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Nuclear architecture

Context.  The nucleus is arguably the organelle where the greatest number and variety of cellular functions are carried out: DNA replication, DNA repair, transcription, gene regulation, chromatin remodelling, RNA processing, RNA export, protein import, etc. It has emerged in recent years that most of these functions are carried out in distinct nuclear compartments. Examples of such compartments include the well-known nucleolus, the jack-of-all-trade PML bodies, the round Cajal bodies and the dynamic nuclear speckles [1]. How these compartments are formed and maintained and how they interact with each other to coordinate nuclear functions is an area of intense research. The early C. elegans embryos offers an excellent model to study the formation of nuclear bodies. Not only can the process of nuclear body re-formation be studied after fertilization and each successive mitosis, but differentiation along distinct cell lineages, already apparent at the 2-cell stage in the anterior somatic cell and the posterior germline precursor [2], allows the comparison of nuclear architecture in functionally-distinct cells.

Goal. To analyze the structure and dynamics of the nucleolus, the interchromatin compartment and the transcription factories in early embryonic nuclei of C. elegans.

Methodology. The structure of nuclear compartments is determined using super-resolution 3D structured illumination microscopy. This new technique allows more precise measurements of nuclear body size and number to be made. Fine structural changes can also be observed. Super-resolution analysis of fixed material is done in collaboration with the laboratory of Thomas Cremer in Munich. In addition, worm lines expressing fluorescent reporters (e.g. Nopp140-mCherry) are currently being generated to image the formation and dynamics of nuclear bodies in the living embryo.