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530 result(s) for "Ronald Lu "
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Climatic and tectonic controls on the fluvial morphology of the Northeastern Tibetan Plateau (China)
The geomorphological evolution of the Northeastern Tibetan Plateau (NETP) could provide valuable information for reconstructing the tectonic movements of the region. And the considerable uplift and climatic changes at here, provide an opportunity for studying the im- pact of tectonic and monsoon climate on fluvial morphological development and sedimentary architecture of fluvial deposits. The development of peneplain-like surface and related land- scape transition from basin filling to incision indicate an intense uplift event with morphologi- cal significance at around 10-17 Ma in the NETP. After that, incision into the peneplain was not continuous but a staircase of terraces, developed as a result of climatic influences. In spite of the generally persisting uplift of the whole region, the neighbouring tectonic blocks had different uplift rates, leading to a complicated fluvial response with accumulation terraces alternating with erosion terraces at a small spatial and temporal scale. The change in fluvial activity as a response to climatic impact is reflected in the general sedimentary sequence on the terraces from high-energy (braided) channel deposits (at full glacial) to lower-energy de- posits of small channels (towards the end of the glacial), mostly separated by a rather sharp boundary from overlying flood-Ioams (at the glacial-interglacial transition) and overall soil formation (interglacial). Pronounced incision took place at the subsequent warm-cold transi- tions. In addition, it is hypothesized that in some strongly uplifted blocks energy thresholds could be crossed to allow terrace formation as a response to small climatic fluctuations (10^3-10^4 year timescale). Although studies of morpho-tectonic and geomorphological evolu- tion of the NETP, improve understanding on the impacts of tectonic motions and monsoonal climate on fluvial processes, a number of aspects, such as the distribution and correlation of peneplain and the related morphological features, the extent and intensity of tectonic move- ments influencing the crossing of climatic thresholds, leading to terrace development, need to be studied further.
Insulin regulates liver metabolism in vivo in the absence of hepatic Akt and Foxo1
The insulin signaling pathway regulating glucose homeostasis that has been well accepted is insulin-to-insulin receptor-to-IRS proteins-to-PI3K-to-Akt-to-Foxo1—a pathway that does not respond properly in states of insulin resistance, including type 2 diabetes. In a new study from Morris Birnbaum and colleagues, an alternative insulin signaling pathway has been uncovered, as mice with liver-specific deletion of Akt and Foxo1 still respond normally to nutritional cues and properly regulate glucose metabolism. Although the exact nature of this alternative pathway needs to be identified, the results should open many new avenues of exploration in the field of type 2 diabetes. Considerable data support the idea that forkhead box O1 (Foxo1) drives the liver transcriptional program during fasting and is then inhibited by thymoma viral proto-oncogene 1 (Akt) after feeding. Here we show that mice with hepatic deletion of Akt1 and Akt2 were glucose intolerant, insulin resistant and defective in their transcriptional response to feeding in the liver. These defects were normalized with concomitant liver-specific deletion of Foxo1 . Notably, in the absence of both Akt and Foxo1, mice adapted appropriately to both the fasted and fed state, and insulin suppressed hepatic glucose production normally. A gene expression analysis revealed that deletion of Akt in liver led to the constitutive activation of Foxo1-dependent gene expression, but again, concomitant ablation of Foxo1 restored postprandial regulation, preventing the inhibition of the metabolic response to nutrient intake caused by deletion of Akt . These results are inconsistent with the canonical model of hepatic metabolism in which Akt is an obligate intermediate for proper insulin signaling. Rather, they show that a major role of hepatic Akt is to restrain the activity of Foxo1 and that in the absence of Foxo1, Akt is largely dispensable for insulin- and nutrient-mediated hepatic metabolic regulation in vivo .
Ptr-miR397a is a negative regulator of laccase genes affecting lignin content in Populus trichocarpa
Laccases, as early as 1959, were proposed to catalyze the oxidative polymerization of monolignols. Genetic evidence in support of this hypothesis has been elusive due to functional redundancy of laccase genes. An Arabidopsis double mutant demonstrated the involvement of laccases in lignin biosynthesis. We previously identified a subset of laccase genes to be targets of a microRNA (miRNA) ptr-miR397a in Populus trichocarpa . To elucidate the roles of ptr-miR397a and its targets, we characterized the laccase gene family and identified 49 laccase gene models, of which 29 were predicted to be targets of ptr-miR397a. We overexpressed Ptr-MIR397a in transgenic P. trichocarpa . In each of all nine transgenic lines tested, 17 PtrLAC s were down-regulated as analyzed by RNA-seq. Transgenic lines with severe reduction in the expression of these laccase genes resulted in an ∼40% decrease in the total laccase activity. Overexpression of Ptr-MIR397a in these transgenic lines also reduced lignin content, whereas levels of all monolignol biosynthetic gene transcripts remained unchanged. A hierarchical genetic regulatory network (GRN) built by a bottom-up graphic Gaussian model algorithm provides additional support for a role of ptr-miR397a as a negative regulator of laccases for lignin biosynthesis. Full transcriptome–based differential gene expression in the overexpressed transgenics and protein domain analyses implicate previously unidentified transcription factors and their targets in an extended hierarchical GRN including ptr-miR397a and laccases that coregulate lignin biosynthesis in wood formation. Ptr-miR397a, laccases, and other regulatory components of this network may provide additional strategies for genetic manipulation of lignin content.
Genome editing of a rice CDP-DAG synthase confers multipathogen resistance
The discovery and application of genome editing introduced a new era of plant breeding by giving researchers efficient tools for the precise engineering of crop genomes1. Here we demonstrate the power of genome editing for engineering broad-spectrum disease resistance in rice (Oryza sativa). We first isolated a lesion mimic mutant (LMM) from a mutagenized rice population. We then demonstrated that a 29-base-pair deletion in a gene we named RESISTANCE TO BLAST1 (RBL1) caused broad-spectrum disease resistance and showed that this mutation caused an approximately 20-fold reduction in yield. RBL1 encodes a cytidine diphosphate diacylglycerol synthase that is required for phospholipid biosynthesis2. Mutation of RBL1 results in reduced levels of phosphatidylinositol and its derivative phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). In rice, PtdIns(4,5)P2 is enriched in cellular structures that are specifically associated with effector secretion and fungal infection, suggesting that it has a role as a disease-susceptibility factor3. By using targeted genome editing, we obtained an allele of RBL1, named RBL1Δ12, which confers broad-spectrum disease resistance but does not decrease yield in a model rice variety, as assessed in small-scale field trials. Our study has demonstrated the benefits of editing an LMM gene, a strategy relevant to diverse LMM genes and crops.
Effective combinatorial immunotherapy for penile squamous cell carcinoma
Penile squamous cell carcinoma (PSCC) accounts for over 95% of penile malignancies and causes significant mortality and morbidity in developing countries. Molecular mechanisms and therapies of PSCC are understudied, owing to scarcity of laboratory models. Herein, we describe a genetically engineered mouse model of PSCC, by co-deletion of Smad4 and Apc in the androgen-responsive epithelium of the penis. Mouse PSCC fosters an immunosuppressive microenvironment with myeloid-derived suppressor cells (MDSCs) as a dominant population. Preclinical trials in the model demonstrate synergistic efficacy of immune checkpoint blockade with the MDSC-diminishing drugs cabozantinib or celecoxib. A critical clinical problem of PSCC is chemoresistance to cisplatin, which is induced by Pten deficiency on the backdrop of Smad4/Ap c co-deletion. Drug screen studies informed by targeted proteomics identify a few potential therapeutic strategies for PSCC. Our studies have established what we believe to be essential resources for studying PSCC biology and developing therapeutic strategies. Penile squamous cell carcinoma (PSCC) is a cancer that is associated with significant mortality. Here, the authors develop a mouse model of PSCC by co-deletion of Smad4 and Apc in the androgen-responsive penile epithelium, and show synergistic efficacy of checkpoint therapy with cabozantinib or celecoxib in their model.
Effective combinatorial immunotherapy for castration-resistant prostate cancer
A new chimaeric mouse model of metastatic castration-resistant prostate cancer to efficiently test combination therapies in an autochthonous setting. Combination cancer therapies Metastatic castration-resistant prostate cancer (mCRPC) does not show strong responses to immunotherapies, such as immune checkpoint blockade (ICB), which have produced durable therapeutic responses in other cancer types. The authors develop a new chimaeric mouse model of mCRPC in which they test different combinations of immunotherapies, including ICB, and targeted therapies. They found that the most efficacious combinations were those that depleted myeloid-derived suppressor cells, suggesting the potential clinical relevance of this cell population. A significant fraction of patients with advanced prostate cancer treated with androgen deprivation therapy experience relapse with relentless progression to lethal metastatic castration-resistant prostate cancer (mCRPC) 1 . Immune checkpoint blockade using antibodies against cytotoxic-T-lymphocyte-associated protein 4 (CTLA4) or programmed cell death 1/programmed cell death 1 ligand 1 (PD1/PD-L1) generates durable therapeutic responses in a significant subset of patients across a variety of cancer types 2 . However, mCRPC showed overwhelming de novo resistance to immune checkpoint blockade 3 , 4 , 5 , motivating a search for targeted therapies that overcome this resistance. Myeloid-derived suppressor cells (MDSCs) are known to play important roles in tumour immune evasion 6 . The abundance of circulating MDSCs correlates with prostate-specific antigen levels and metastasis in patients with prostate cancer 7 , 8 , 9 . Mouse models of prostate cancer show that MDSCs (CD11b + Gr1 + ) promote tumour initiation 10 and progression 11 . These observations prompted us to hypothesize that robust immunotherapy responses in mCRPC may be elicited by the combined actions of immune checkpoint blockade agents together with targeted agents that neutralize MDSCs yet preserve T-cell function. Here we develop a novel chimaeric mouse model of mCRPC to efficiently test combination therapies in an autochthonous setting. Combination of anti-CTLA4 and anti-PD1 engendered only modest efficacy. Targeted therapy against mCRPC-infiltrating MDSCs, using multikinase inhibitors such as cabozantinib and BEZ235, also showed minimal anti-tumour activities. Strikingly, primary and metastatic CRPC showed robust synergistic responses when immune checkpoint blockade was combined with MDSC-targeted therapy. Mechanistically, combination therapy efficacy stemmed from the upregulation of interleukin-1 receptor antagonist and suppression of MDSC-promoting cytokines secreted by prostate cancer cells. These observations illuminate a clinical path hypothesis for combining immune checkpoint blockade with MDSC-targeted therapies in the treatment of mCRPC.
Sustained methane emissions from China after 2012 despite declining coal production and rice-cultivated area
China’s anthropogenic methane emissions are the largest of any country in the world. A recent study using atmospheric observations suggested that recent policies aimed at reducing emissions of methane due to coal production in China after 2010 had been largely ineffective. Here, based on a longer observational record and an updated modelling approach, we find a statistically significant positive linear trend (0.36 ± 0.04 ( ± 1 σ ) Tg CH 4 yr −2 ) in China’s methane emissions for 2010–2017. This trend was slowing down at a statistically significant rate of -0.1 ± 0.04 Tg CH 4 yr −3 . We find that this decrease in growth rate can in part be attributed to a decline in China’s coal production. However, coal mine methane emissions have not declined as rapidly as production, implying that there may be substantial fugitive emissions from abandoned coal mines that have previously been overlooked. We also find that emissions over rice-growing and aquaculture-farming regions show a positive trend (0.13 ± 0.05 Tg CH 4 yr −2 for 2010–2017) despite reports of shrinking rice paddy areas, implying potentially significant emissions from new aquaculture activities, which are thought to be primarily located on converted rice paddies.
Materials informatics
Materials informatics employs techniques, tools, and theories drawn from the emerging fields of data science, internet, computer science and engineering, and digital technologies to the materials science and engineering to accelerate materials, products and manufacturing innovations. Manufacturing is transforming into shorter design cycles, mass customization, on-demand production, and sustainable products. Additive manufacturing or 3D printing is a popular example of such a trend. However, the success of this manufacturing transformation is critically dependent on the availability of suitable materials and of data on invertible processing–structure–property–performance life cycle linkages of materials. Experience suggests that the material development cycle, i.e. the time to develop and deploy new material, generally exceeds the product design and development cycle. Hence, there is a need to accelerate materials innovation in order to keep up with product and manufacturing innovations. This is a major challenge considering the hundreds of thousands of materials and processes, and the huge amount of data on microstructure, composition, properties, and functional, environmental, and economic performance of materials. Moreover, the data sharing culture among the materials community is sparse. Materials informatics is key to the necessary transformation in product design and manufacturing. Through the association of material and information sciences, the emerging field of materials informatics proposes to computationally mine and analyze large ensembles of experimental and modeling datasets efficiently and cost effectively and to deliver core materials knowledge in user-friendly ways to the designers of materials and products, and to the manufacturers. This paper reviews the various developments in materials informatics and how it facilitates materials innovation by way of specific examples.
A histone deacetylase 3–dependent pathway delimits peripheral myelin growth and functional regeneration
Screening for small-molecule epigenetic modulators identifies HDAC3 inhibitors that promote peripheral myelin repair after nerve injury in rodents. Deficits in Schwann cell–mediated remyelination impair functional restoration after nerve damage, contributing to peripheral neuropathies. The mechanisms mediating block of remyelination remain elusive. Here, through small-molecule screening focusing on epigenetic modulators, we identified histone deacetylase 3 (HDAC3; a histone-modifying enzyme) as a potent inhibitor of peripheral myelinogenesis. Inhibition of HDAC3 enhanced myelin growth and regeneration and improved functional recovery after peripheral nerve injury in mice. HDAC3 antagonizes the myelinogenic neuregulin–PI3K–AKT signaling axis. Moreover, genome-wide profiling analyses revealed that HDAC3 represses promyelinating programs through epigenetic silencing while coordinating with p300 histone acetyltransferase to activate myelination-inhibitory programs that include the HIPPO signaling effector TEAD4 to inhibit myelin growth. Schwann cell–specific deletion of either Hdac3 or Tead4 in mice resulted in an elevation of myelin thickness in sciatic nerves. Thus, our findings identify the HDAC3–TEAD4 network as a dual-function switch of cell-intrinsic inhibitory machinery that counters myelinogenic signals and maintains peripheral myelin homeostasis, highlighting the therapeutic potential of transient HDAC3 inhibition for improving peripheral myelin repair.