Plakoglobin is a mechanoresponsive regulator of naïve pluripotency

Biomechanical cues are instrumental in guiding embryonic development and cell differentiation. Understanding how these physical stimuli translate into transcriptional programs could provide insight into mechanisms underlying mammalian pre-implantation development. Here, we explore this by exerting microenvironmental control over mouse embryonic stem cells (ESCs). Microfluidic encapsulation of ESCs in agarose microgels stabilized the naïve pluripotency network and specifically induced expression of Plakoglobin (Jup), a vertebrate homologue of ß-catenin. Indeed, overexpression of Plakoglobin was sufficient to fully re-establish the naïve pluripotency gene regulatory network under metastable pluripotency conditions, as confirmed by single-cell transcriptome profiling. Finally, we found that in the epiblast, Plakoglobin was exclusively expressed at the blastocyst stage in human and mouse embryos – further strengthening the link between Plakoglobin and naïve pluripotency in vivo. Our work reveals Plakoglobin as a mechanosensitive regulator of naïve pluripotency and provides a paradigm to interrogate the effects of volumetric confinement on cell-fate transitions. Overall design: Mouse embryonic stem cells were encapsulated in soft agarose microgels, cultured and RNA-seq profiles were obtained and compared with cells cultured on tissue culture plastic. The study revealed the up-regulation of plakoglobin (Jup) in microgels. Single-cell RNA sequencing using inDrop of cells overexpressing plakoglobin demonstrates a re-establishment of pluripotency under metastable culture.