In vitro production of cat-restricted Toxoplasma pre-sexual stages

Sexual reproduction of Toxoplasma gondii, confined to the felid gut, remains largely uncharted owing to ethical concerns regarding the use of cats as model organisms. Chromatin modifiers dictate the developmental fate of the parasite during its multistage life cycle, but their targeting to stage-specific cistromes is poorly described$^{1,2}$. Here we found that the transcription factors AP2XII-1 and AP2XI-2 operate during the tachyzoite stage, a hallmark of acute toxoplasmosis, to silence genes necessary for merozoites, a developmental stage critical for subsequent sexual commitment and transmission to the next host, including humans. Their conditional and simultaneous depletion leads to a marked change in the transcriptional program, promoting a full transition from tachyzoites to merozoites. These in vitro-cultured pre-gametes have unique protein markers and undergo typical asexual endopolygenic division cycles. In tachyzoites, AP2XII-1 and AP2XI-2 bind DNA as heterodimers at merozoite promoters and recruit MORC and HDAC3 (ref. $^{1}$), thereby limiting chromatin accessibility and transcription. Consequently, the commitment to merogony stems from a profound epigenetic rewiring orchestrated by AP2XII-1 and AP2XI-2. Successful production of merozoites in vitro paves the way for future studies on Toxoplasma sexual development without the need for cat infections and holds promise for the development of therapies to prevent parasite transmission

Towards automated crystallographic structure refinement with phenix.refine

phenix.refine is a program within the PHENIX package that supports crystallographic structure refinement against experimental data with a wide range of upper resolution limits using a large repertoire of model parameterizations. This paper presents an overview of the major phenix.refine features, with extensive literature references for readers interested in more detailed discussions of the methods

Spinal-cardiac crosstalk

International audienceIn the context of multiple drug intoxication (alprazolam, tramadol and alcohol), a 43-year-old female was admitted to our ICU for hypotension, alteration of consciousness and C4-level tetraplegia. She was found unconscious with her neck in prolonged hyperflexion (90°) for at least 12-h. Oro-tracheal intubation was performed for respiratory failure. A spinal MRI showed cervical myelitis, major para-vertebral and muscular edema facing the lesion (Fig. 1) while echocardiography found an aspect of stress-induced cardiomyopathy with development of a refractory cardiogenic-shock requiring venoarterial-ECMO. She recovered a normal cardiac function and consciousness with persistence of C4-tetraplegia and mechanical ventilation dependency due to central diaphragm paralysis. The cerebrospinal fluid showed a mild hyperproteinorachy without leukocytes, auto anti-body, IgG intrathecal synthesis, or viral genome detection. In addition, cerebral MRI was normal. Despite corticosteroid bolus, her neurological condition did not improve and she passed away from ventilator-associated pneumonia one month later

Q5 Le Quaternaire, Limites et spécificités - Première partie

Colloque international organisé par le CNF-INQUA et l'AFEQ Muséum national d'Histoire naturelle (Paris, 1-3 février 2006

In vitro production of cat-restricted Toxoplasma pre-sexual stages by epigenetic reprogramming

Sexual reproduction of Toxoplasma gondii, which is restricted to the small intestine of felids, is sparsely documented, due to ethical concerns surrounding the use of cats as model organisms. Chromatin modifiers dictate the developmental fate of the parasite during its multistage life cycle, but their targeting to stage-specific cistromes is poorly described1. In this study, we found that transcription factors AP2XII-1 and AP2XI-2, expressed in tachyzoite stage that causes acute toxoplasmosis, can silence genes necessary for merozoites, a developmental stage critical for sexual commitment and transmission to the next host, including humans. Their conditional and simultaneous depletion leads to a drastic change in the transcriptional program, promoting a complete transition from tachyzoites to merozoites. Pre-gametes produced in vitro under these conditions are characterized by specific protein markers and undergo typical asexual endopolygenic division cycles. In tachyzoites, AP2XII-1 and AP2XI-2 bind DNA as heterodimers at merozoite promoters and recruit the epigenitors MORC and HDAC31, which in turn restrict the accessibility of chromatin to the transcriptional machinery. Thus, the commitment to merogony stems from a profound epigenetic rewiring orchestrated by AP2XII-1 and AP2XI-2. This effective in vitro culture of merozoites paves the way to explore Toxoplasma sexual reproduction without the need to infect kittens and has potential for the development of therapeutics to block parasite transmission

Characterization of a novel, stage-specific, invariant surface protein in Trypanosoma brucei containing an internal, serine-rich, repetitive motif.

A new surface membrane protein, invariant surface glycoprotein termed ISG100, was identified in Trypanosoma brucei, using catalyzed surface, radioiodination of intact cells. This integral membrane glycoprotein was purified by a combination of detergent extraction, lectin-affinity, and ion-exchange chromatography followed by preparative SDS-polyacrylamide gel electrophoresis. The protein was expressed only in bloodstream forms of the parasite, was heavily N-glycosylated, and was present in different clonal variants of the same serodeme as well as in different serodemes. The gene for this protein was isolated by screening a cDNA expression library with antibodies against the purified protein followed by screening of a genomic library. The nucleotide sequence of the gene (4050 base pairs) predicted a highly reiterative polypeptide containing three distinct domains, a unique N-terminal domain of about 10 kDa containing three potential N-glycosylation sites, which was followed by a large internal domain consisting entirely of 72 consecutive copies of a serine-rich, 17-amino acid motif (approximately 113 kDa) and terminated with an apparent transmembrane spanning region of about 3.3 kDa. The internal repeat region of this gene (3672 base pairs) represents the largest reiterative coding sequence to be fully characterized in any species of trypanosome. There was no significant homology with other known proteins, and overall the predicted protein was extremely hydrophobic. Unlike the genes for other surface proteins, the gene encoding ISG100 was present as a single copy. Although present in the flagellar pocket, ISG100 was predominantly associated with components of the pathways for endo/exocytosis, such as intracellular vesicles located in the proximity of the pocket as well a large, electron-lucent perinuclear digestive vacuole.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Delivery decision in pregnant women rescued by ECMO for severe ARDS: a retrospective multicenter cohort study

International audienceAbstract Background Although rarely addressed in the literature, a key question in the care of critically pregnant women with severe acute respiratory distress syndrome (ARDS), especially at the time of extracorporeal membrane oxygenation (ECMO) decision, is whether delivery might substantially improve the mother’s and child’s conditions. This multicenter, retrospective cohort aims to report maternal and fetal short- and long-term outcomes of pregnant women with ECMO-rescued severe ARDS according to the timing of the delivery decision taken before or after ECMO cannulation. Methods We included critically ill women with ongoing pregnancy or within 15 days after a maternal/child-rescue-aimed delivery supported by ECMO for a severe ARDS between October 2009 and August 2021 in four ECMO centers. Clinical characteristics, critical care management, complications, and hospital discharge status for both mothers and children were collected. Long-term outcomes and premature birth complications were assessed. Results Among 563 women on venovenous ECMO during the study period, 11 were cannulated during an ongoing pregnancy at a median (range) of 25 (21–29) gestational weeks, and 13 after an emergency delivery performed at 32 (17–39) weeks of gestation. Pre-ECMO PaO2/FiO2 ratio was 57 (26–98) and did not differ between the two groups. Patients on ECMO after delivery reported more major bleeding (46 vs. 18%, p = 0.05) than those with ongoing pregnancy. Overall, the maternal hospital survival was 88%, which was not different between the two groups. Four (36%) of pregnant women had a spontaneous expulsion on ECMO, and fetal survival was higher when ECMO was set after delivery (92% vs. 55%, p = 0.03). Among newborns alive, no severe preterm morbidity or long-term sequelae were reported. Conclusion Continuation of the pregnancy on ECMO support carries a significant risk of fetal death while improving prematurity-related morbidity in alive newborns with no difference in maternal outcomes. Decisions regarding timing, place, and mode of delivery should be taken and regularly (re)assess by a multidisciplinary team in experienced ECMO centers. </jats:sec