Clonal analysis of Notch1-expressing cells reveals the existence of unipotent stem cells that retain long-term plasticity in the embryonic mammary gland.

Recent lineage tracing studies have revealed that mammary gland homeostasis relies on unipotent stem cells. However, whether and when lineage restriction occurs during embryonic mammary development, and which signals orchestrate cell fate specification, remain unknown. Using a combination of in vivo clonal analysis with whole mount immunofluorescence and mathematical modelling of clonal dynamics, we found that embryonic multipotent mammary cells become lineage-restricted surprisingly early in development, with evidence for unipotency as early as E12.5 and no statistically discernable bipotency after E15.5. To gain insights into the mechanisms governing the switch from multipotency to unipotency, we used gain-of-function Notch1 mice and demonstrated that Notch activation cell autonomously dictates luminal cell fate specification to both embryonic and basally committed mammary cells. These functional studies have important implications for understanding the signals underlying cell plasticity and serve to clarify how reactivation of embryonic programs in adult cells can lead to cancer.Wellcome Trus

Caractérisation d'un gravimètre quantique différentiel

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Trio GEF mediates RhoA activation downstream of Slit2 and coordinates telencephalic wiring

International audienceTrio, a member of the Dbl family of guanine nucleotide exchange factors, activates Rac1 downstream of netrin 1/DCC signalling in axon outgrowth and guidance. Although it has been proposed that Trio also activates RhoA, the putative upstream factors remain unknown. Here, we show that Slit2 induces Trio-dependent RhoA activation, revealing a crosstalk between Slit and Trio/RhoA signalling. Consistently, we found that RhoA activity is hindered in vivo in T rio mutant mouse embryos. We next studied the development of the ventral telencephalon and thalamocortical axons, which have been previously shown to be controlled by Slit2. Remarkably, this analysis revealed that Trio knockout (KO) mice show phenotypes that bear strong similarities to the ones that have been reported in Slit2 KO mice in both guidepost corridor cells and thalamocortical axon pathfinding in the ventral telencephalon. Taken together, our results show that Trio induces RhoA activation downstream of Slit2, and support a functional role in ensuring the proper positioning of both guidepost cells and a major axonal tract. Our study indicates a novel role for Trio in Slit2 signalling and forebrain wiring, highlighting its role in multiple guidance pathways as well as in biological functions of importance for a factor involved in human brain disorders

Optimization and characterization of a differential quantum gravimeter

International audience<p>Measuring the acceleration of the Earth’s gravity <em>g</em> and the gravity gradient simultaneously and at the same location promises to provide enhanced information about the distribution of underground masses, especially at shallow depths [1]. Quantum sensors relying on Atom Interferometry with laser cooled-atoms [2,3] is a technology of choice to implement such new sensing capability and an industry-grade demonstrator has been recently developed [4] by iXblue.</p><p>This Differential Quantum Gravimeter (DQG) has been operational for more than two years and has demonstrated state-of-the-art sensitivity mainly limited by Quantum Projection Noise down to a noise floor at about 40E/sqrt(tau). We will present as well a 21 day long run with the demonstration of a resolution below 1E for the measurement of the vertical gravity gradient (1E = 10<sup>-9</sup> s<sup>-2</sup> = 0.1 µGal/m) and 0.5 µGal for the measurement of <em>g</em>. Moreover in order to illustrate the potential for mass balance monitoring and gravity survey we will present a proof-of-principle experiment with realistic masses and measurement duration. We will provide insight on an previsional accuracy budget and main biases.</p><p>The compactness of the instrument and the field-tested technology [5] on which it is based, allows to consider the deployment of this new sensor in real environment as a future short-term outcome to investigate both spatial and temporal mass balance in the field. Promising case studies will be discussed, as this type of sensor can sense mass changes that are not detected by gravimeters.</p><p>[1] G. Pajot, O. de Viron, M. M. Diament, M. F. Lequentrec-Lalancette, V. Mikhailov, GEO-PHYSICS <strong>73</strong>, 123 (2008).</p><p>[2] R.Geiger, A.Landragin, S.Merlet, F.P.D.Santos, <em>AVS QuantumScience </em><strong>2</strong>, 024702(2020).</p><p>[3] V. Ménoret et al., "Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter", <em>Nature Scientific Reports</em>, vol. <strong>8</strong>, 12300 (2018)</p><p>[4] A compact differential gravimeter at the quantum projection noise limit,<em> to be published in Physical Review </em>A</p><p>[5] A.-K. Cooke, C. Champollion, N. Le Moigne, <em>Geoscientific Instrumentation, Methods and </em></p><p><em>Data Systems Discussions</em> 2020, <strong>1</strong> (2020).</p&gt

New Developments for Commercial Quantum Gravimeters

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New Developments for Commercial Quantum Gravimeters

International audienc

Pushing the stability of a Differential Quantum Gravimeter below 1Eötvös/1µGal

International audienceOne year after the first signals were obtained with the Differential Quantum Gravimeter (DQG) developed by muquans, we report on the new performances of the instrument. DQG is a unique instrument that combines the ability of simultaneously measuring the local gravity acceleration and its vertical gradient with an industry-grade geophysics-oriented design. Relying on a similar physical principle and same technologies developed for our absolute quantum gravimeters (AQG) [1], a single vertical laser beam simultaneously measures the vertical acceleration experienced by two sets of free-falling laser-cooled atoms from different heights. The vertical acceleration gives a direct access to g, and the difference of both measurements yields to vertical gravity gradient . [2,3]. Our demonstrator has been operational for a year and demonstrated best sensitivities of 53 E/?t, and 360nm/s<SUP>2</SUP>/?t, on the second floor of a university building. Long term stabilities below 1E and 10nm/s<SUP>2</SUP> levels have been obtained on 60 hours long measurements. After presenting the instrument and results, the talk will present the studies led to further improve the capabilities and performances. We will finally present ongoing works on mass detection experiments. Such experiments aim at assessing the accuracy of the instrument as well as its ability to detect and monitor underground density variations, opening new perspectives for applications in geodesy and hydrology.This work has been supported by the DGA, the French Department of Defense, and the ANR GRADUS. [1] V. Ménoret et al., "Gravity measurements below 10?9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)[2] M. J. Snadden et al. "Measurement of the Earth's Gravity Gradient with an Atom Interferometer-Based Gravity Gradiometer" , Phys. Rev. Lett. 81, 971 (1998) [3] R. Caldani et al. "Simultaneous accurate determination of both gravity and its vertical gradient", Phys. Rev. A 99, 033601 (2019

Recent advances in quantum gravity sensors

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New Developments for Commercial Quantum Gravimeters

International audienc

Compact differential gravimeter at the quantum projection-noise limit

International audienc