Cnot3 enhances human embryonic cardiomyocyte proliferation by promoting cell cycle inhibitor mRNA degradation

Dissecting the Role of the Ccr4-Not Deadenylase Complex in Pluripotency and Differentiation

In this chapter, we describe methods and assays to examine the role of the Ccr4-Not mRNA deadenylase complex in regulating mouse embryonic stem cell (ESC) pluripotency and differentiation. We present the following procedures: sgRNA design and cloning, the culture of mouse ESCs, transfection and colony picking, genotyping, generation of Cnot3 conditional deletion ESCs, assessment of Cnot3 deletion efficiency, and examination of the impact on ESC maintenance and differentiation. The above approach and protocols can also be readily applied to study other Ccr4-Not subunits in ESC fate regulation, thereby facilitating the systematic dissection of Ccr4-Not function in stem cells and development.

Clinical features of CNOT3-associated neurodevelopmental disorder in three Chinese patients

CNOT3 is the central component of the CCR4-NOT protein complex, which is a global regulator of RNA polymerase II transcription. Loss of function mutations in CNOT3 lead to intellectual developmental disorder with speech delay, autism, and dysmorphic facies (IDDSADF), which is very rare. Herein, we reported two novel heterozygous frameshift mutations (c.1058_1059insT and c.724delT) and one novel splice site variant (c.387 + 2 T > C) in CNOT3 (NM_014516.3) gene in three Chinese patients with dysmorphic features, developmental delay, and behavior anomalies. The functional study showed that the CNOT3 mRNA levels were significantly decreased in the peripheral blood of two patients with c.1058_1059insT and c.387 + 2 T > C variants, respectively, and minigene assay demonstrated that the splice variant (c.387 + 2 T > C) resulted in exon skipping. We also found that CNOT3 deficiency was linked to alterations of expression levels of other CCR4-NOT complex subunits in mRNA level in the peripheral blood. By analyzing the clinical manifestations of all these patients with CNOT3 variants, including our three cases and 22 patients previously reported, we did not observe a correlation between genotypes and phenotypes. In summary, this is the first time to report cases with IDDSADF in the Chinese population, and three novel CNOT3 variants in these patients expand its mutational spectrum.

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.

Single- and Multimarker Genome-Wide Scans Evidence Novel Genetic Risk Modifiers for Venous Thromboembolism

Previous genome-wide association studies (GWASs) have established several susceptibility genes for venous thromboembolism (VTE) and suggested many others. However, a large proportion of the genetic variance in VTE remains unexplained. Here, we report genome-wide single- and multimarker as well as gene-level associations with VTE in 964 cases and 899 healthy controls of European ancestry. We report 19 loci at the genome-wide level of association (p ≤ 5 × 10^-8). Our results add to the strong support for the association of genetic variants in F5, NME7, ABO, and FGA with VTE, and identify several loci that have not been previously associated with VTE. Altogether, our novel findings suggest that 20 susceptibility genes for VTE were newly discovered by our study. These genes may impact the production and prothrombotic functions of platelets, endothelial cells, and white and red blood cells. Moreover, the majority of these genes have been previously associated with cardiovascular diseases and/or risk factors for VTE. Future studies are warranted to validate our findings and to investigate the shared genetic architecture with susceptibility factors for other cardiovascular diseases impacting VTE risk.

Heart Development and Regeneration in Non-mammalian Model Organisms

Cardiovascular disease is a serious threat to human health and a leading cause of mortality worldwide. Recent years have witnessed exciting progress in the understanding of heart formation and development, enabling cardiac biologists to make significant advance in the field of therapeutic heart regeneration. Most of our understanding of heart development and regeneration, including the genes and signaling pathways, are driven by pioneering works in non-mammalian model organisms, such as fruit fly, fish, frog, and chicken. Compared to mammalian animal models, non-mammalian model organisms have special advantages in high-throughput applications such as disease modeling, drug discovery, and cardiotoxicity screening. Genetically engineered animals of cardiovascular diseases provide valuable tools to investigate the molecular and cellular mechanisms of pathogenesis and to evaluate therapeutic strategies. A large number of congenital heart diseases (CHDs) non-mammalian models have been established and tested for the genes and signaling pathways involved in the diseases. Here, we reviewed the mechanisms of heart development and regeneration revealed by these models, highlighting the advantages of non-mammalian models as tools for cardiac research. The knowledge from these animal models will facilitate therapeutic discoveries and ultimately serve to accelerate translational medicine.

Current situation and future of stem cells in cardiovascular medicine

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. Currently, many methods have been proposed by researchers for the prevention and treatment of CVD; among them, stem cell-based therapies are the most promising. As the cells of origin for various mature cells, stem cells have the ability to self-renew and differentiate. Stem cells have a powerful ability to regenerate biologically, self-repair, and enhance damaged functional tissues or organs. Allogeneic stem cells and somatic stem cells are two types of cells that can be used for cardiac repair. Theoretically, dilated cardiomyopathy and acute myocardial infarction can be treated with such cells. In addition, stem cell transplantation procedures, including intravenous, epicardial, cardiac, and endocardial injections, have been reported to provide significant benefits in clinical practice; however, there are still a number of issues that need further study and consideration, such as the form and quantity of transplanted cells and post-transplantation health. The goal of this analysis was to summarize the recent advances in stem cell-based therapies and their efficacy in cardiovascular regenerative medicine.

Loss of β-cell identity and diabetic phenotype in mice caused by disruption of CNOT3-dependent mRNA deadenylation

Pancreatic β-cells are responsible for production and secretion of insulin in response to increasing blood glucose levels. Defects in β-cell function lead to hyperglycemia and diabetes mellitus. Here, we show that CNOT3, a CCR4-NOT deadenylase complex subunit, is dysregulated in islets in diabetic db/db mice, and that it is essential for murine β cell maturation and identity. Mice with β cell-specific Cnot3 deletion (Cnot3βKO) exhibit impaired glucose tolerance, decreased β cell mass, and they gradually develop diabetes. Cnot3βKO islets display decreased expression of key regulators of β cell maturation and function. Moreover, they show an increase of progenitor cell markers, β cell-disallowed genes, and genes relevant to altered β cell function. Cnot3βKO islets exhibit altered deadenylation and increased mRNA stability, partly accounting for the increased expression of those genes. Together, these data reveal that CNOT3-mediated mRNA deadenylation and decay constitute previously unsuspected post-transcriptional mechanisms essential for β cell identity.

mRNA Metabolism in Cardiac Development and Disease: Life After Transcription

The central dogma of molecular biology illustrates the importance of mRNAs as critical mediators between genetic information encoded at the DNA level and proteomes/metabolomes that determine the diverse functional outcome at the cellular and organ levels. Although the total number of protein-producing (coding) genes in the mammalian genome is ~20,000, it is evident that the intricate processes of cardiac development and the highly regulated physiological regulation in the normal heart, as well as the complex manifestation of pathological remodeling in a diseased heart, would require a much higher degree of complexity at the transcriptome level and beyond. Indeed, in addition to an extensive regulatory scheme implemented at the level of transcription, the complexity of transcript processing following transcription is dramatically increased. RNA processing includes post-transcriptional modification, alternative splicing, editing and transportation, ribosomal loading, and degradation. While transcriptional control of cardiac genes has been a major focus of investigation in recent decades, a great deal of progress has recently been made in our understanding of how post-transcriptional regulation of mRNA contributes to transcriptome complexity. In this review, we highlight some of the key molecular processes and major players in RNA maturation and post-transcriptional regulation. In addition, we provide an update to the recent progress made in the discovery of RNA processing regulators implicated in cardiac development and disease. While post-transcriptional modulation is a complex and challenging problem to study, recent technological advancements are paving the way for a new era of exciting discoveries and potential clinical translation in the context of cardiac biology and heart disease.