Until recently the inimitable potency of pluripotent cells has been known to be regulated by a combination of genetics, epigenetics and external factors. We were the first to discover that pluripotent cells develop and mature into distinct cell types also based on the functions of their inner scaffolding, known as the microtubule cytoskeleton, which was until then widely regarded as disorganised and its contribution to cell fate specification was largely ignored.
Inside a cell, organelles and proteins are usually not randomly distributed but are assigned to regions where they are needed. The cell utilises the microtubule cytoskeleton as the road map to localise organelles and to trigger the relay of signals intra- and intercellularly. By performing innovative live imaging of preimplantation mouse embryos and human induced pluripotent stem cells, we discovered an unprecedented form of non-centrosomal microtubule organisation required for the formation and maintenance of pluripotency. Dependent on the microtubule anchor and nucleator Calmodulin-Spectrin associated protein 3 (CAMSAP3), this form of non-centrosomal microtubule organisation orchestrates the asymmetric distribution of rRNAs, mRNAs, tRNAs and organelles involved in translation inside pluripotent cells which results in an unequal inheritance of information, and differential cell fate decisions of daughter cells. By applying innovative light-switchable microtubule destabilisers, we demonstrated the inability of pluripotent cells to specify their fates due to failing in establishing intracellular asymmetries.
Our discoveries complement the genetic knowledge of pluripotency during mammalian embryogenesis by advancing our understanding on the dynamic regulation of the intracellular organisation, orchestrated by the microtubule cytoskeleton, is critical for this feature. By addressing the knowledge gap in the cell biological properties of pluripotent cells, we can harness this knowledge to develop novel therapeutics for regenerative medicine and fertility.