On November 18th 2025, Fatima Taiki has defended her PhD thesis entitled “Optimization of vitreous cryo-sectioning for cryo electron tomography imaging of eukaryotic chromosomes in situ”, realized under the supervision of Amélie Leforestier and Mikhail Eltsov (IGBMC, Illkirch).
This work focuses on optimization of vitreous cryo-sectioning for cryo electron tomography (cryo-ET) to study chromatin structure directly in its native cellular and organismal environment. The goal was to overcome the main technical challenges that have long limited the use of cryo-sectioning for cryo-ET, particularly poor section adhesion, instability during imaging, and low throughput. To address these issues, she developed a series of methodological solutions, including a two-step electrostatic charging procedure to enhance section attachment to electron microscopy grids, and identified optimal support films that combine mechanical stability with adhesivity. These advances made it possible to routinely collect large numbers of high-quality tomograms from tissue samples.
She applied these methodological developments to image interphase chromatin in situ in Drosophila melanogaster embryos. By combining optimized vitrification and cryo-sectioning workflows with Volta Phase Plate imaging and deep-learning–based computational denoising, she obtained in situ cryo-ET datasets that enabled direct identification of nucleosomes and linker DNA within native chromatin. Leading to quantification of linker geometry, observation of nucleosome conformational variability, and revealed the presence nucleosomal particles that accommodate from less than one and up to three DNA gyres.
Overall, Fatima Taiki’s work shows that, when optimized, cryo-sectioning can be a robust alternative to cryo-FIB milling for structural studies of tissues and multicellular organisms. It also provides a promising basis for future investigations of chromatin organization and its relationship to gene regulation at the molecular level.
Congratulations Fatima !
