Leukemia inhibitory factor (LIF)/STAT3 signalling is a hallmark of naive pluripotency in rodent pluripotent stem cells (PSCs), whereas fibroblast growth factor (FGF)-2 and activin/nodal signalling is ...required to sustain self-renewal of human PSCs in a condition referred to as the primed state. It is unknown why LIF/STAT3 signalling alone fails to sustain pluripotency in human PSCs. Here we show that the forced expression of the hormone-dependent STAT3-ER (ER, ligand-binding domain of the human oestrogen receptor) in combination with 2i/LIF and tamoxifen allows human PSCs to escape from the primed state and enter a state characterized by the activation of STAT3 target genes and long-term self-renewal in FGF2- and feeder-free conditions. These cells acquire growth properties, a gene expression profile and an epigenetic landscape closer to those described in mouse naive PSCs. Together, these results show that temporarily increasing STAT3 activity is sufficient to reprogramme human PSCs to naive-like pluripotent cells.
Krüppel-like factors (Klf) 4 and 5 are two closely related members of the Klf family, known to play key roles in cell cycle regulation, somatic cell reprogramming and pluripotency. Here we focus on ...the functional divergence between Klf4 and Klf5 in the inhibition of mouse embryonic stem (ES) cell differentiation. Using microarrays and chromatin immunoprecipitation coupled to ultra-high-throughput DNA sequencing, we show that Klf4 negatively regulates the expression of endodermal markers in the undifferentiated ES cells, including transcription factors involved in the commitment of pluripotent stem cells to endoderm differentiation. Knockdown of Klf4 enhances differentiation towards visceral and definitive endoderm. In contrast, Klf5 negatively regulates the expression of mesodermal markers, some of which control commitment to the mesoderm lineage, and knockdown of Klf5 specifically enhances differentiation towards mesoderm. We conclude that Klf4 and Klf5 differentially inhibit mesoderm and endoderm differentiation in murine ES cells.
Rabbit induced pluripotent stem cells (rbiPSCs) possess the characteristic features of primed pluripotency as defined in rodents and primates. In the present study, we reprogrammed rbiPSCs using ...human Krüppel-like factors (KLFs) 2 and 4 and cultured them in a medium supplemented with fetal calf serum and leukemia inhibitory factor. These cells (designated rbEKA) were propagated by enzymatic dissociation for at least 30 passages, during which they maintained a normal karyotype. This new culturing protocol resulted in transcriptional and epigenetic reconfiguration, as substantiated by the expression of transcription factors and the presence of histone modifications associated with naïve pluripotency. Furthermore, microarray analysis of rbiPSCs, rbEKA cells, rabbit ICM cells, and rabbit epiblast showed that the global gene expression profile of the reprogrammed rbiPSCs was more similar to that of rabbit ICM and epiblast cells. Injection of rbEKA cells into 8-cell stage rabbit embryos resulted in extensive colonization of ICM in 9% early-blastocysts (E3.5), epiblast in 10% mid-blastocysts (E4.5), and embryonic disk in 1.4% pre-gastrulae (E6). Thus, these results indicate that KLF2 and KLF4 triggered the conversion of rbiPSCs into epiblast-like, embryo colonization-competent PSCs. Our results highlight some of the requirements to achieve bona fide chimeric competency.
•Engineered iPS cells show a transcriptome more akin to rabbit epiblast.•Engineered iPS cells show transcriptome and epigenome more akin to naïve pluripotency.•Engineered iPS cells colonize rabbit ICM.•Engineered iPS cells participate in epiblast expansion.•A molecular tool box for studying pluripotent stem cells in rabbits
Conventional rabbit embryonic stem cell (ESC) lines are derived from the inner cell mass (ICM) of pre-implantation embryos using methods and culture conditions that are established for primate ESCs. ...In this study, we explored the capacity of the rabbit ICM to give rise to ESC lines using conditions similar to those utilized to generate naive ESCs in mice. On single-cell dissociation and culture in fibroblast growth factor 2 (FGF2)-free, serum-supplemented medium, rabbit ICMs gave rise to ESC lines lacking the DNA-damage checkpoint in the G1 phase like mouse ESCs, and with a pluripotency gene expression profile closer to the rabbit ICM/epiblast profiles. These cell lines can be converted to FGF2-dependent ESCs after culture in conventional conditions. They can also colonize the rabbit pre-implantation embryo. These results indicate that rabbit epiblast cells can be coaxed toward different types of pluripotent stem cells and reveal the dynamics of pluripotent states in rabbit ESCs.
•Generation of rabbit ESCs lacking DNA-damage checkpoint in G1•Transcriptional profiles of rabbit ESC lines vary depending on culture conditions•Rabbit ESCs can switch between states, revealing plasticity•Some rabbit ESCs can colonize the rabbit pre-implantation embryo
Savatier, Afanassieff, and colleagues report the generation of rabbit ESC lines with gene expression profiles and cell-cycle characteristics closer to those of the rabbit epiblast and mouse ESCs than what was previously reported for rbESC conventional cells. These ESC lines can switch between different states, revealing the dynamics of pluripotency states. Some of these ESC lines acquired the capacity to colonize the rabbit embryo.
Depuis plusieurs années, de nouvelles formes d’agriculture urbaine se font jour en France, questionnant la recherche et ses liens à l’action. La recherche se mobilise donc pour connaître et évaluer ...ce phénomène, qui interroge les relations entre urbains et leurs connexions aux espaces à la nature et à l’alimentation : fonctionnements technico-économiques de ces agricultures, spécificités des sols urbains, enjeux fonciers et services écosystémiques rendus. Le livre s’interroge sur les formes sociales des agricultures urbaines et sur leurs places dans les systèmes alimentaires des territoires. Constatant la forte appétence des collectivités, des habitants et autres acteurs de la ville pour ces agricultures, l’ouvrage présente des produits de recherches conduites avec des acteurs publics et associatifs, professionnels et opérateurs économiques : plateforme collaborative, jeu sérieux, logiciels d’aide à la décision, applis, observatoire participatif, méthodes et guides pour l’action... Un état des lieux des formations existantes en agriculture urbaine est proposé, soulignant les défis à relever et les conditions nécessaires pour développer les agricultures urbaines.. Cet ouvrage est destiné aux étudiants, aux enseignants et aux chercheurs, ainsi qu’aux acteurs publics et privés de l’aménagement urbain, du développement agricole et des politiques alimentaires.
Depuis plusieurs annees, de nouvelles formes d'agriculture urbaine se font jour en France, questionnant la recherche et ses liens a l'action. La recherche se mobilise donc pour connaitre et evaluer ...ce phenomene, qui interroge les relations entre urbains et leurs connexions aux espaces a la nature et a l'alimentation : fonctionnements technico-economiques de ces agricultures, specificites des sols urbains, enjeux fonciers et services ecosystemiques rendus. Le livre s'interroge sur les formes sociales des agricultures urbaines et sur leurs places dans les systemes alimentaires des territoires. Constatant la forte appetence des collectivites, des habitants et autres acteurs de la ville pour ces agricultures, l'ouvrage presente des produits de recherches conduites avec des acteurs publics et associatifs, professionnels et operateurs economiques : plateforme collaborative, jeu serieux, logiciels d'aide a la decision, applis, observatoire participatif, methodes et guides pour l'action... Un etat des lieux des formations existantes en agriculture urbaine est propose, soulignant les defis a relever et les conditions necessaires pour developper les agricultures urbaines.. Cet ouvrage est destine aux etudiants, aux enseignants et aux chercheurs, ainsi qu'aux acteurs publics et prives de l'amenagement urbain, du developpement agricole et des politiques alimentaires.
Transcranial ultrasound stimulation (TUS) is a non-invasive brain stimulation technique; when skull aberrations are compensated for, this technique allows, with millimetric accuracy, circumvention of ...the invasive surgical procedure associated with deep brain stimulation (DBS) and the limited spatial specificity of transcranial magnetic stimulation.
/hypothesis: We hypothesize that MR-guided low-power TUS can induce a sustained decrease of tremor power in patients suffering from medically refractive essential tremor.
The dominant hand only was targeted, and two anatomical sites were sonicated in this exploratory study: the ventral intermediate nucleus of the thalamus (VIM) and the dentato-rubro-thalamic tract (DRT). Patients (N = 9) were equipped with MR-compatible accelerometers attached to their hands to monitor their tremor in real-time during TUS.
VIM neurostimulations followed by a low-duty cycle (5 %) DRT stimulation induced a substantial decrease in the tremor power in four patients, with a minimum of 89.9 % reduction when compared with the baseline power a few minutes after the DRT stimulation. The only patient stimulated in the VIM only and with a low duty cycle (5 %) also experienced a sustained reduction of the tremor (up to 93.4 %). Four patients (N = 4) did not respond. The temperature at target was 37.2 ± 1.4 °C compared to 36.8 ± 1.4 °C for a 3 cm away control point.
MR-guided low power TUS can induce a substantial and sustained decrease of tremor power. Follow-up studies need to be conducted to reproduce the effect and better to understand the variability of the response amongst patients. MR thermometry during neurostimulations showed no significant thermal rise, supporting a mechanical effect.
•Transcranial Ultrasound Stimulation induced more than 89 % reduction of essential tremor in 5 patients.•A sustained effect (more than 23min) was observed in 3 patients.•Stimulation was performed in the VIM and the DRT.•No significant thermal rise was measured by MR Thermometry during stimulation.
The global emergence of Zika virus (ZIKV) revealed the unprecedented ability for a mosquito-borne virus to cause congenital birth defects. A puzzling aspect of ZIKV emergence is that all human ...outbreaks and birth defects to date have been exclusively associated with the Asian ZIKV lineage, despite a growing body of laboratory evidence pointing towards higher transmissibility and pathogenicity of the African ZIKV lineage. Whether this apparent paradox reflects the use of relatively old African ZIKV strains in most laboratory studies is unclear. Here, we experimentally compare seven low-passage ZIKV strains representing the recently circulating viral genetic diversity. We find that recent African ZIKV strains display higher transmissibility in mosquitoes and higher lethality in both adult and fetal mice than their Asian counterparts. We emphasize the high epidemic potential of African ZIKV strains and suggest that they could more easily go unnoticed by public health surveillance systems than Asian strains due to their propensity to cause fetal loss rather than birth defects.
Focusing ultrasound through the skull requires accurate correction of skull induced aberrations. Acoustic lenses provide an inexpensive and effective measure for correcting these distortions. This ...study explores a phase unwrapping technique for designing multi-frequency acoustic lenses coupled with geometrically focused transducers. Here, we demonstrate numerically and theoretically that in a homogeneous medium and for a single target steered from the natural focus of the transducer, a wrapped lens can only work at its design frequency, while a phase unwrapped lens is broadband. This concept is further explored in experiments where three human skulls are inserted between a transducer and its natural focus. Unwrapped lenses are used to correct for the skull aberrating effect at multiple frequencies and are compared to their wrapped counterparts. Such experiments demonstrate that the unwrapped lenses are the only ones capable of correcting for skull aberrations in a broad range of frequencies. At the design frequency of the lenses, the unwrapped lenses perform quantitatively better than their wrapped counterparts since the average intensity behind three skulls was found to be 49% lower with a phase wrapped lens compared to a phase unwrapped lens, even if both allow to qualitatively refocus the wave at the desired targets. In addition, such results confirm the necessity to correct for skull aberrations, since the field may be highly distorted in the absence of aberration correction.
Magnetic resonance guided transcranial focused ultrasound holds great promises for treating neurological disorders. This technique relies on skull aberration correction which requires computed ...tomography (CT) scans of the skull of the patients. Recently, ultra-short time-echo (UTE) magnetic resonance (MR) sequences have unleashed the MRI potential to reveal internal bone structures. In this study, we measure the efficacy of transcranial aberration correction using UTE images. Approach. We compare the efficacy of transcranial aberration correction using UTE scans to CT based correction on four skulls and two targets using a clinical device (Exablate Neuro, Insightec, Israel). We also evaluate the performance of a custom ray tracing algorithm using both UTE and CT estimates of acoustic properties and compare these against the performance of the manufacturer's proprietary aberration correction software. Main results. UTE estimated skull maps in Hounsfield units (HU) had a mean absolute error of 242 ± 20 HU (n=4). The UTE skull maps were sufficiently accurate to improve pressure at the target (no correction: 0.44 ± 0.10, UTE correction: 0.79 ± 0.05, manufacturer CT: 0.80 ± 0.05), pressure confinement ratios (no correction: 0.45 ± 0.10, UTE correction: 0.80 ± 0.05, manufacturer CT: 0.81 ± 0.05), and targeting error (no correction: 1.06 ± 0.42 mm, UTE correction 0.30 ± 0.23 mm, manufacturer CT: 0.32 ± 0.22) (n=8 for all values). When using CT, our ray tracing algorithm performed slightly better than UTE based correction with pressure at the target (UTE: 0.79 ± 0.05, CT: 0.84 ± 0.04), pressure confinement ratios (UTE: 0.80 ± 0.05, CT: 0.84 ± 0.04), and targeting error (UTE: 0.30 ± 0.23 mm, CT: 0.17 ± 0.15). Significance. These 3D transcranial measurements suggest that UTE sequences could replace CT scans in the case of MR guided focused ultrasound with minimal reduction in performance which will avoid ionizing radiation exposure to the patients and reduce procedure time and cost.
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