Silencing of CCR4-NOT complex subunits affects heart structure and function

Ubiquitination-deficit of Cnot4 impairs the capacity of proliferation and differentiation in mouse embryonic stem cells

Neurodevelopmental abnormalities are significant contributors to a variety of neurological disorders. Ubiquitination is essential for embryonic development and plays a pivotal role in neurodevelopment. Although Cnot4 possesses E3-ubiquitin ligase activity, its function in neurodevelopment and embryonic stem cells (ESCs) remains inadequately understood. This study examined the impact of Cnot4 ubiquitination-deficit in mouse ESCs using flow cytometry, CCK-8 assays, immunofluorescence, western blotting, RNA sequencing (RNA-seq), and intracellular Ca2+ measurement. Findings demonstrated that the lack of ubiquitination in Cnot4 reduced ESC proliferation rates and facilitated ectodermal differentiation during spontaneous ESC differentiation. RNA-seq analysis identified that the differentially expressed genes were primarily linked to glucose metabolism and Ca2+ signaling pathways. Additionally, results indicated that the ubiquitination-deficit in Cnot4 caused increased intracellular Ca2+ levels in mESCs. These findings suggest that Cnot4 plays a critical role in the regulation of proliferation and differentiation of mESCs through ubiquitination, providing a basis for further exploration of its involvement in embryonic and neural development.

A DNA methylation haplotype block landscape in human tissues and preimplantation embryos reveals regulatory elements defined by comethylation patterns

DNA methylation and associated regulatory elements play a crucial role in gene expression regulation. Previous studies have focused primarily on the distribution of mean methylation levels. Advances in whole-genome bisulfite sequencing (WGBS) have enabled the characterization of DNA methylation haplotypes (MHAPs), representing CpG sites from the same read fragment on a single chromosome, and the subsequent identification of methylation haplotype blocks (MHBs), in which adjacent CpGs on the same fragment are comethylated. Using our expert-curated WGBS data sets, we report comprehensive landscapes of MHBs in 17 representative normal somatic human tissues and during early human embryonic development. Integrative analysis reveals MHBs as a distinctive type of regulatory element characterized by comethylation patterns rather than mean methylation levels. We show the enrichment of MHBs in open chromatin regions, tissue-specific histone marks, and enhancers, including super-enhancers. Moreover, we find that MHBs tend to localize near tissue-specific genes and show an association with differential gene expression that is independent of mean methylation. Similar findings are observed in the context of human embryonic development, highlighting the dynamic nature of MHBs during early development. Collectively, our comprehensive MHB landscapes provide valuable insights into the tissue specificity and developmental dynamics of DNA methylation.

CNOT4 suppresses nonsmall cell lung cancer progression by promoting the degradation of PAF1

CCR4-NOT transcription complex subunit 4 (CNOT4) and RNA polymerase II-associated factor, homolog (Saccharomyces cerevisiae) (PAF1) are implicated in nonsmall cell lung cancer (NSCLC). However, the molecular mechanism of their interaction in NSCLC progression is unknown. The expression of PAF1 and CNOT4 in human NSCLC tissues was detected by quantitative polymerase chain reaction. A549 cells that stably expressed CNOT4 and/or PAF1 were established. Western blot analysis and co-immunoprecipitation experiments were performed to reveal the interaction between CNOT4 and PAF1. Proliferation, migration, epithelial-mesenchymal transition (EMT), and colony formation assays were performed to determine the effect of CNOT4-PAF1 axis on NSCLC metastasis and stemness. Xenograft mouse tumor model was established, and tumor progression, EMT, and stemness were evaluated. It was found that CNOT4 expression was downregulated, whereas PAF1 expression was upregulated in human NSCLC tissues. CNOT4 facilitated the ubiquitination and degradation of PAF1 via the 26S proteasome. CNOT4 overexpression inhibited NSCLC progression, whereas PAF1 overexpression enhanced the proliferation, migration, and stemness of NSCLC, both in vitro and in vivo. Our results suggest that CNOT4-PAF1 axis modulates NSCLC metastasis and stemness, and may serve as potential therapeutic targets for lung cancer treatment.

Multiplatform modeling of atrial fibrillation identifies phospholamban as a central regulator of cardiac rhythm

Atrial fibrillation (AF) is a common and genetically inheritable form of cardiac arrhythmia; however, it is currently not known how these genetic predispositions contribute to the initiation and/or maintenance of AF-associated phenotypes. One major barrier to progress is the lack of experimental systems to investigate the effects of gene function on rhythm parameters in models with human atrial and whole-organ relevance. Here, we assembled a multi-model platform enabling high-throughput characterization of the effects of gene function on action potential duration and rhythm parameters using human induced pluripotent stem cell-derived atrial-like cardiomyocytes and a Drosophila heart model, and validation of the findings using computational models of human adult atrial myocytes and tissue. As proof of concept, we screened 20 AF-associated genes and identified phospholamban loss of function as a top conserved hit that shortens action potential duration and increases the incidence of arrhythmia phenotypes upon stress. Mechanistically, our study reveals that phospholamban regulates rhythm homeostasis by functionally interacting with L-type Ca2+ channels and NCX. In summary, our study illustrates how a multi-model system approach paves the way for the discovery and molecular delineation of gene regulatory networks controlling atrial rhythm with application to AF.

Bidirectional roles of the Ccr4-Not complex in regulating autophagy before and after nitrogen starvation

Macroautophagy/autophagy is a highly conserved catabolic process by which cytoplasmic constituents are delivered to the vacuole/lysosome for degradation and recycling. To maintain cellular homeostasis and prevent pathologies, the induction and amplitude of autophagy activity are finely controlled through regulation of ATG gene expression. Here we report that the Ccr4-Not complex in Saccharomyces cerevisiae has bidirectional roles in regulating autophagy before and after nutrient deprivation. Under nutrient-rich conditions, Ccr4-Not directly targets the mRNAs of several ATG genes in the core autophagy machinery to promote their degradation through deadenylation, thus contributing to maintaining autophagy at the basal level. Upon starvation, Ccr4-Not releases its repression of these ATG genes and switches its role to promote the expression of a different subset of ATG genes, which is required for sufficient autophagy induction and activity. These results reveal that the Ccr4-Not complex is indispensable to maintain autophagy at the appropriate amplitude in both basal and stress conditions.Abbreviations: AID, auxin-inducible degron; Ape1, aminopeptidase I; Atg, autophagy related; Cvt, cytoplasm-to-vacuole targeting; DMSO, dimethyl sulfoxide; IAA, indole-3-acetic acid; PA, protein A; RIP, RNA immunoprecipitation.

Distinct patterns of gene expression during regeneration and asexual reproduction in the annelid Pristina leidyi

Regeneration, the ability to replace lost body parts, is a widespread phenomenon in the animal kingdom often connected to asexual reproduction or fission, since the only difference between the two appears to be the stimulus that triggers them. Both developmental processes have largely been characterized; however, the molecular toolkit and genetic mechanisms underlying these events remain poorly unexplored. Annelids, in particular the oligochaete Pristina leidyi, provide a good model system to investigate these processes as they show diverse ways to regenerate, and can reproduce asexually through fission under laboratory conditions. Here, we used a comparative transcriptomics approach based on RNA-sequencing and differential gene expression analyses to understand the molecular mechanisms involved in anterior regeneration and asexual reproduction. We found 291 genes upregulated during anterior regeneration, including several regeneration-related genes previously reported in other annelids such as frizzled, paics, and vdra. On the other hand, during asexual reproduction, 130 genes were found upregulated, and unexpectedly, many of them were related to germline development during sexual reproduction. We also found important differences between anterior regeneration and asexual reproduction, with the latter showing a gene expression profile more similar to that of control individuals. Nevertheless, we identified 35 genes that were upregulated in both conditions, many of them related to cell pluripotency, stem cells, and cell proliferation. Overall, our results shed light on the molecular mechanisms that control anterior regeneration and asexual reproduction in annelids and reveal similarities with other animals, suggesting that the genetic machinery controlling these processes is conserved across metazoans.

In vivo identification and validation of novel potential predictors for human cardiovascular diseases

Genetics crucially contributes to cardiovascular diseases (CVDs), the global leading cause of death. Since the majority of CVDs can be prevented by early intervention there is a high demand for the identification of predictive causative genes. While genome wide association studies (GWAS) correlate genes and CVDs after diagnosis and provide a valuable resource for such causative candidate genes, often preferentially those with previously known or suspected function are addressed further. To tackle the unaddressed blind spot of understudied genes, we particularly focused on the validation of human heart phenotype-associated GWAS candidates with little or no apparent connection to cardiac function. Building on the conservation of basic heart function and underlying genetics from fish to human we combined CRISPR/Cas9 genome editing of the orthologs of human GWAS candidates in isogenic medaka with automated high-throughput heart rate analysis. Our functional analyses of understudied human candidates uncovered a prominent fraction of heart rate associated genes from adult human patients impacting on the heart rate in embryonic medaka already in the injected generation. Following this pipeline, we identified 16 GWAS candidates with potential diagnostic and predictive power for human CVDs.

Differential regulation of mRNA fate by the human Ccr4-Not complex is driven by coding sequence composition and mRNA localization

BACKGROUND

Regulation of protein output at the level of translation allows for a rapid adaptation to dynamic changes to the cell's requirements. This precise control of gene expression is achieved by complex and interlinked biochemical processes that modulate both the protein synthesis rate and stability of each individual mRNA. A major factor coordinating this regulation is the Ccr4-Not complex. Despite playing a role in most stages of the mRNA life cycle, no attempt has been made to take a global integrated view of how the Ccr4-Not complex affects gene expression.

RESULTS

This study has taken a comprehensive approach to investigate post-transcriptional regulation mediated by the Ccr4-Not complex assessing steady-state mRNA levels, ribosome position, mRNA stability, and protein production transcriptome-wide. Depletion of the scaffold protein CNOT1 results in a global upregulation of mRNA stability and the preferential stabilization of mRNAs enriched for G/C-ending codons. We also uncover that mRNAs targeted to the ER for their translation have reduced translational efficiency when CNOT1 is depleted, specifically downstream of the signal sequence cleavage site. In contrast, translationally upregulated mRNAs are normally localized in p-bodies, contain disorder-promoting amino acids, and encode nuclear localized proteins. Finally, we identify ribosome pause sites that are resolved or induced by the depletion of CNOT1.

CONCLUSIONS

We define the key mRNA features that determine how the human Ccr4-Not complex differentially regulates mRNA fate and protein synthesis through a mechanism linked to codon composition, amino acid usage, and mRNA localization.

Co-Occurring Heterozygous CNOT3 and SMAD6 Truncating Variants: Unusual Presentation and Refinement of the IDDSADF Phenotype

Objective, the application of genomic sequencing in clinical practice has allowed us to appreciate the contribution of co-occurring pathogenic variants to complex and unclassified clinical phenotypes. Besides the clinical relevance, these findings have provided evidence of previously unrecognized functional links between genes in the context of developmental processes and physiology. Patients and Methods, a 5-year-old patient showing an unclassified phenotype characterized by developmental delay, speech delay, peculiar behavioral features, facial dysmorphism and severe cardiopathy was analyzed by trio-based whole exome sequencing (WES) analysis to identify the genomic events underlying the condition. Results, two co-occurring heterozygous truncating variants in CNOT3 and SMAD6 were identified. Heterozygous loss-of-function variants in CNOT3, encoding a subunit of the CCR4-NOT protein complex, have recently been reported to cause a syndromic condition known as intellectual developmental disorder with speech delay, autism and dysmorphic facies (IDDSADF). Enrichment of rare/private variants in the SMAD6 gene, encoding a protein negatively controlling transforming growth factor β/bone morphogenetic protein (TGFB/BMP) signaling, has been described in association with a wide spectrum of congenital heart defects. We dissected the contribution of individual variants to the complex clinical manifestations and profiled a previously unappreciated set of facial features and signs characterizing IDDSADF. Conclusions, two concomitant truncating variants in CNOT3 and SMAD6 are the cause of the combination of features documented in the patient resulting in the unique multisystem neurodevelopmental condition. These findings provide evidence for a functional link between the CCR4-NOT complex and TGFB/BMP signaling in processes controlling cardiac development. Finally, the present revision provides evidence that IDDSADF is characterized by a distinctive facial gestalt.

Determining protein-protein functional associations by functional rules based on gene ontology and KEGG pathway

Protein-protein interactions (PPIs) describe the direct physical contact of two proteins that usually results in specific biological functions or regulatory processes. The characterization and study of PPIs through the investigation of their pattern and principle have remained a question in biological studies. Various experimental and computational methods have been used for PPI studies, but most of them are based on the sequence similarity with current validated PPI participators or cellular localization patterns. Most methods ignore the fact that PPIs are defined by their specific biological functions. In this study, we constructed a novel rule-based computational method using gene ontology and KEGG pathway annotation of PPI participators that correspond to the complicated biological effects of PPIs. Our newly presented computational method identified a group of biological functions that are tightly associated with PPIs and provided a new function-based tool for PPI studies in a rule manner.

CNOT7 modulates biological functions of ovarian cancer cells via AKT signaling pathway

AIMS

CNOT7 plays an important role in many biological processes, providing attractive opportunities for the treatment of malignant tumors. However, the functions and mechanism of CNOT7 in ovarian cancer (OC) have not been elucidated. The purpose of this study was to assess the role of CNOT7 in OC.

MATERIALS AND METHODS

SKOV3 and A2780 cells were chosen as the cell lines for the experiments of this manuscript via the analysis of the expression of CNOT7 protein and the mRNA level in ovarian surface epithelium (OSE) cells, SKOV3, HO8910 and A2780 cells. The expression of CNOT7 was detected by western blot assays and RT-PCR in A2780 and SKOV3 cells. The MTT assays, colony formation assays and EdU assays were used to measure cell proliferation when CNOT7 was knocked down or overexpressed in A2780 and SKOV3 cells. Furthermore, cell migration and invasion ability were achieved from transwell assays. Cell cycle and apoptosis rate after small interference RNA-CNOT7 (siRNA-CNOT7) were detected by flow cytometry assays. Finally, the cell proliferation, migration and invasion ability were detected when A2780 and SKOV3 cells with CNOT7 overexpression were treated with LY294002.

KEY FINDINGS

The expression of CNOT7 protein in OC cells, including SKOV3, HO8910 and A2780 cells were significantly higher than that in OSE cells (P < 0.05). The mRNA level of CNOT7 in HO8910 and A2780 cells were significantly higher than that in OSE cells (P < 0.01). However, the mRNA level of CNOT7 in SKOV3 cells was no significant difference compared with OSE cells (P > 0.05). The results suggested that knockdown of CNOT7 could inhibit the cell proliferation, migration and invasion ability in A2780 and SKOV3 cells, and increase cell apoptosis and autophagy. The expression of apoptosis-related molecules (PARP, Caspase3 and Caspase9) and autophagy-related protein (LC3B) were up-regulated after CNOT7 knockdown, while the expression of cycle-related protein (CDK6) and the anti-apoptotic gene (Bcl2) were downregulated. Meanwhile, the opposite results were observed when CNOT7 was overexpressed in A2780 and SKOV3 cells. It is worth noting that the effect of CNOT7 overexpression in A2780 and SKOV3 cells could be partially or completely eliminated by treatment with AKT inhibitor LY294002.

SIGNIFICANCE

CNOT7 has a carcinogenic effect in OC, and the carcinogenic effect may be achieved via the AKT signaling pathway.

The Regulatory Properties of the Ccr4-Not Complex

The mammalian Ccr4–Not complex, carbon catabolite repression 4 (Ccr4)-negative on TATA-less (Not), is a large, highly conserved, multifunctional assembly of proteins that acts at different cellular levels to regulate gene expression. In the nucleus, it is involved in the regulation of the cell cycle, chromatin modification, activation and inhibition of transcription initiation, control of transcription elongation, RNA export, nuclear RNA surveillance, and DNA damage repair. In the cytoplasm, the Ccr4–Not complex plays a central role in mRNA decay and affects protein quality control. Most of our original knowledge of the Ccr4–Not complex is derived, primarily, from studies in yeast. More recent studies have shown that the mammalian complex has a comparable structure and similar properties. In this review, we summarize the evidence for the multiple roles of both the yeast and mammalian Ccr4–Not complexes, highlighting their similarities.

First person – Lisa Elmén

First Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms, helping early-career researchers promote themselves alongside their papers. Lisa Elmén is first author on ‘Silencing of CCR4-NOT complex subunits affects heart structure and function’, published in DMM. Lisa conducted the research described in this article while a lab manager/research associate in Rolf Bodmer's lab at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA. She is now a scientist at Bloom Science, San Diego, CA, USA researching bacteria for the development of live biotherapeutics for neurological diseases.