An updated model of shoot apical meristem regulation by ERECTA family and CLAVATA3 signaling pathways in Arabidopsis.

The shoot apical meristem (SAM) gives rise to the aboveground organs of plants. The size of the SAM is relatively constant due to the balance between stem cell replenishment and cell recruitment into new organs. In angiosperms, the transcription factor WUSCHEL (WUS) promotes stem cell proliferation in the central zone of the SAM. WUS forms a negative feedback loop with a signaling pathway activated by CLAVATA3 (CLV3). In the periphery of the SAM, the ERECTA family receptors (ERfs) constrain WUS and CLV3 expression. Here, we show that four ligands of ERfs redundantly inhibit the expression of these two genes. Transcriptome analysis confirmed that WUS and CLV3 are the main targets of ERf signaling and uncovered new ones. Analysis of promoter reporters indicated that the WUS expression domain mostly overlaps with the CLV3 domain and does not shift along the apical-basal axis in clv3 mutants. Our three-dimensional mathematical model captured gene expression distributions at the single-cell level under various perturbed conditions. Based on our findings, CLV3 regulates cellular levels of WUS mostly through autocrine signaling, and ERfs regulate the spatial expression of WUS, preventing its encroachment into the peripheral zone.

Data- and theory-driven approaches for understanding paths of epithelial-mesenchymal transition.

Reversible transitions between epithelial and mesenchymal cell states are a crucial form of epithelial plasticity for development and disease progression. Recent experimental data and mechanistic models showed multiple intermediate epithelial-mesenchymal transition (EMT) states as well as trajectories of EMT underpinned by complex gene regulatory networks. In this review, we summarize recent progress in quantifying EMT and characterizing EMT paths with computational methods and quantitative experiments including omics-level measurements. We provide perspectives on how these studies can help relating fundamental cell biology to physiological and pathological outcomes of EMT.

Twenty Years of Epithelial-Mesenchymal Transition: A State of the Field from TEMTIA X.

This report summarizes the 10th biennial meeting of The Epithelial Mesenchymal Transition International Association (TEMTIA), that took place in Paris on November 7-10, 2022. It provides a short but comprehensive introduction to the presentations and discussions that took place during the 3-day meeting. Similarly to previous TEMTIA meetings, TEMTIA X reviewed the most recent aspects of the epithelial-mesenchymal transition (EMT), a cellular process involved during distinct stages of development but also during wound healing and fibrosis to some degree. EMT has also been associated at various levels during tumor cell progression and metastasis. The meeting emphasized the intermediate stages of EMT (partial EMT or EM hybrid cells) involved in the malignant process and their potential physiological or pathological importance, taking advantage of advancements in molecular methods at the single-cell level. It also introduced novel descriptions of EMT occurrences during early embryogenesis. Sessions explored relationships between EMT and cell metabolism and how EMT can affect immune responses, particularly during tumor progression, providing new targets for cancer therapy. Finally, it introduced a new perception of EMT biological meaning based on an evolutionary perspective. The meeting integrated the TEMTIA general assembly, allowing general discussion about the future of the association and the site of the next meeting, now decided to take place in Seattle, USA, in November 2024. This report provides a comprehensive introduction to the presentations and discussions that took place during the 10th biennial meeting of TEMTIA, that occurred in Paris on November 7-10, 2022. It includes all the sessions and follows the chronological order during the 3-day meeting. A general purpose of the meeting was to explore the boundaries of the EMT process, including new concepts and developments, as illustrated by our leitmotiv for the meeting, inspired by the proximity of the Cluny Museum in Paris.

Impact of cesarean section on metabolic syndrome components in offspring rats.

INTRODUCTION: Epidemiological evidence suggests an association between CS and offspring metabolic syndrome (MetS), but whether a causal relationship exists is unknown. METHODS: In this study, timed-mated Wistar rat dams were randomly assigned to cesarean section (CS), vaginal delivery (VD), and surrogate groups. The offspring from both CS and VD groups were reared by surrogate dams until weaning, and weaned male offspring from both groups were randomly assigned to receive normal diet (ND) or high-fat/high-fructose diet (HFF) ad libitum for 39 weeks. RESULTS: By the end of study, CS-ND offspring gained 17.8% more weight than VD-ND offspring, while CS-HFF offspring gained 36.4% more weight than VD-HFF offspring. Compared with VD-ND offspring, CS-ND offspring tended to have increased triglycerides (0.27 mmol/l, 95% CI, 0.05 to 0.50), total cholesterol (0.30 mmol/l, -0.08 to 0.68), and fasting plasma glucose (FPG) (0.30 mmol/l, -0.01 to 0.60); more pronounced differences were observed between CS-HFF and VD-HFF offspring in these indicators (triglyceride, 0.66 mmol/l, 0.35 to 0.97; total cholesterol, 0.46 mmol/l, 0.13 to 0.79; and FPG, 0.55 mmol/l, 0.13 to 0.98). CONCLUSIONS: CS offspring were more prone to adverse metabolic profile and HFF might exacerbate this condition, indicating the association between CS and MetS is likely to be causal. IMPACT: Whether the observed associations between CS and MetS in non-randomized human studies are causally relevant remains undetermined. Compared with vaginally born offspring rats, CS born offspring gained more body weight and tended to have compromised lipid profiles and abnormal insulin sensitivity, suggesting a causal relationship between CS and MetS that may be further amplified by a high-fat/high-fructose diet. Due to the high prevalence of CS births globally, greater clinical consideration must be given to the potential adverse effects of CS, and whether these risks should be made known to patients in clinical practice merits evaluation.

Arp2/3-dependent endocytosis ensures Cdc42 oscillations by removing Pak1-mediated negative feedback.

The GTPase Cdc42 regulates polarized growth in most eukaryotes. In the bipolar yeast Schizosaccharomyces pombe, Cdc42 activation cycles periodically at sites of polarized growth. These periodic cycles are caused by alternating positive feedback and time-delayed negative feedback loops. At each polarized end, negative feedback is established when active Cdc42 recruits the Pak1 kinase to prevent further Cdc42 activation. It is unclear how Cdc42 activation returns to each end after Pak1-dependent negative feedback. We find that disrupting branched actin-mediated endocytosis disables Cdc42 reactivation at the cell ends. Using experimental and mathematical approaches, we show that endocytosis-dependent Pak1 removal from the cell ends allows the Cdc42 activator Scd1 to return to that end to enable reactivation of Cdc42. Moreover, we show that Pak1 elicits its own removal via activation of endocytosis. These findings provide a deeper insight into the self-organization of Cdc42 regulation and reveal previously unknown feedback with endocytosis in the establishment of cell polarity.

Structural basis of negative regulation of CRISPR-Cas7-11 by TPR-CHAT.

CRISPR‒Cas7-11 is a Type III-E CRISPR-associated nuclease that functions as a potent RNA editing tool. Tetratrico-peptide repeat fused with Cas/HEF1-associated signal transducer (TPR-CHAT) acts as a regulatory protein that interacts with CRISPR RNA (crRNA)-bound Cas7-11 to form a CRISPR-guided caspase complex (Craspase). However, the precise modulation of Cas7-11's nuclease activity by TPR-CHAT to enhance its utility requires further study. Here, we report cryo-electron microscopy (cryo-EM) structures of Desulfonema ishimotonii (Di) Cas7-11-crRNA, complexed with or without the full length or the N-terminus of TPR-CHAT. These structures unveil the molecular features of the Craspase complex. Structural analysis, combined with in vitro nuclease assay and electrophoretic mobility shift assay, reveals that DiTPR-CHAT negatively regulates the activity of DiCas7-11 by preventing target RNA from binding through the N-terminal 65 amino acids of DiTPR-CHAT (DiTPR-CHATNTD). Our work demonstrates that DiTPR-CHATNTD can function as a small unit of DiCas7-11 regulator, potentially enabling safe applications to prevent overcutting and off-target effects of the CRISPR‒Cas7-11 system.

Hematoporphyrin derivative-mediated photodynamic techniques for the diagnosis and treatment of chordoma.

BACKGROUND: Chordoma is a rare congenital low-grade malignant tumor characterized by infiltrative growth. It often tends to compress important intracranial nerves and blood vessels, making its surgical treatment extremely difficult. Besides, the efficacy of radiotherapy and chemotherapy is limited. The photosensitizer hematoporphyrin derivative (HPD) can emit red fluorescence under 405 nm excitation and produce reactive oxygen species for tumor therapy under 630 nm excitation. Herein, we investigated the effects of the photosensitizer hematoporphyrin derivative (HPD) on different cell lines of chordoma and xenograft tumors under 405 nm and 630 nm excitation. METHODS: The photosensitizer hematoporphyrin derivative (HPD) and Two different chordoma cell lines (U-CH1, JHC7) were used for the test. The in vitro experiments were as follows: (1) the fluorescence intensity emitted by chordoma cells excited by different 405 nm light intensities was observed under a confocal microscope; (2) the Cell Counting Kit-8 (CCK-8) assay was performed to detect the effects of different photosensitizer concentrations and 630 nm light energy densities on the activity of chordoma cells. In the in vivo experiments, (3) Fluorescence visualization of chordoma xenograft tumors injected with photosensitizer via tail vein under 405 nm excitation; (4) Impact of 630 nm excitation of photosensitizer on the growth of chordoma xenograft tumors. RESULTS: (1) The photosensitizers in chordoma cells and chordoma xenografts of nude mice were excited by 405 nm to emit red fluorescence; (2) 630 nm excitation photosensitizer reduces chordoma cell activity and inhibits chordoma xenograft tumor growth in chordoma nude mice. CONCLUSION: Photodynamic techniques mediated by the photosensitizer hematoporphyrin derivatives can be used for the diagnosis and treatment of chordoma.

Comparing the severity of second preeclampsia with first preeclampsia: a multicenter retrospective longitudinal cohort study.

OBJECTIVE: Compare the clinical severity of second preeclampsia with the first preeclampsia. METHODS: This retrospective longitudinal cohort study was conducted in three teaching hospitals in Guangzhou, where there were a total of 296 405 deliveries between 2010 and 2021. Two consecutive singleton deliveries complicated with preeclampsia were included. Clinical features, laboratory results within 1 week before delivery, and maternal and neonatal outcomes of both deliveries were collected. Univariate analyses were made using paired Wilcoxon tests and McNemar tests. Multivariable logistic regression and generalized linear models were performed to assess the association of adverse maternal and neonatal outcomes with second preeclampsia. RESULTS: A total of 151 women were included in the study. The mean maternal age was 28 and 33 years for the first and second deliveries, respectively. The proportion of preventive acetylsalicylic acid use was 4.6% for the first delivery and 15.2% for the second delivery. No significant differences were observed in terms of blood pressure on admission, gestational weeks of admission and delivery, application of perinatal antihypertensive agents, rates of preterm delivery, and severe features between the two occurrences. However, the rates of heart disease, edema, and admission to the ICU were lower, and hospital stays were shorter in the second preeclampsia compared with the first preeclampsia. Sensitivity analysis conducted among women who did not use preventive acetylsalicylic acid yielded similar results. After adjusting for potential confounding variables, the occurrence of second preeclampsia was associated with significantly decreased risks of heart disease, edema, complications, and admission to the NICU, with odds ratios ranging between 0.157 and 0.336. CONCLUSION: Contrary to expectations, the second preeclampsia did not exhibit worse manifestations or outcomes to the first occurrence. In fact, some clinical features and outcomes appeared to be better in the second preeclampsia.

The Arp2/3 complex promotes periodic removal of Pak1-mediated negative feedback to facilitate anticorrelated Cdc42 oscillations.

The conserved GTPase Cdc42 is a major regulator of polarized growth in most eukaryotes. Cdc42 periodically cycles between active and inactive states at sites of polarized growth. These periodic cycles are caused by positive feedback and time-delayed negative feedback loops. In the bipolar yeast S. pombe, both growing ends must regulate Cdc42 activity. At each cell end, Cdc42 activity recruits the Pak1 kinase which prevents further Cdc42 activation thus establishing negative feedback. It is unclear how Cdc42 activation returns to the end after Pak1-dependent negative feedback. Using genetic and chemical perturbations, we find that disrupting branched actin-mediated endocytosis disables Cdc42 reactivation at the cell ends. With our experimental data and mathematical models, we show that endocytosis-dependent Pak1 removal from the cell ends allows the Cdc42 activator Scd1 to return to that end to enable reactivation of Cdc42. Moreover, we show that Pak1 elicits its own removal via activation of endocytosis. In agreement with these observations, our model and experimental data show that in each oscillatory cycle, Cdc42 activation increases followed by an increase in Pak1 recruitment at that end. These findings provide a deeper insight into the self-organization of Cdc42 regulation and reveal previously unknown feedback with endocytosis in the establishment of cell polarity.