A wall with integrity Rui, Yue; Dinneny, José R.
The New phytologist,
02/2020, Letnik:
225, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The structural and functional integrity of the cell wall needs to be constantly monitored and fine-tuned to allow for growth while preventing mechanical failure. Many studies have advanced our ...understanding of the pathways that contribute to cell wall biosynthesis and how these pathways are regulated by external and internal cues. Recent evidence also supports a model in which certain aspects of the wall itself may act as growth-regulating signals. Molecular components of the signaling pathways that sense and maintain cell wall integrity have begun to be revealed, including signals arising in the wall, sensors that detect changes at the cell surface, and downstream signal transduction modules. Abiotic and biotic stress conditions provide new contexts for the study of cell wall integrity, but the nature and consequences of wall disruptions due to various stressors require further investigation. A deeper understanding of cell wall signaling will provide insights into the growth regulatory mechanisms that allow plants to survive in changing environments.
Bone marrow stromal cells maintain the adult skeleton by forming osteoblasts throughout life that regenerate bone and repair fractures. We discovered that subsets of these stromal cells, osteoblasts, ...osteocytes, and hypertrophic chondrocytes secrete a C-type lectin domain protein, Clec11a, which promotes osteogenesis.
-deficient mice appeared developmentally normal and had normal hematopoiesis but reduced limb and vertebral bone.
-deficient mice exhibited accelerated bone loss during aging, reduced bone strength, and delayed fracture healing. Bone marrow stromal cells from
-deficient mice showed impaired osteogenic differentiation, but normal adipogenic and chondrogenic differentiation. Recombinant Clec11a promoted osteogenesis by stromal cells in culture and increased bone mass in osteoporotic mice in vivo. Recombinant human Clec11a promoted osteogenesis by human bone marrow stromal cells in culture and in vivo. Clec11a thus maintains the adult skeleton by promoting the differentiation of mesenchymal progenitors into mature osteoblasts. In light of this, we propose to call this factor Osteolectin.
Plant cell separation and expansion require pectin degradation by endogenous pectinases such as polygalacturonases, few of which have been functionally characterized. Stomata are a unique system to ...study both processes because stomatal maturation involves limited separation between sister guard cells and stomatal responses require reversible guard cell elongation and contraction. However, the molecular mechanisms for how stomatal pores form and how guard cell walls facilitate dynamic stomatal responses remain poorly understood. We characterized POLYGALACTURONASE INVOLVED IN EXPANSION3 (PGX3), which is expressed in expanding tissues and guard cells. PGX3-GFP localizes to the cell wall and is enriched at sites of stomatal pore initiation in cotyledons. In seedlings, ablating or overexpressing PGX3 affects both cotyledon shape and the spacing and pore dimensions of developing stomata. In adult plants, PGX3 affects rosette size. Although stomata in true leaves display normal density and morphology when PGX3 expression is altered, loss of PGX3 prevents smooth stomatal closure, and overexpression of PGX3 accelerates stomatal opening. These phenotypes correspond with changes in pectin molecular mass and abundance that can affect wall mechanics. Together, these results demonstrate that PGX3-mediated pectin degradation affects stomatal development in cotyledons, promotes rosette expansion, and modulates guard cell mechanics in adult plants.
Cuspy shadow was first reported for hairy rotating black holes, whose metrics deviate significantly from the Kerr one. The non-smooth edge of the shadow is attributed to a transition between ...different branches of unstable but bounded orbits, known as the fundamental photon orbits, which end up at the light rings. In searching for a minimal theoretical setup to reproduce such a salient feature, in this work, we devise a toy model with axisymmetry, a slowly rotating Kerr black hole enveloped by a thin slowly rotating dark matter shell. Despite its simplicity, we show rich structures regarding fundamental photon orbits explicitly in such a system. We observe two disconnected branches of unstable spherical photon orbits, and the jump between them gives rise to a pair of cusps in the resultant black hole shadow. Besides the cuspy shadow, we explore other intriguing phenomena when the Maxwell construction cannot be established. We find that it is possible to have an incomplete arc of Einstein rings and a “fractured” shadow. The potential astrophysical significance of the corresponding findings is addressed.
Endothelial cells and leptin receptor
(LepR
) stromal cells are critical sources of haematopoietic stem cell (HSC) niche factors, including stem cell factor (SCF), in bone marrow. After irradiation ...or chemotherapy, these cells are depleted while adipocytes become abundant. We discovered that bone marrow adipocytes synthesize SCF. They arise from Adipoq-Cre/ER
progenitors, which represent ∼5% of LepR
cells, and proliferate after irradiation. Scf deletion using Adipoq-Cre/ER inhibited haematopoietic regeneration after irradiation or 5-fluorouracil treatment, depleting HSCs and reducing mouse survival. Scf from LepR
cells, but not endothelial, haematopoietic or osteoblastic cells, also promoted regeneration. In non-irradiated mice, Scf deletion using Adipoq-Cre/ER did not affect HSC frequency in long bones, which have few adipocytes, but depleted HSCs in tail vertebrae, which have abundant adipocytes. A-ZIP/F1 'fatless' mice exhibited delayed haematopoietic regeneration in long bones but not in tail vertebrae, where adipocytes inhibited vascularization. Adipocytes are a niche component that promotes haematopoietic regeneration.
Studies of the identity and physiological function of mesenchymal stromal cells (MSCs) have been hampered by a lack of markers that permit both prospective identification and fate mapping in vivo. We ...found that Leptin Receptor (LepR) is a marker that highly enriches bone marrow MSCs. Approximately 0.3% of bone marrow cells were LepR+, 10% of which were CFU-Fs, accounting for 94% of bone marrow CFU-Fs. LepR+ cells formed bone, cartilage, and adipocytes in culture and upon transplantation in vivo. LepR+ cells were Scf-GFP+, Cxcl12-DsRedhigh, and Nestin-GFPlow, markers which also highly enriched CFU-Fs, but negative for Nestin-CreER and NG2-CreER, markers which were unlikely to be found in CFU-Fs. Fate-mapping showed that LepR+ cells arose postnatally and gave rise to most bone and adipocytes formed in adult bone marrow, including bone regenerated after irradiation or fracture. LepR+ cells were quiescent, but they proliferated after injury. Therefore, LepR+ cells are the major source of bone and adipocytes in adult bone marrow.
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•LepR+ cells account for 0.3% of cells and 94% of CFU-Fs in adult bone marrow•LepR+ cells form osteoblasts, chondrocytes, and adipocytes in culture and in vivo•LepR+ cells give rise to most of the bone and adipocytes formed in adult marrow•LepR+ cells are normally quiescent but proliferate after injury to regenerate bone
Zhou et al. reveal that cells positive for Leptin receptor (LepR) are the main source of mesenchymal stromal cells (MSCs), bone-forming progenitors, and adipocytes in adult mouse bone marrow.
Stomatal guard cells are pairs of specialized epidermal cells that control water and CO₂ exchange between the plant and the environment. To fulfill the functions of stomatal opening and closure that ...are driven by changes in turgor pressure, guard cell walls must be both strong and flexible, but how the structure and dynamics of guard cell walls enable stomatal function remains poorly understood. To address this question, we applied cell biological and genetic analyses to investigate guard cell walls and their relationship to stomatal function in Arabidopsis (Arabidopsis thaliana). Using live-cell spinning disk confocal microscopy, we measured the motility of cellulose synthase (CESA)-containing complexes labeled by green fluorescent protein (GFP)-CESA3 and observed a reduced proportion of GFP-CESA3 particles colocalizing with microtubules upon stomatal closure. Imaging cellulose organization in guard cells revealed a relatively uniform distribution of cellulose in the open state and a more fibrillar pattern in the closed state, indicating that cellulose microfibrils undergo dynamic reorganization during stomatal movements. In cesa3je5
mutants defective in cellulose synthesis and xxt1 xxt2 mutants lacking the hemicellulose xyloglucan, stomatal apertures, changes in guard cell length, and cellulose reorganization were aberrant during fusicoccin-induced stomatal opening or abscisic acid-induced stomatal closure, indicating that sufficient cellulose and xyloglucan are required for normal guard cell dynamics. Together, these results provide new insights into how guard cell walls allow stomata to function as responsive mediators of gas exchange at the plant surface.
Colorectal cancer (CRC) is one of the most common types of malignant tumor. Many genetic factors have been proved to show high association with the occurrence and development of CRC and many ...mutations are detected in CRC. PTPN4/PTP‐MEG1 is a widely expressed non–receptor protein tyrosine phosphatase. Over the past three decades, PTPN4 has been demonstrated in the literature to participate in many biological processes. In this study, we identified a nonsense mutation of PTPN4 with a mutation ratio of 90.90% from 1 case of rectal cancer, leading to loss of function in PTPN4 gene. Several somatic mutations occurred in 5/137 rectal cancer samples from The Cancer Genome Atlas Rectum Adenocarcinoma (TCGA READ) database. Interestingly, we found that PTPN4 negative cytoplasm staining was more prone to lymphatic metastasis (N = 50, P = 0.0153) and low expression of PTPN4 in rectal cancer was highly associated with poor prognosis. Overexpression of PTPN4 suppressed the cell growth, and moreover, the loss of PTPN4 accelerated cell growth and boosted clonogenicity of CRC cells. Furthermore, we revealed that the deletion of PTPN4 promoted the tumor formation of NCM460 cells in vivo. In terms of the molecular mechanism, we demonstrated that PTPN4 dephosphorylates pSTAT3 at the Tyr705 residue with a direct interaction and suppresses the transcriptional activity of STAT3. In summary, our study revealed a novel mechanism that the tumorigenesis of colorectal cancer might be caused by the loss of PTPN4 through activating STAT3, which will broaden the therapy strategy for anti–rectal cancer in the future.
In our study, we identified a nonsense mutation of PTPN4 with mutation ratio of 90.90% from 1 case of rectal cancer. Overexpression of PTPN4 suppressed the growth of colorectal cancer cells. PTPN4 dephosphorylates pSTAT3 at the Tyr705 residue with a direct interaction and depresses the transcriptional activity of STAT3.
Single-cell RNA sequencing (scRNA-seq) technologies are poised to reshape the current cell-type classification system. However, a transcriptome-based single-cell atlas has not been achieved for ...complex mammalian systems. Here, we developed Microwell-seq, a high-throughput and low-cost scRNA-seq platform using simple, inexpensive devices. Using Microwell-seq, we analyzed more than 400,000 single cells covering all of the major mouse organs and constructed a basic scheme for a mouse cell atlas (MCA). We reveal a single-cell hierarchy for many tissues that have not been well characterized previously. We built a web-based “single-cell MCA analysis” pipeline that accurately defines cell types based on single-cell digital expression. Our study demonstrates the wide applicability of the Microwell-seq technology and MCA resource.
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•Development of Microwell-seq, a high-throughput and low-cost scRNA-seq platform•Construction of a single-cell mouse cell atlas (scMCA) covering major cell types•Characterization of cellular heterogeneity with minimal batch effect•Characterization of cross-tissue cellular network at the single-cell level
Development of Microwell-seq allows construction of a mouse cell atlas at the single-cell level with a high-throughput and low-cost platform.
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