Apoptosis, G1 Phase Stall, and Premature Differentiation Account for Low Chimeric Competence of Human and Rhesus Monkey Naive Pluripotent Stem Cells

After reprogramming to naive pluripotency, human pluripotent stem cells (PSCs) still exhibit very low ability to make interspecies chimeras. Whether this is because they are inherently devoid of the attributes of chimeric competency or because naive PSCs cannot colonize embryos from distant species remains to be elucidated. Here, we have used different types of mouse, human, and rhesus monkey naive PSCs and analyzed their ability to colonize rabbit and cynomolgus monkey embryos. Mouse embryonic stem cells (ESCs) remained mitotically active and efficiently colonized host embryos. In contrast, primate naive PSCs colonized host embryos with much lower efficiency. Unlike mouse ESCs, they slowed DNA replication after dissociation and, after injection into host embryos, they stalled in the G1 phase and differentiated prematurely, regardless of host species. We conclude that human and non-human primate naive PSCs do not efficiently make chimeras because they are inherently unfit to remain mitotically active during colonization

Patent Foramen Ovale Closure or Anticoagulation vs. Antiplatelets after Stroke

BACKGROUND Trials of patent foramen ovale (PFO) closure to prevent recurrent stroke have been inconclusive. We investigated whether patients with cryptogenic stroke and echocardiographic features representing risk of stroke would benefit from PFO closure or anticoagulation, as compared with antiplatelet therapy. METHODS In a multicenter, randomized, open-label trial, we assigned, in a 1:1:1 ratio, patients 16 to 60 years of age who had had a recent stroke attributed to PFO, with an associated atrial septal aneurysm or large interatrial shunt, to transcatheter PFO closure plus long-term antiplatelet therapy (PFO closure group), antiplatelet therapy alone (antiplatelet-only group), or oral anticoagulation (anticoagulation group) (randomization group 1). Patients with contraindications to anticoagulants or to PFO closure were randomly assigned to the alternative noncontraindicated treatment or to antiplatelet therapy (randomization groups 2 and 3). The primary outcome was occurrence of stroke. The comparison of PFO closure plus antiplatelet therapy with antiplatelet therapy alone was performed with combined data from randomization groups 1 and 2, and the comparison of oral anticoagulation with antiplatelet therapy alone was performed with combined data from randomization groups 1 and 3. RESULTS A total of 663 patients underwent randomization and were followed for a mean (+/- SD) of 5.3 +/- 2.0 years. In the analysis of randomization groups 1 and 2, no stroke occurred among the 238 patients in the PFO closure group, whereas stroke occurred in 14 of the 235 patients in the antiplatelet-only group (hazard ratio, 0.03; 95% confidence interval, 0 to 0.26; P<0.001). Procedural complications from PFO closure occurred in 14 patients (5.9%). The rate of atrial fibrillation was higher in the PFO closure group than in the antiplatelet-only group (4.6% vs. 0.9%, P = 0.02). The number of serious adverse events did not differ significantly between the treatment groups (P = 0.56). In the analysis of randomization groups 1 and 3, stroke occurred in 3 of 187 patients assigned to oral anticoagulants and in 7 of 174 patients assigned to antiplatelet therapy alone. CONCLUSIONS Among patients who had had a recent cryptogenic stroke attributed to PFO with an associated atrial septal aneurysm or large interatrial shunt, the rate of stroke recurrence was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone. PFO closure was associated with an increased risk of atrial fibrillation

Reprogramming of rabbit somatic cells for species conservation

National audienc

An unbiased screening for transcription factors and chromatin remodelers that reset pluripotent stem cells to naïve-like pluripotency

International audienc

The rabbit preimplantation embryo as a paradigm to explore naive pluripotent stem cell derivation in non rodent species

International audienc

Plant–herbivore interactions: Experimental demonstration of genetic variability in plant–plant signalling

International audiencePlant-herbivore interactions mediated by plant-plant signalling have been documented in different species but its within-species variability has hardly been quantified. Here, we tested if herbivore foraging activity on plants was influenced by a prior contact with a damaged plant and if the effect of such plant-plant signalling was variable across 113 natural genotypes of Arabidopsis thaliana. We filmed the activity of the generalist herbivore Cornu aspersum during 1 h on two plants differing only in a prior contact with a damaged plant or not. We recorded each snails' first choice, and measured its first duration on a plant, the proportion of time spent on both plants and leaf consumption. Overall, plant-plant signalling modified the foraging activity of herbivores in A. thaliana. On average, snails spent more time and consumed more of plants that experienced a prior contact with a damaged plant. However, the effects of plant-plant signalling on snail behaviour was variable: depending on genotype identity, plant-plant signalling made undamaged plants more repellant or attractive to snails. Genome-wide associations revealed that genes related to stress coping ability and jasmonate pathway were associated to this variation. Together, our findings highlight the adaptive significance of plant-plant signalling for plant-herbivore interactions

Single-cell qPCR analysis of pluripotency in rabbit embryos

International audienc

Single-cell qPCR analysis of pluripotency in rabbit embryos

International audienceIn the rabbit, many attempts have been made to reprogram pluripotent stem cells (PSC) to the naïve state, but none of the conditions tested could lead the naïve state as defined in the mouse. These previous studies also highlighted differences in the molecular signature of the naïve and primed pluripotency states between rabbit vs. mouse. In order to address these differences and identify new markers of naïve and primed pluripotency in rabbit, it is necessary to characterize in more details the transcriptome of the pluripotent cells in vivo, i.e. in the rabbit embryo. We, therefore, performed a Biomark qPCR single-cell analysis of rabbit embryos around the time of lineage segregation, from the morula stage to the early gastrulating stage. We identified a transcriptomic continuum of pluripotency in vivo specific to the rabbit, although we observed many similarities to the mouse. These results will allow us to judge the state of pluripotency of rabbit PSC we will derive in vitro, as compared to the embryo, and to find new targets to reprogram them towards the naïve state

Deciphering the epigenetic context of pluripotency in rabbit pre-implantation embryos

International audiencePluripotency describes the ability of a stem cell to give rise to all cell types in mature organisms. Two main types of pluripotent stem cells (PSCs) have been described: naïve and primed. In rodents, naïve-state pluripotency characterises mouse embryonic stem cells (mESCs) that have been derived from the pre-implantation epiblast. In primates (human and monkey) and lagomorphs (rabbits), ESCs only exist in the primed state of pluripotency. Primed-state pluripotency characterises the epiblast of developmentally more advanced embryos, with a higher concentration of heterochromatin and an inactivated X chromosome in female cells. The study aimed to decipher the chromatin context of naïve and primed pluripotency in the rabbit embryo, from the compacted morula stage until the onset of the gastrulation in the epiblast. Using immuno-fluorescence, we analysed the distribution of DNA-methylation and hydroxymethylation, Histone 3 lysine 9 and 27 methylation, as well as Histone 2A lysine 119 ubiquitination. In parallel, we analysed the expression of genes encoding the erasers and writers of those epigenetic marks using single-cell Biomark qPCR. From these experiments, we observed a progressive loss of heterochromatin marks in the pluripotent cells of early blastocysts (Inner Cell Mass or ICM), followed by gain of heterochromatin in more advanced stages (in the epiblast). Those variations are associated with the transient downregulation of genes promoting heterochromatin formation in the ICM, while genes promoting euchromatin formation are downregulated in the epiblast. This study helped us to identify the chromatin landscape and its regulators associated to the naïve state of pluripotency in rabbits