Bone formation in mammals requires continuous production of osteoblasts throughout life. A common molecular marker for all osteogenic mesenchymal progenitors has not been identified. Here, by ...lineage-tracing experiments in fetal or postnatal mice, we discover that Gli1
cells progressively produce osteoblasts in all skeletal sites. Most notably, in postnatal growing mice, the Gli1
cells residing immediately beneath the growth plate, termed here "metaphyseal mesenchymal progenitors" (MMPs), are essential for cancellous bone formation. Besides osteoblasts, MMPs also give rise to bone marrow adipocytes and stromal cells in vivo. RNA-seq reveals that MMPs express a number of marker genes previously assigned to mesenchymal stem/progenitor cells, including CD146/Mcam, CD44, CD106/Vcam1, Pdgfra, and Lepr. Genetic disruption of Hh signaling impairs proliferation and osteoblast differentiation of MMPs. Removal of β-catenin causes MMPs to favor adipogenesis, resulting in osteopenia coupled with increased marrow adiposity. Finally, postnatal Gli1
cells contribute to both chondrocytes and osteoblasts during bone fracture healing. Thus Gli1 marks mesenchymal progenitors responsible for both normal bone formation and fracture repair.
In humans, the cGAS-STING immunity pathway signals in response to cytosolic DNA via 2′,3′ cGAMP, a cyclic dinucleotide (CDN) second messenger containing mixed 2′–5′ and 3′–5′ phosphodiester bonds. ...Prokaryotes also produce CDNs, but these are exclusively 3′ linked, and thus the evolutionary origins of human 2′,3′ cGAMP signaling are unknown. Here we illuminate the ancient origins of human cGAMP signaling by discovery of a functional cGAS-STING pathway in Nematostella vectensis, an anemone species >500 million years diverged from humans. Anemone cGAS appears to produce a 3′,3′ CDN that anemone STING recognizes through nucleobase-specific contacts not observed in human STING. Nevertheless, anemone STING binds mixed-linkage 2′,3′ cGAMP indistinguishably from human STING, trapping a unique structural conformation not induced by 3′,3′ CDNs. These results reveal that human mixed-linkage cGAMP achieves universal signaling by exploiting a deeply conserved STING conformational intermediate, providing critical insight for therapeutic targeting of the STING pathway.
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•Binding of CDNs is an evolutionarily ancient STING function, predating interferons•cGAS-STING function is conserved in anemone, >500 million years diverged from humans•Anemone cGAS produces a canonical 3′,3′ linked CDN similar to those in bacteria•Vertebrate 2′,3′ cGAMP signaling exploits a deeply conserved STING conformation
Kranzusch and Wilson et al. use structural and biochemical approaches to characterize human and anemone cGAS-STING immune pathways, demonstrating that the product of human cGAS is a potent STING activator because it targets an ancient, conserved, intermediate conformation of STING.
Once melanomas have progressed with acquired resistance to mitogen-activated protein kinase (MAPK)-targeted therapy, mutational heterogeneity presents a major challenge. We therefore examined the ...therapy phase before acquired resistance had developed and discovered the melanoma survival oncogene MITF as a driver of an early non-mutational and reversible drug-tolerance state, which is induced by PAX3-mediated upregulation of MITF. A drug-repositioning screen identified the HIV1-protease inhibitor nelfinavir as potent suppressor of PAX3 and MITF expression. Nelfinavir profoundly sensitizes BRAF and NRAS mutant melanoma cells to MAPK-pathway inhibitors. Moreover, nelfinavir is effective in BRAF and NRAS mutant melanoma cells isolated from patients progressed on MAPK inhibitor (MAPKi) therapy and in BRAF/NRAS/PTEN mutant tumors. We demonstrate that inhibiting a driver of MAPKi-induced drug tolerance could improve current approaches of targeted melanoma therapy.
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•MITF is a driver of a reversible non-mutational drug-tolerance phase in melanoma•Drug repositioning identifies nelfinavir mesylate as a suppressor of MITF expression•Nelfinavir sensitizes BRAF and NRAS mutant melanoma to MAPK inhibitor treatment•A nelfinavir combination therapy overcomes NRAS-driven acquired resistance
Smith et al. discover PAX3-mediated overexpression of MITF as a reversible resistance mechanism to MAPK-pathway inhibition in BRAF mutant melanomas and identify nelfinavir, which inhibits this mechanism and sensitizes not only BRAF mutant but also BRAF and NRAS mutant melanoma cells to MAPK-pathway inhibitors.
This manuscript is the result of the North American Neuroendocrine Tumor Society consensus conference on the surgical management of pancreatic neuroendocrine tumors from July 19 to 20, 2018. The ...group reviewed a series of questions of specific interest to surgeons taking care of patients with pancreatic neuroendocrine tumors, and for each, the available literature was reviewed. What follows are these reviews for each question followed by recommendations of the panel.
Aqueous film-forming foams (AFFFs), containing per- and polyfluoroalkyl substances (PFASs), are released into the environment during response to fire-related emergencies. Repeated historical ...applications of AFFF at military sites were a result of fire-fighter training exercises and equipment testing. Recent data on AFFF-impacted groundwater indicates that ∼25% of the PFASs remain unidentified. In an attempt to close the mass balance, a systematic evaluation of 3M and fluorotelomer-based AFFFs, commercial products, and AFFF-impacted groundwaters from 15 U.S. military bases was conducted to identify the remaining PFASs. Liquid chromatography quadrupole time-of-flight mass spectrometry was used for compound discovery. Nontarget analysis utilized Kendrick mass defect plots and a “nontarget” R script. Suspect screening compared masses with those of previously reported PFASs. Forty classes of novel anionic, zwitterionic, and cationic PFASs were discovered, and an additional 17 previously reported classes were observed for the first time in AFFF and/or AFFF-impacted groundwater. All 57 classes received an acronym and IUPAC-like name derived from collective author knowledge. Thirty-four of the 40 newly identified PFAS classes derive from electrochemical fluorination (ECF) processes, most of which have the same base structure. Of the newly discovered PFASs found only in AFFF-impacted groundwater, 11 of the 13 classes are ECF-derived, and the remaining two classes are fluorotelomer-derived, which suggests that both ECF- and fluorotelomer-based PFASs are persistent in the environment.
Innate immune recognition of foreign nucleic acids induces protective interferon responses. Detection of cytosolic DNA triggers downstream immune signaling through activation of cyclic GMP-AMP ...synthase (cGAS). We report here the crystal structure of human cGAS, revealing an unanticipated zinc-ribbon DNA-binding domain appended to a core enzymatic nucleotidyltransferase scaffold. The catalytic core of cGAS is structurally homologous to the RNA-sensing enzyme, 2′-5′ oligo-adenylate synthase (OAS), and divergent C-terminal domains account for specific ligand-activation requirements of each enzyme. We show that the cGAS zinc ribbon is essential for STING-dependent induction of the interferon response and that conserved amino acids displayed within the intervening loops are required for efficient cytosolic DNA recognition. These results demonstrate that cGAS and OAS define a family of innate immunity sensors and that structural divergence from a core nucleotidyltransferase enables second-messenger responses to distinct foreign nucleic acids.
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•Crystal structure of the human cytosolic DNA sensor•cGAS and OAS form a family of innate immune receptors•Unique zinc-ribbon motif insertion within cGAS confers DNA specificity
The enzyme cyclic GMP-AMP synthase (cGAS) recognizes cytosolic dsDNA and produces a cyclic dinucleotide second messenger to activate innate immunity. Doudna, Berger, and colleagues now present the crystal structure of human cGAS, revealing a Zinc-ribbon insertion essential for dsDNA recognition and a core nucleotidyltransferase domain structurally homologous to the dsRNA sensor oligo-adenylate synthase (OAS). These results show that cGAS and OAS constitute a family of catalytic OAS-like second-messenger receptors (OLRs), forming the front line of immune defense.
The coronavirus disease 2019 (COVID-19) pandemic has led to accelerated efforts to develop therapeutics and vaccines. A key target of these efforts is the spike (S) protein, which is metastable and ...difficult to produce recombinantly. We characterized 100 structure-guided spike designs and identified 26 individual substitutions that increased protein yields and stability. Testing combinations of beneficial substitutions resulted in the identification of HexaPro, a variant with six beneficial proline substitutions exhibiting higher expression than its parental construct (by a factor of 10) as well as the ability to withstand heat stress, storage at room temperature, and three freeze-thaw cycles. A cryo-electron microscopy structure of HexaPro at a resolution of 3.2 angstroms confirmed that it retains the prefusion spike conformation. High-yield production of a stabilized prefusion spike protein will accelerate the development of vaccines and serological diagnostics for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Obesity has been linked to increased mortality in several cancer types; however, the relation between obesity and survival outcomes in metastatic melanoma is unknown. The aim of this study was to ...examine the association between body-mass index (BMI) and progression-free survival or overall survival in patients with metastatic melanoma who received targeted therapy, immunotherapy, or chemotherapy.
This retrospective study analysed independent cohorts of patients with metastatic melanoma assigned to treatment with targeted therapy, immunotherapy, or chemotherapy in randomised clinical trials and one retrospective study of patients treated with immunotherapy. Patients were classified according to BMI, following the WHO definitions, as underweight, normal, overweight, or obese. Patients without BMI and underweight patients were excluded. The primary outcomes were the associations between BMI and progression-free survival or overall survival, stratified by treatment type and sex. We did multivariable analyses in the independent cohorts, and combined adjusted hazard ratios in a mixed-effects meta-analysis to provide a precise estimate of the association between BMI and survival outcomes; heterogeneity was assessed with meta-regression analyses. Analyses were done on the predefined intention-to-treat population in the randomised controlled trials and on all patients included in the retrospective study.
The six cohorts consisted of a total of 2046 patients with metastatic melanoma treated with targeted therapy, immunotherapy, or chemotherapy between Aug 8, 2006, and Jan 15, 2016. 1918 patients were included in the analysis. Two cohorts containing patients from randomised controlled trials treated with targeted therapy (dabrafenib plus trametinib n=599 and vemurafenib plus cobimetinib n=240), two cohorts containing patients treated with immunotherapy (one randomised controlled trial of ipilimumab plus dacarbazine n=207 and a retrospective cohort treated with pembrolizumab, nivolumab, or atezolizumab n=331), and two cohorts containing patients treated with chemotherapy (two randomised controlled trials of dacarbazine n=320 and n=221) were classified according to BMI as normal (694 36% patients), overweight (711 37%), or obese (513 27%). In the pooled analysis, obesity, compared with normal BMI, was associated with improved survival in patients with metastatic melanoma (average adjusted hazard ratio HR 0·77 95% CI 0·66–0·90 for progression-free survival and 0·74 0·58–0·95 for overall survival). The survival benefit associated with obesity was restricted to patients treated with targeted therapy (HR 0·72 0·57–0·91 for progression-free survival and 0·60 0·45–0·79 for overall survival) and immunotherapy (HR 0·75 0·56–1·00 and 0·64 0·47–0·86). No associations were observed with chemotherapy (HR 0·87 0·65–1·17, pinteraction=0·61 for progression-free survival and 1·03 0·80–1·34, pinteraction=0·01 for overall survival). The association of BMI with overall survival for patients treated with targeted and immune therapies differed by sex, with inverse associations in men (HR 0·53 0·40–0·70), but no associations observed in women (HR 0·85 0·61–1·18, pinteraction=0·03).
Our results suggest that in patients with metastatic melanoma, obesity is associated with improved progression-free survival and overall survival compared with those outcomes in patients with normal BMI, and that this association is mainly seen in male patients treated with targeted or immune therapy. These results have implications for the design of future clinical trials for patients with metastatic melanoma and the magnitude of the benefit found supports further investigation of the underlying mechanism of these associations.
ASCO/CCF Young Investigator Award, ASCO/CCF Career Development Award, MD Anderson Cancer Center (MDACC) Melanoma Moonshot Program, MDACC Melanoma SPORE, and the Dr Miriam and Sheldon G Adelson Medical Research Foundation.
To equalize X-chromosome dosages between the sexes, the female mammal inactivates one of her two X chromosomes. X-chromosome inactivation (XCI) is initiated by expression of Xist, a 17-kb noncoding ...RNA (ncRNA) that accumulates on the X in cis. Because interacting factors have not been isolated, the mechanism by which Xist induces silencing remains unknown. We discovered a 1.6-kilobase ncRNA (RepA) within Xist and identified the Polycomb complex, PRC2, as its direct target. PRC2 is initially recruited to the X by RepA RNA, with Ezh2 serving as the RNA binding subunit. The antisense Tsix RNA inhibits this interaction. RepA depletion abolishes full-length Xist induction and trimethylation on lysine 27 of histone H3 of the X. Likewise, PRC2 deficiency compromises Xist up-regulation. Therefore, RepA, together with PRC2, is required for the initiation and spread of XCI. We conclude that a ncRNA cofactor recruits Polycomb complexes to their target locus.
MicroRNAs play central roles in controlling gene expression in human cells. Sequencing data show that many miRNAs are produced at different levels and as multiple isoforms that can vary in length at ...their 5' or 3' ends, but the biogenesis and functional significance of these RNAs are largely unknown. We show here that the human trans-activation response (TAR) RNA binding protein (TRBP), a known molecular partner of the miRNA processing enzyme Dicer, changes the rates of pre-miRNA cleavage in an RNA-structure-specific manner. Furthermore, TRBP can trigger the generation of iso-miRNAs (isomiRs) that are longer than the canonical sequence by one nucleotide. We show that this change in miRNA processing site can alter guide strand selection, resulting in preferential silencing of a different mRNA target. These results implicate TRBP as a key regulator of miRNA processing and targeting in humans.
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