Year 2

The past year has seen excellent progress across all of our Specific Aims. Specifically:

i) We have made the first, to our knowledge, quantitative measurements of intercellular mechanical force transmission between human embryonic stem cells (hESCs). This powerful technology has the capacity to transform our understanding of the molecular and physical underpinnings of tissue and organ morphogenesis.

ii) We identified probable proteins that control stem cell proliferation and pluripotency maintenance. We used a high-throughput proteomics strategy to identify proteins that are likely to regulate the localization and activity of transcription factors that regulate cell proliferation specifically in hESCs. This experiment revealed both previously known and novel players in this complex signaling network. Excitingly, newly identified proteins suggest the presence of uninvestigated mechanically activated signaling pathways in hESCs.

iii) We created tunable stiffness substrates for hESC culture with completely defined molecular composition. This tool is required to recreate the physical environment of the early embryo, and is expected to be critical discovering the molecular pathways that underlie mechanically directed hESC differentiation.

iv) We found that the expression levels and conformation of a specific protein that regulates cell-cell adhesion influence hESC colony morphology and adhesiveness. Separate, non-CIRM funded research in the Dunn lab showed that this same protein is likely a master mechanosensor at cell-cell junctions (Buckley et al. Science 2014). Together, these data hint at an underlying molecular mechanism that may direct the formation and shape of living tissues.