Multi-scale imaging and analysis identify pan-embryo cell dynamics of germlayer formation in zebrafish.

The coordination of cell movements across spatio-temporal scales ensures precise positioning of organs during vertebrate gastrulation. Mechanisms governing such morphogenetic movements have been studied only within a local region, a single germlayer or in whole embryos without cell identity. Scale-bridging imaging and automated analysis of cell dynamics are needed for a deeper understanding of tissue formation during gastrulation. Here, we report pan-embryo analyses of formation and dynamics of all three germlayers simultaneously within a developing zebrafish embryo. We show that a distinct distribution of cells in each germlayer is established during early gastrulation via cell movement characteristics that are predominantly determined by their position in the embryo. The differences in initial germlayer distributions are subsequently amplified by a global movement, which organizes the organ precursors along the embryonic body axis, giving rise to the blueprint of organ formation. The tools and data are available as a resource for the community.

Morphogenesis of extra-embryonic tissues directs the remodelling of the mouse embryo at implantation.

Mammalian embryos change shape dramatically upon implantation. The cellular and molecular mechanism underlying this transition are largely unknown. Here, we show that this transition is directed by cross talk between the embryonic epiblast and the first extra-embryonic tissue, the trophectoderm. Specifically, we show via visualisation of a Cdx2-GFP reporter line and pharmacologically mediated loss and gain of function experiments that the epiblast provides FGF signal that results in differential fate acquisition in the multipotent trophectoderm leading to the formation of a tissue boundary within this tissue. The trophectoderm boundary becomes essential for expansion of the tissue into a multi-layered epithelium. Folding of this multi-layered trophectoderm induces spreading of the second extra-embryonic tissue, the primitive endoderm. Together, these events remodel the pre-implantation embryo into its post-implantation cylindrical shape. Our findings uncover how communication between embryonic and extra-embryonic tissues provides positional cues to drive shape changes in mammalian development during implantation.

Prenatal pseudocysts of the germinal matrix in preterm infants.

Sonographic characteristics of germinal-matrix (PGM) pseudocysts of prenatal origin detected on cranial ultrasound in preterm newborns were correlated with their outcomes. PGM cysts were classified as typical or atypical, according to their location. Typical PGM cysts were present at the head of the caudate nucleus or slightly medially, adjacent to the foramen of Monro. Cysts were defined as atypical when they were located subependymally elsewhere. Only one infant of 16 with a typical PGM cyst presented with psychomotor retardation. His cerebral scan also showed subependymal calcifications due to cytomegalovirus infection. Three babies had cysts in the frontal periventricular zones (atypical PGM cyst). They had negative cranial MRI (12-15 months of age) and normal neurological follow-up (24 months). In conclusion, isolated prenatal PGM cysts in preterm infants correlate with a normal outcome.