of high-grade serous ovarian carcinoma (HG-SOC) is poorly understood. Recent recognition of HG-SOC precursor lesions, defined as serous tubal intraepithelial carcinoma (STIC) in fimbria, provides a new venue for the study of early genetic changes in HG-SOC. Using microRNA profiling analysis, we found that miR-182 expression was significantly higher in STIC than in matched normal Fallopian tube. Further study revealed that miR-182 was significantly overexpressed in most HG-SOC cases. To test whether miR-182 plays a major role in early tumourigenesis of HG-SOC, we overexpressed miR-182 in immortalized ovarian surface, Fallopian tube secretory cells and malignant ovarian cell lines, and found that miR-182 overexpression resulted in increased tumour transformation in vitro, and enhanced tumour invasiveness in vitro and metastasis in vivo. Mechanistically, we demonstrated that the oncogenic properties of miR-182 in ovarian cancer were mediated in part by its impaired repair of DNA double-strand breaks and negative regulation of breast cancer 1 (BRCA1) and metastasis suppressor 1 (MTSS1) expression as well as its positive regulation of the oncogene high-mobility group AT-hook 2 (HMGA2). Our findings suggest that miR-182 dysregulation confers powerful oncogenic potential in the tumourigenesis of HG-SOC. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Spliceosome component Usp39 contributes to hepatic lipid homeostasis through the regulation of autophagy.

Regulation of alternative splicing (AS) enables a single transcript to yield multiple isoforms that increase transcriptome and proteome diversity. Here, we report that spliceosome component Usp39 plays a role in the regulation of hepatocyte lipid homeostasis. We demonstrate that Usp39 expression is downregulated in hepatic tissues of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) subjects. Hepatocyte-specific Usp39 deletion in mice leads to increased lipid accumulation, spontaneous steatosis and impaired autophagy. Combined analysis of RNA immunoprecipitation (RIP-seq) and bulk RNA sequencing (RNA-seq) data reveals that Usp39 regulates AS of several autophagy-related genes. In particular, deletion of Usp39 results in alternative 5' splice site selection of exon 6 in Heat shock transcription factor 1 (Hsf1) and consequently its reduced expression. Importantly, overexpression of Hsf1 could attenuate lipid accumulation caused by Usp39 deficiency. Taken together, our findings indicate that Usp39-mediated AS is required for sustaining autophagy and lipid homeostasis in the liver.

Bud31-mediated alternative splicing is required for spermatogonial stem cell self-renewal and differentiation.

Alternative splicing (AS) is tightly regulated during cell differentiation and development. AS events are prevalent in the testis, but the splicing regulation in spermatogenesis remains unclear. Here we report that the spliceosome component Bud31 plays a crucial role during spermatogenesis in mice. Germ cell-specific knockout of Bud31 led to loss of spermatogonia and to male infertility. We further demonstrate that Bud31 is required for both spermatogonial stem cell pool maintenance and the initiation of spermatogenesis. SMART-seq revealed that deletion of Bud31 in germ cells causes widespread exon-skipping and intron retention. Particularly, we identified Cdk2 as one of the direct splicing targets of Bud31, knockout of Bud31 resulted in retention of the first intron of Cdk2, which led to a decrease in Cdk2 expression. Our findings suggest that Bud31-mediated AS within spermatogonial stem cells regulates the self-renewal and differentiation of male germ cells in mammals.

MYC reshapes CTCF-mediated chromatin architecture in prostate cancer.

MYC is a well characterized oncogenic transcription factor in prostate cancer, and CTCF is the main architectural protein of three-dimensional genome organization. However, the functional link between the two master regulators has not been reported. In this study, we find that MYC rewires prostate cancer chromatin architecture by interacting with CTCF protein. Through combining the H3K27ac, AR and CTCF HiChIP profiles with CRISPR deletion of a CTCF site upstream of MYC gene, we show that MYC activation leads to profound changes of CTCF-mediated chromatin looping. Mechanistically, MYC colocalizes with CTCF at a subset of genomic sites, and enhances CTCF occupancy at these loci. Consequently, the CTCF-mediated chromatin looping is potentiated by MYC activation, resulting in the disruption of enhancer-promoter looping at neuroendocrine lineage plasticity genes. Collectively, our findings define the function of MYC as a CTCF co-factor in three-dimensional genome organization.