לוח שנה משולב

During postimplantation development of the mouse embryo, descendants of the inner cell mass cells in the early epiblast transit from the naïve pluripotent state to the primed pluripotent state. Concurrent with the transition of the pluripotency states is the specification of cell lineages and formation of germ layers in the embryos that serves as the blueprint for embryogenesis. Fate mapping and lineage analysis studies have revealed that cells in different regions of the germ layers acquire location-specific cell fates during gastrulation. The regionalization of cell fates heralding the formation of the basic body plan is conserved in vertebrate embryos at a common phylotypic stage of development. Knowledge of the molecular regulation that underpins the lineage specification and tissue patterning is instrumental for understanding embryonic programming and stem cell-based translational study. However, a genome-wide molecular annotation of lineage segregation and tissue architecture of post-implantation embryo has yet to be undertaken. Here, we reported a spatially resolved transcriptome of cell populations at defined positions in the germ layers over the period of pre- to late gastrulation development. This spatio-temporal transcriptome provides high resolution digitized in situ gene expression profiles and defines the molecular attribute of the genealogy of lineages and continuum of pluripotency states in time and space. The transcriptome further identifies the networks of molecular determinants that drive lineage specification and tissue patterning in the early postimplantation mouse embryo.

TBA

The NMR spectra of molecular species in solution mixtures can be separated with diffusion-ordered NMR spectroscopy (DOSY), a ‘virtual chromatography’ approach based on the measurement of translational diffusion coefficients. Classic DOSY experiments, however, require several minutes are not applicable to many important time-evolving mixtures.
Taking advantage of the concept of spatial encoding, we show here that DOSY data can be collected in a single scan of less than one second for several types of out-of-equilibrium mixtures. SPEN provides an acceleration of DOSY experiments by several orders of magnitude. SPEN DOSY pulse sequences are developed, that compensate for convection effects and are suitable for measurements in low-viscosity organic solvents, a requirement to monitor organic chemical reactions. We also show how to collect multiple consecutive scans from short-lived, non-renewable signals produced by dissolution dynamic nuclear polarisation (D-DNP), which is a versatile and powerful hyperpolarisation method. These methodological developments are supported by advanced numerical simulations, based on a Fokker-Plank formalism to describe simultaneously the spin and spatial dynamics. An exemple of hyperpolarised sample is given with a model mixture of small molecules, while the ability to monitor a reacting mixture is illustrated with a diamination reaction in dichloromethane.
The proposed UF DOSY methodology may contribute towards a real-time diffusion NMR analysis of mixtures, to help in the identification of a sample’s components and in the analysis of molecular interactions.