Structural basis of activation of the tumor suppressor protein neurofibromin.

Mutations in the NF1 gene cause the familial genetic disease neurofibromatosis type I, as well as predisposition to cancer. The NF1 gene product, neurofibromin, is a GTPase-activating protein and acts as a tumor suppressor by negatively regulating the small GTPase, Ras. However, structural insights into neurofibromin activation remain incompletely defined. Here, we provide cryoelectron microscopy (cryo-EM) structures that reveal an extended neurofibromin homodimer in two functional states: an auto-inhibited state with occluded Ras-binding site and an asymmetric open state with an exposed Ras-binding site. Mechanistically, the transition to the active conformation is stimulated by nucleotide binding, which releases a lock that tethers the catalytic domain to an extended helical repeat scaffold in the occluded state. Structure-guided mutational analysis supports functional relevance of allosteric control. Disease-causing mutations are mapped and primarily impact neurofibromin stability. Our findings suggest a role for nucleotides in neurofibromin regulation and may lead to therapeutic modulation of Ras signaling.

K128 ubiquitination constrains RAS activity by expanding its binding interface with GAP proteins.

The RAS pathway is among the most frequently activated signaling nodes in cancer. However, the mechanisms that alter RAS activity in human pathologies are not entirely understood. The most prevalent post-translational modification within the GTPase core domain of NRAS and KRAS is ubiquitination at lysine 128 (K128), which is significantly decreased in cancer samples compared to normal tissue. Here, we found that K128 ubiquitination creates an additional binding interface for RAS GTPase-activating proteins (GAPs), NF1 and RASA1, thus increasing RAS binding to GAP proteins and promoting GAP-mediated GTP hydrolysis. Stimulation of cultured cancer cells with growth factors or cytokines transiently induces K128 ubiquitination and restricts the extent of wild-type RAS activation in a GAP-dependent manner. In KRAS mutant cells, K128 ubiquitination limits tumor growth by restricting RAL/ TBK1 signaling and negatively regulating the autocrine circuit induced by mutant KRAS. Reduction of K128 ubiquitination activates both wild-type and mutant RAS signaling and elicits a senescence-associated secretory phenotype, promoting RAS-driven pancreatic tumorigenesis.

Inactivation of Capicua in adult mice causes T-cell lymphoblastic lymphoma.

CIC (also known as Capicua) is a transcriptional repressor negatively regulated by RAS/MAPK signaling. Whereas the functions of Cic have been well characterized in Drosophila, little is known about its role in mammals. CIC is inactivated in a variety of human tumors and has been implicated recently in the promotion of lung metastases. Here, we describe a mouse model in which we inactivated Cic by selectively disabling its DNA-binding activity, a mutation that causes derepression of its target genes. Germline Cic inactivation causes perinatal lethality due to lung differentiation defects. However, its systemic inactivation in adult mice induces T-cell acute lymphoblastic lymphoma (T-ALL), a tumor type known to carry CIC mutations, albeit with low incidence. Cic inactivation in mice induces T-ALL by a mechanism involving derepression of its well-known target, Etv4 Importantly, human T-ALL also relies on ETV4 expression for maintaining its oncogenic phenotype. Moreover, Cic inactivation renders T-ALL insensitive to MEK inhibitors in both mouse and human cell lines. Finally, we show that Ras-induced mouse T-ALL as well as human T-ALL carrying mutations in the RAS/MAPK pathway display a genetic signature indicative of Cic inactivation. These observations illustrate that CIC inactivation plays a key role in this human malignancy.

5-Aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase promotes pulmonary arterial smooth muscle cell proliferation via the Ras signaling pathway.

Pulmonary arterial hypertension (PAH) is a debilitating vascular disorder characterized by abnormal pulmonary artery smooth muscle cell (PASMC) proliferation and collagen synthesis, contributing to vascular remodeling and elevated pulmonary vascular resistance. This study investigated the critical role of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC) in cell proliferation and collagen synthesis in PASMCs in PAH. Here we show that ATIC levels are significantly increased in the lungs of monocrotaline (MCT)-induced PAH rat model, hypoxia-induced PAH mouse model, and platelet-derived growth factor (PDGF)-stimulated PASMCs. Inhibition of ATIC attenuated PDGF-induced cell proliferation and collagen I synthesis in PASMCs. Conversely, overexpression or knockdown of ATIC causes a significant promotion or inhibition of Ras and ERK activation, cell proliferation, and collagen synthesis in PASMCs. Moreover, ATIC deficiency attenuated Ras activation in the lungs of hypoxia-induced PAH mice. Furthermore, Ras inhibition attenuates ATIC overexpression- and PDGF-induced collagen synthesis and PASMC proliferation. Notably, we identified that transcription factors MYC, early growth response protein 1 (EGR1), and specificity protein 1 (SP1) directly binds to promoters of Atic gene and regulate ATIC expression. These results provide the first evidence that ATIC promotes PASMC proliferation in pulmonary vascular remodeling through the Ras signaling pathway.NEW & NOTEWORTHY Our findings highlight the important role of ATIC in the PASMC proliferation of pulmonary vascular remodeling through its modulation of the Ras signaling pathway and its regulation by transcription factors MYC, EGR1, and SP1. ATIC's modulation of Ras signal pathway represents a novel mechanism contributing to PAH development.

The ribosomal S6 kinase 2 (RSK2)-SPRED2 complex regulates the phosphorylation of RSK substrates and MAPK signaling.

Sprouty-related EVH-1 domain-containing (SPRED) proteins are a family of proteins that negatively regulate the RAS-Mitogen-Activated Protein Kinase (MAPK) pathway, which is involved in the regulation of the mitogenic response and cell proliferation. However, the mechanism by which these proteins affect RAS-MAPK signaling has not been elucidated. Patients with mutations in SPRED give rise to unique disease phenotypes; thus, we hypothesized that distinct interactions across SPRED proteins may account for alternative nodes of regulation. To characterize the SPRED interactome and evaluate how members of the SPRED family function through unique binding partners, we performed affinity purification mass spectrometry. We identified 90-kDa ribosomal S6 kinase 2 (RSK2) as a specific interactor of SPRED2 but not SPRED1 or SPRED3. We identified that the N-terminal kinase domain of RSK2 mediates the interaction between amino acids 123 to 201 of SPRED2. Using X-ray crystallography, we determined the structure of the SPRED2-RSK2 complex and identified the SPRED2 motif, F145A, as critical for interaction. We found that the formation of this interaction is regulated by MAPK signaling events. We also find that this interaction between SPRED2 and RSK2 has functional consequences, whereby the knockdown of SPRED2 resulted in increased phosphorylation of RSK substrates, YB1 and CREB. Furthermore, SPRED2 knockdown hindered phospho-RSK membrane and nuclear subcellular localization. We report that disruption of the SPRED2-RSK complex has effects on RAS-MAPK signaling dynamics. Our analysis reveals that members of the SPRED family have unique protein binding partners and describes the molecular and functional determinants of SPRED2-RSK2 complex dynamics.

The RAS-signaling-pathway-mutation-related prognosis in B-cell acute lymphoblastic leukemia: A report from South China children's leukemia group.

The next-generation sequencing technologies application discovers novel genetic alterations frequently in pediatric acute lymphoblastic leukemia (ALL). RAS signaling pathway mutations at the time of relapse ALL frequently appear as small subclones at the time of onset, which are considered as the drivers in ALL relapse. Whether subclones alterations in the RAS signaling pathway should be considered for risk group stratification of ALL treatment is not decided yet. In this work, we investigate the RAS signaling pathway mutation spectrum and the related prognosis in pediatric ALL. We employed an NGS panel comprising 220 genes. NGS results were collected from 202 pediatric ALL patients. 155 patients (76.7%) harbored at least one mutation. The incidences of RAS signaling pathway mutations are different significantly between T-ALL and B-ALL. In B-ALL, the RAS pathway is mostly involved, and NRAS (17.6%), KRAS (22.7%), and PTPN11 (7.7%) were the three most frequently mutated genes. Co-occurring mutations of CREBBP and NRAS, FLT3, or PTPN11 (p = 0.002, p = 0.009, and p = 0.003, respectively) were found in this cohort. The 3-year RFS rates for the RAS signaling pathway mutation-positive and negative cases was 76.5 % versus 89.7 % (p = 0.012). Four cases relapsed in the lately 3 years were RAS signaling pathway mutation-positive. RAS signaling pathway mutation is an important biomarker for poorer relapse-free survival in pediatric B-ALL patients despite good early MRD levels.

Immunological and hematological findings as major features in a patient with a new germline pathogenic CBL variant.

Casitas B-lineage lymphoma (CBL) encodes an adaptor protein with E3-ligase activity negatively controlling intracellular signaling downstream of receptor tyrosine kinases. Somatic CBL mutations play a driver role in a variety of cancers, particularly myeloid malignancies, whereas germline defects in the same gene underlie a RASopathy having clinical overlap with Noonan syndrome (NS) and predisposing to juvenile myelomonocytic leukemia and vasculitis. Other features of the disorder include cardiac defects, postnatal growth delay, cryptorchidism, facial dysmorphisms, and predisposition to develop autoimmune disorders. Here we report a novel CBL variant (c.1202G>T; p.Cys401Phe) occurring de novo in a subject with café-au-lait macules, feeding difficulties, mild dysmorphic features, psychomotor delay, autism spectrum disorder, thrombocytopenia, hepatosplenomegaly, and recurrent hypertransaminasemia. The identified variant affects an evolutionarily conserved residue located in the RING finger domain, a known mutational hot spot of both germline and somatic mutations. Functional studies documented enhanced EGF-induced ERK phosphorylation in transiently transfected COS1 cells. The present findings further support the association of pathogenic CBL variants with immunological and hematological manifestations in the context of a presentation with only minor findings reminiscent of NS or a clinically related RASopathy.

RAS pathway: The new frontier of brain mosaicism in epilepsy.

As cells divide during development, errors in DNA replication and repair lead to somatic mosaicism - a phenomenon in which different cell lineages harbor unique constellations of genetic variants. Over the past decade, somatic variants that disrupt mTOR signaling, protein glycosylation, and other functions during brain development have been linked to cortical malformations and focal epilepsy. More recently, emerging evidence points to a role for Ras pathway mosaicism in epilepsy. The Ras family of proteins is a critical driver of MAPK signaling. Disruption of the Ras pathway is most known for its association with tumorigenesis; however, developmental disorders known as RASopathies commonly have a neurological component that sometimes includes epilepsy, offering evidence for Ras involvement in brain development and epileptogenesis. Brain somatic variants affecting the Ras pathway (e.g., KRAS, PTPN11, BRAF) are now strongly associated with focal epilepsy through genotype-phenotype association studies as well as mechanistic evidence. This review summarizes the Ras pathway and its involvement in epilepsy and neurodevelopmental disorders, focusing on new evidence regarding Ras pathway mosaicism and the potential future clinical implications.

Enhanced MAPK1 Function Causes a Neurodevelopmental Disorder within the RASopathy Clinical Spectrum.

Signal transduction through the RAF-MEK-ERK pathway, the first described mitogen-associated protein kinase (MAPK) cascade, mediates multiple cellular processes and participates in early and late developmental programs. Aberrant signaling through this cascade contributes to oncogenesis and underlies the RASopathies, a family of cancer-prone disorders. Here, we report that de novo missense variants in MAPK1, encoding the mitogen-activated protein kinase 1 (i.e., extracellular signal-regulated protein kinase 2, ERK2), cause a neurodevelopmental disease within the RASopathy phenotypic spectrum, reminiscent of Noonan syndrome in some subjects. Pathogenic variants promote increased phosphorylation of the kinase, which enhances translocation to the nucleus and boosts MAPK signaling in vitro and in vivo. Two variant classes are identified, one of which directly disrupts binding to MKP3, a dual-specificity protein phosphatase negatively regulating ERK function. Importantly, signal dysregulation driven by pathogenic MAPK1 variants is stimulus reliant and retains dependence on MEK activity. Our data support a model in which the identified pathogenic variants operate with counteracting effects on MAPK1 function by differentially impacting the ability of the kinase to interact with regulators and substrates, which likely explains the minor role of these variants as driver events contributing to oncogenesis. After nearly 20 years from the discovery of the first gene implicated in Noonan syndrome, PTPN11, the last tier of the MAPK cascade joins the group of genes mutated in RASopathies.

Class I PI3K Biology.

This chapter is an introduction to phosphoinositide 3-kinases (PI3K), with class I PI3Ks as the central focus. First, the various PI3K isoforms in class I are presented with emphasis on their overall structure, subunits, subunit constitutive domains, domain-domain interactions, and functional relevance. This structural analysis is followed by a comprehensive history of seminal investigations into PI3K activity. Next, we highlight the divergent roles of the isoforms: PI3Kα, PI3Kß, PI3Kδ, and PI3Kγ. This section details signaling pathways in which these PI3K isoforms are involved, including the key upstream regulators of PI3K activity and some downstream cellular effects. Nodes of the PI3K pathway are also presented. Inhibitors of some isoforms are discussed to give an overview of the basis of some immunotherapies that are being used to target cell signaling. Finally, the chapter ends with a discussion of the dysregulation of PI3Ks in diseases including APDS, asthma, arthritis, and oncogenic mutations.

Long non-coding RNA LUCAT1 regulates the RAS pathway to promote the proliferation and invasion of malignant glioma cells through ABCB1.

Long non-coding RNAs (lncRNAs) are closely related to the occurrence and development of tumors and have gradually become a hot topic in the field of glioma research in recent years. In this study, the role of lung cancer associated transcript 1 (lncRNA LUCAT 1) in glioma occurrence and development, as well as its possible regulatory mechanism, was explored. We utilized the gene chip technology in the preliminary experiment, and based on the experiment results, selected LUCAT1（NONHSAT102745）, which was significantly upregulated in glioma, and ATP-binding cassette Subfamily B member l (ABCB1), which was significantly down-regulated in co-expression analysis, for study. Next, the expression of LUCAT1 and ABCB1 in cells and tissues was immediately evaluated. Subsequently, the cells were transfected with scrambled siRNA, LUCAT1-siRNA/ABCB 1-siRNA, or overexpressed LUCAT1/ABCB1 plasmid + RAS signaling pathway inhibitor-farnesylthiosalicylic acid (FTS). By comparing with the normal combination negative control group, the cell proliferation and invasion ability were evaluated. Finally, subcutaneous tumor formation experiments in the nude mice confirmed the association between LUCAT1 and ABCB1 and RAS signaling pathways. The expression of LUCAT 1 was up-regulated with an increase in WHO grade, and the lncRNA-mRNA co-expression analysis showed that the expression of ABCB1 was low. LUCAT 1 gene knockout reduced the mRNA and protein levels of Ras signaling pathway related factors (Ras, Raf-1, p-AKT, and p-ERK) as regulating ABCB1 expression and inhibiting the ability of tumor in proliferation and invasion no matter in vitro or in vivo. For overexpressing of LUCAT 1, the opposite was true. After we knocked out ABCB1, the LUCAT1 expression was reversely regulated while the level of RAS signaling pathway related factors increased, and the ability of tumors in proliferation and invasion was enhanced. The abnormal LUCAT1 expression affected the biological behaviors of glioma cells, such as proliferation, invasion, etc. by regulating ABCB1 and promoting the activation of the RAS signaling pathway. This provided a new drug target and therapeutic approach for gene therapy of glioma, which is expected to significantly improve the prognosis of relevant patients.

The molecular genetics of RASopathies: An update on novel disease genes and new disorders.

Enhanced signaling through RAS and the mitogen-associated protein kinase (MAPK) cascade underlies the RASopathies, a family of clinically related disorders affecting development and growth. In RASopathies, increased RAS-MAPK signaling can result from the upregulated activity of various RAS GTPases, enhanced function of proteins positively controlling RAS function or favoring the efficient transmission of RAS signaling to downstream transducers, functional upregulation of RAS effectors belonging to the MAPK cascade, or inefficient signaling switch-off operated by feedback mechanisms acting at different levels. The massive effort in RASopathy gene discovery performed in the last 20 years has identified more than 20 genes implicated in these disorders. It has also facilitated the characterization of several molecular activating mechanisms that had remained unappreciated due to their minor impact in oncogenesis. Here, we provide an overview on the discoveries collected during the last 5 years that have delivered unexpected insights (e.g., Noonan syndrome as a recessive disease) and allowed to profile new RASopathies, novel disease genes and new molecular circuits contributing to the control of RAS-MAPK signaling.

Targeting Ras-ERK cascade by bioactive natural products for potential treatment of cancer: an updated overview.

MAPK (mitogen-activated protein kinase) or ERK (extracellular-signal-regulated kinase) pathway is an important link in the transition from extracellular signals to intracellular responses. Because of genetic and epigenetic changes, signaling cascades are altered in a variety of diseases, including cancer. Extant studies on the homeostatic and pathologic behavior of MAPK signaling have been conducted; however, much remains to be explored in preclinical and clinical research in terms of regulation and action models. MAPK has implications for cancer therapy response, more specifically in response to experimental MAPK suppression, compensatory mechanisms are activated. The current study investigates MAPK as a very complex cell signaling pathway that plays roles in cancer treatment response, cellular normal conduit maintenance, and compensatory pathway activation. Most MAPK inhibitors, unfortunately, cause resistance by activating compensatory feedback loops in tumor cells and tumor microenvironment components. As a result, innovative combinatorial treatments for cancer management must be applied to limit the likelihood of alternate pathway initiation as a possibility for generating novel therapeutics based on incorporation in translational research. We summarize current knowledge about the implications of ERK (MAPK) in cancer, as well as bioactive products from plants, microbial organisms or marine organisms, as well as the correlation with their chemical structures, which modulate this pathway for the treatment of different types of cancer.

Why may citrate sodium significantly increase the effectiveness of transarterial chemoembolization in hepatocellular carcinoma?

Hepatocellular carcinoma (HCC) represents the third cause of cancer death in men worldwide, and its increasing incidence can be explained by the increasing occurrence of non-alcoholic steatohepatitis (NASH). HCC prognosis is poor, as its 5-year overall survival is approximately 18 % and most cases are diagnosed at an inoperable advanced stage. Moreover, tumor sensitivity to conventional chemotherapeutics (particularly to cisplatin-based regimen), trans-arterial chemoembolization (cTACE), tyrosine kinase inhibitors, anti-angiogenic molecules and immune checkpoint inhibitors is limited. Oncogenic signaling pathways, such as HIF-1α and RAS/PI3K/AKT, may provoke drug resistance by enhancing the aerobic glycolysis ("Warburg effect") in cancer cells. Indeed, this metabolism, which promotes cancer cell development and aggressiveness, also induces extracellular acidity. In turn, this acidity promotes the protonation of drugs, hence abrogating their internalization, since they are most often weakly basic molecules. Consequently, targeting the Warburg effect in these cancer cells (which in turn would reduce the extracellular acidification) could be an effective strategy to increase the delivery of drugs into the tumor. Phosphofructokinase-1 (PFK1) and its activator PFK2 are the main regulators of glycolysis, and they also couple the enhancement of glycolysis to the activation of key signaling cascades and cell cycle progression. Therefore, targeting this "Gordian Knot" in HCC cells would be of crucial importance. Here, we suggest that this could be achieved by citrate administration at high concentration, because citrate is a physiologic inhibitor of PFK1 and PFK2. As shown in various in vitro studies, including HCC cell lines, administration of high concentrations of citrate inhibits PFK1 and PFK2 (and consequently glycolysis), decreases ATP production, counteracts HIF-1α and PI3K/AKT signaling, induces apoptosis, and sensitizes cells to cisplatin treatment. Administration of high concentrations of citrate in animal models (including Ras-driven tumours) has been shown to effectively inhibit cancer growth, reverse cell dedifferentiation, and neutralize intratumor acidity, without apparent toxicity in animal studies. Citrate may also induce a rapid secretion of pro-inflammatory cytokines by macrophages, and it could favour the destruction of cancer stem cells (CSCs) sustaining tumor recurrence. Consequently, this "citrate strategy" could improve the tumor sensitivity to current treatments of HCC by reducing the extracellular acidity, thus enhancing the delivery of chemotherapeutic drugs into the tumor. Therefore, we propose that this strategy should be explored in clinical trials, in particular to enhance cTACE effectiveness.

Analysis of multi-omics data on the relationship between epigenetic changes and nervous system disorders caused by exposure to environmentally harmful substances.

Environmentally hazardous substances and exposure to these can cause various diseases. Volatile organic compounds can easily evaporate into the atmosphere, thereby exerting toxic effects through either the skin or respiratory tract exposures. Toluene, a neurotoxin, has been widely used in various industries. However, it has a detrimental effect on the nervous system (such as hallucinations or memory impairment), while data on the mechanism underlaying its harmful effects remain limited. Therefore, this study investigates the effect of toluene on the nervous system via epigenetic and genetic changes of toluene-exposed individuals. We identified significant epigenetic changes and confirmed that the affected abnormally expressed genes negatively influenced the nervous system. In particular, we confirmed that the miR-15 family, upregulated by toluene, downregulated ABL2, which could affect the R as signaling pathway resulting in neuronal structural abnormalities. Our study suggests that miR-15a-5p, miR-15b-5p, miR-16-5p, miR-301a-3p, and lncRNA NEAT1 may represent effective epigenomic markers associated with neurodegenerative diseases caused by toluene.

RNA-Seq Transcriptome Analysis of Differentiated Human Oligodendrocytic MO3.13 Cells Shows Upregulation of Genes Involved in Myogenesis.

In this work, we examined the differentiation of oligodendrocytic MO3.13 cells and changes in their gene expression after treatment with phorbol 12-myristate 13-acetate, PMA, or with RNA polymerase I (Pol I) inhibitor, CX-5461. We found that MO3.13 cells changed their morphology when treated with both agents. Interestingly, CX-5461, but not PMA, induced noticeable changes in the integrity of the nucleoli. Then, we analyzed the p53 transcriptional activity in MO3.13 cells and found that it was increased in both cell populations, but particularly in cells treated with PMA. Interestingly, this high p53 transcriptional activity in PMA-treated cells coincided with a lower level of an unmodified (non-phosphorylated) form of this protein. Since morphological changes in MO3.13 cells after PMA and CX-5461 treatment were evident, suggesting that cells were induced to differentiate, we performed RNA-seq analysis of PMA-treated cells, to reveal the direction of alterations in gene expression. The analysis showed that the largest group of upregulated genes consisted of those involved in myogenesis and K-RAS signaling, rather than those associated with oligodendrocyte lineage progression.

Conformation-specific inhibitors of activated Ras GTPases reveal limited Ras dependency of patient-derived cancer organoids.

The small GTPases H, K, and NRAS are molecular switches indispensable for proper regulation of cellular proliferation and growth. Several mutations in the genes encoding members of this protein family are associated with cancer and result in aberrant activation of signaling processes caused by a deregulated recruitment of downstream effector proteins. In this study, we engineered variants of the Ras-binding domain (RBD) of the C-Raf proto-oncogene, Ser/Thr kinase (CRAF). These variants bound with high affinity with the effector-binding site of Ras in an active conformation. Structural characterization disclosed how the newly identified RBD mutations cooperate and thereby enhance affinity with the effector-binding site in Ras compared with WT RBD. The engineered RBD variants closely mimicked the interaction mode of naturally occurring Ras effectors and acted as dominant-negative affinity reagents that block Ras signal transduction. Experiments with cancer cells showed that expression of these RBD variants inhibits Ras signaling, reducing cell growth and inducing apoptosis. Using these optimized RBD variants, we stratified patient-derived colorectal cancer organoids with known Ras mutational status according to their response to Ras inhibition. These results revealed that the presence of Ras mutations was insufficient to predict sensitivity to Ras inhibition, suggesting that not all of these tumors required Ras signaling for proliferation. In summary, by engineering the Ras/Raf interface of the CRAF-RBD, we identified potent and selective inhibitors of Ras in its active conformation that outcompete binding of Ras-signaling effectors.

Novel regulation of Ras proteins by direct tyrosine phosphorylation and dephosphorylation.

Somatic mutations in the RAS genes are frequent in human tumors, especially in pancreatic, colorectal, and non-small-cell lung cancers. Such mutations generally decrease the ability of Ras to hydrolyze GTP, maintaining the protein in a constitutively active GTP-bound form that drives uncontrolled cell proliferation. Efforts to develop drugs that target Ras oncoproteins have been unsuccessful. Recent emerging data suggest that Ras regulation is more complex than the scientific community has believed for decades. In this review, we summarize advances in the "textbook" view of Ras activation. We also discuss a novel type of Ras regulation that involves direct phosphorylation and dephosphorylation of Ras tyrosine residues. The discovery that pharmacological inhibition of the tyrosine phosphoprotein phosphatase SHP2 maintains mutant Ras in an inactive state suggests that SHP2 could be a novel drug target for the treatment of Ras-driven human cancers.

Rasa3 regulates stage-specific cell cycle progression in murine erythropoiesis.

Inherited bone marrow failure syndromes (IBMFS) are heterogeneous disorders characterized by dysregulated hematopoiesis in various lineages, developmental anomalies, and predisposition to malignancy. The scat (severe combined anemia and thrombocytopenia) mouse model is a model of IBMFS with a phenotype of pancytopenia cycling through crises and remission. Scat carries an autosomal recessive missense mutation in Rasa3 that results in RASA3 mislocalization and loss of function. RASA3 functions as a Ras-GTPase activating protein (GAP), and its loss of function in scat results in increased erythroid RAS activity and reactive oxygen species (ROS) and altered erythroid cell cycle progression, culminating in delayed terminal erythroid differentiation. Here we sought to further resolve the erythroid cell cycle defect in scat through ex vivo flow cytometric analyses. These studies revealed a specific G0/G1 accumulation in scat bone marrow (BM) polychromatophilic erythroblasts and scat BM Ter119-/c-KIT+/CD71lo/med progenitors, with no changes evident in equivalent scat spleen populations. Systematic analyses of RNAseq data from megakaryocyte-erythroid progenitors (MEPs) in scat crisis vs. scat partial remission reveal altered expression of genes involved in the G1-S checkpoint. Together, these data indicate a precise, biphasic role for RASA3 in regulating the cell cycle during erythropoiesis with relevance to hematopoietic disease progression.

miR-6718-5p and miR-4329 can be used as potential biomarkers for acute myocardial infarction.

BACKGROUND: The prevention and prognosis of the onset or recurrence of acute myocardial infarction (AMI) is a difficult problem in contemporary research. METHODS: In this study, peripheral blood samples were collected from seven patients with AMI and nine healthy adults, and exosome microRNAs (miRNAs) were extracted. The miRNA differential expression profiles of serum exosomes in patients with AMI were obtained by using the next-generation sequencing technology combined with bioinformatics analysis. Reverse-transcriptase polymerase chain reaction (RT-PCR) was used to verify the primary screening of differential exosome miRNAs to reveal the possible mechanism of their action on AMI. RESULTS: Compared with healthy individuals, 544 miRNAs were upregulated and 518 miRNAs were downregulated in AMI patients preoperatively. Among these miRNAs, we selected miR-6718 and miR-4329 for qPCR verification. The expression of miR6718 and miR-4329 in patients with myocardial infarction was significantly lower than that in normal controls.