Multiple Xpa In vivo crystallization routes in HEK 293 human cells

Phase changes of macromolecules in living cells gained recently a major interest in cell biology as liquid liquid phase separation or liquid solid phase transition phenomenon being observed in increasing number of biological or pathological processes. Comprehensive characterization of these phases remains challenging and requires new methodological approaches for their complete description across spatial and temporal scales. We propose a combination of imaging methods applied to a model system and report the in vivo crystallization pathways of a macromolecule from its solution to crystalline states at the cell population level down to the meso scale. Combining various live fluorescence based techniques and a high resolution cryo imaging technique within unaltered cryopreserved cells, we could described the unexpectedly wide landscape of the in vivo crystalline states of the fluorescent coral derived protein xpa, gain information of crystal growth dynamics in cellulo, and provide hypothesis of the crystal nucleation requirements of this stochastic process.