Micron resolved in vivo tomographic time-lapse series of early neurulation in Xenopus laevis acquired by X-ray propagation based phase-contrast imaging

Induction, maturization, delamination, collective directional and individual migration as well as the invasion of target tissue by pluripotent Cranial Neural Crest Cells (CNCC) are essential processes anticipating differentiation subsequent to neurulation. They possibly represent useful models for cancer progression. During the collective migration stage local cell-cell interactions seem to be key to directionality. A quantitative in vivo assessment of temporal characteristics for the average rate of cell-cell contact formation within a given CNCC population via transient protrusions, associated changes in cell polarization, and of the chemical and mechanical interrelation between CNCC and adjacent tissue should provide some basic information to understand collective migration. Here we present micron spatially and ten-minute temporally resolved in vivo time-lapse series of 3D quantitatively reconstructed electron density, exhibiting the development of entire Xenopus laevis embryos throughout initial stages 17 to 23 (neurulation). Lengths of time-lapse series range from 20 to 70 min. Because the underlying tomographic stacks were acquired using X-ray propagation based phase contrast subject to quasimonochromatic, hard synchrotron radiation, single and large propagation distances could be employed. Because of the increased signal-to-noise ratio at all frequencies contained within the intensity contrast and a good recovery of higher-frequency information for retrieved phase maps this allowed for the application of a comparably low dose at prescribed contrast and resolution goal. The here presented reconstructions rely on raw data collected at beamlines 32-ID of Advanced Photon Source and ID19 of European Sychrotron Radiation Facility throughout the years 20122015. Background & Summary In Xenopus laevis the Cranial Neural Crest forms populations of highly motile and pluripotent cells – Cranial Neural Crest Cells (CNCC) – , which possibly are induced at early gastrulation along the border between neural plate and epidermis [1,2], see however [3], emigrate shortly before neural tube closure from the anterior neural plate, and migrate ventrally into the