Browsing by Issue Date, starting with "2020"
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- A Tgfbr1/Snai1-dependent developmental module at the core of vertebrate axial elongationPublication . Dias, André; Lozovska, Anastasiia; Wymeersch, Filip J; Nóvoa, Ana; Binagui-Casas, Anahi; Sobral, Daniel; Martins, Gabriel G; Wilson, Valerie; Mallo, Moises
- Patterning and Morphogenesis From Cells to Organisms: Progress, Common Principles and New ChallengesPublication . Goryachev, Andrew B.; Mallo, Moisés
- Plasma membrane H+-ATPases sustain pollen tube growth and fertilizationPublication . Hoffmann, Robert D.; Portes, Maria Teresa; Olsen, Lene Irene; Damineli, Daniel Santa Cruz; Hayashi, Maki; Nunes, Custódio O.; Pedersen, Jesper T.; Lima, Pedro T.; Campos, Cláudia; Feijó, José A.; Palmgren, MichaelPollen tubes are highly polarized tip-growing cells that depend on cytosolic pH gradients for signaling and growth. Autoinhibited plasma membrane proton (H+) ATPases (AHAs) have been proposed to energize pollen tube growth and underlie cell polarity, however, mechanistic evidence for this is lacking. Here we report that the combined loss of AHA6, AHA8, and AHA9 in Arabidopsis thaliana delays pollen germination and causes pollen tube growth defects, leading to drastically reduced fertility. Pollen tubes of aha mutants had reduced extracellular proton (H+) and anion fluxes, reduced cytosolic pH, reduced tip-to-shank proton gradients, and defects in actin organization. Furthermore, mutant pollen tubes had less negative membrane potentials, substantiating a mechanistic role for AHAs in pollen tube growth through plasma membrane hyperpolarization. Our findings define AHAs as energy transducers that sustain the ionic circuit defining the spatial and temporal profiles of cytosolic pH, thereby controlling downstream pH-dependent mechanisms essential for pollen tube elongation, and thus plant fertility.
- Asymmetric neurogenic commitment of retinal progenitors involves Notch through the endocytic pathwayPublication . Nerli, Elisa; Rocha-Martins, Mauricio; Norden, CarenDuring brain development, progenitor cells need to balanceproliferation and differentiation in order to generate different neurons in the correct numbers and proportions. Currently, the patterns of multipotent progenitor divisions that lead to neurogenic entry and the factors that regulate them are not fully understood. We here use the zebrafish retina to address this gap, exploiting its suitability for quantitative live-imaging. We show that early neurogenic progenitors arise from asymmetric divisions. Notch regulates this asymmetry, as when inhibited, symmetric divisions producing two neurogenic progenitors occur. Surprisingly however, Notch does not act through an apicobasal activity gradient as previously suggested, but through asymmetric inheritance of Sara-positive endosomes. Further, the resulting neurogenic progenitors show cell biological features different from multipotent progenitors, raising the possibility that an intermediate progenitor state exists in the retina. Our study thus reveals new insights into the regulation of proliferative and differentiative events during central nervous system development.
- Irgm2 and Gate‐16 cooperatively dampen Gram‐negative bacteria‐induced caspase‐11 responsePublication . Eren, Elif; Planès, Rémi; Bagayoko, Salimata; Bordignon, Pierre‐Jean; Chaoui, Karima; Hessel, Audrey; Santoni, Karin; Pinilla, Miriam; Lagrange, Brice; Burlet‐Schiltz, Odile; Howard, Jonathan C; Henry, Thomas; Yamamoto, Masahiro; Meunier, EtienneInflammatory caspase-11 (rodent) and caspases-4/5 (humans) detect the Gram-negative bacterial component LPS within the host cell cytosol, promoting activation of the non-canonical inflammasome. Although non-canonical inflammasome-induced pyroptosis and IL-1-related cytokine release are crucial to mount an efficient immune response against various bacteria, their unrestrained activation drives sepsis. This suggests that cellular components tightly control the threshold level of the non-canonical inflammasome in order to ensure efficient but non-deleterious inflammatory responses. Here, we show that the IFN-inducible protein Irgm2 and the ATG8 family member Gate-16 cooperatively counteract Gram-negative bacteria-induced non-canonical inflammasome activation, both in cultured macrophages and in vivo. Specifically, the Irgm2/Gate-16 axis dampens caspase-11 targeting to intracellular bacteria, which lowers caspase-11-mediated pyroptosis and cytokine release. Deficiency in Irgm2 or Gate16 induces both guanylate binding protein (GBP)-dependent and GBP-independent routes for caspase-11 targeting to intracellular bacteria. Our findings identify molecular effectors that fine-tune bacteria-activated non-canonical inflammasome responses and shed light on the understanding of the immune pathways they control.
- Deletion of iRhom2 protects against diet-induced obesity by increasing thermogenesisPublication . Badenes, Marina; Amin, Abdulbasit; González-García, Ismael; Félix, Inês; Burbridge, Emma; Cavadas, Miguel; Ortega, Francisco José; de Carvalho, Érika; Faísca, Pedro; Carobbio, Stefania; Seixas, Elsa; Pedroso, Dora; Neves-Costa, Ana; Moita, Luís F.; Fernández-Real, José Manuel; Vidal-Puig, António; Domingos, Ana; López, Miguel; Adrain, ColinObjective: Obesity is the result of positive energy balance. It can be caused by excessive energy consumption but also by decreased energy dissipation, which occurs under several conditions including when the development or activation of brown adipose tissue (BAT) is impaired. Here we evaluated whether iRhom2, the essential cofactor for the Tumour Necrosis Factor (TNF) sheddase ADAM17/TACE, plays a role in the pathophysiology of metabolic syndrome. Methods: We challenged WT versus iRhom2 KO mice to positive energy balance by chronic exposure to a high fat diet and then compared their metabolic phenotypes. We also carried out ex vivo assays with primary and immortalized mouse brown adipocytes to establish the autonomy of the effect of loss of iRhom2 on thermogenesis and respiration. Results: Deletion of iRhom2 protected mice from weight gain, dyslipidemia, adipose tissue inflammation, and hepatic steatosis and improved insulin sensitivity when challenged by a high fat diet. Crucially, the loss of iRhom2 promotes thermogenesis via BAT activation and beige adipocyte recruitment, enabling iRhom2 KO mice to dissipate excess energy more efficiently than WT animals. This effect on enhanced ther- mogenesis is cell-autonomous in brown adipocytes as iRhom2 KOs exhibit elevated UCP1 levels and increased mitochondrial proton leak.
- Isolated Incudostapedial Cholesteatomas: Unique Radiologic and Surgical FeaturesPublication . MacDonald, Bridget; Bommakanti, Krishna; Mallo, Moises; Carvalho, Daniela
- Methods for the Measurement of Early Events in Toxoplasma gondii Immunity in Mouse CellsPublication . Alvarez, Catalina; Campos, Ana Claudia; Howard, Jonathan C; Loureiro, Joana; Müller, Urs Benedikt; Rodrigues, Ana LinaCritical steps in resistance of mice against Toxoplasma gondii occur in the first 2 or 3 h after the pathogen has entered a cell that has been exposed to interferon γ (IFNγ). The newly formed parasitophorous vacuole is attacked by the IFNγ-inducible IRG proteins and disrupted, resulting in death of the parasite and necrotic death of the cell. Here we describe some techniques that we have used to describe and quantify these events in different combinations of the host and the parasite.
- Asymmetric neurogenic commitment of retinal progenitors is regulated via the Notch endocytic pathwayPublication . Nerli, Elisa; Rocha-Martins, Mauricio; Norden, Caren
- Klebsiella michiganensis transmission enhances resistance to Enterobacteriaceae gut invasion by nutrition competitionPublication . Oliveira, Rita A; Ng, Katharine M; Correia, Margarida B; Cabral, Vitor; Shi, Handuo; Sonnenburg, Justin L; Huang, Kerwyn Casey; Xavier, Karina BIntestinal microbiotas contain beneficial microorganisms that protect against pathogen colonization; treatment with antibiotics disrupts the microbiota and compromises colonization resistance. Here, we determine the impact of exchanging microorganisms between hosts on resilience to the colonization of invaders after antibiotic-induced dysbiosis. We assess the functional consequences of dysbiosis using a mouse model of colonization resistance against Escherichia coli. Antibiotics caused stochastic loss of members of the microbiota, but the microbiotas of co-housed mice remained more similar to each other compared with the microbiotas among singly housed animals. Strikingly, co-housed mice maintained colonization resistance after treatment with antibiotics, whereas most singly housed mice were susceptible to E. coli. The ability to retain or share the commensal Klebsiella michiganensis, a member of the Enterobacteriaceae family, was sufficient for colonization resistance after treatment with antibiotics. K. michiganensis generally outcompeted E. coli in vitro, but in vivo administration of galactitol-a nutrient that supports the growth of only E. coli-to bi-colonized gnotobiotic mice abolished the colonization-resistance capacity of K. michiganensis against E. coli, supporting the idea that nutrient competition is the primary interaction mechanism. K. michiganensis also hampered colonization of the pathogen Salmonella, prolonging host survival. Our results address functional consequences of the stochastic effects of microbiota perturbations, whereby microbial transmission through host interactions can facilitate reacquisition of beneficial commensals, minimizing the negative impact of antibiotics.