Spatio-temporal analyses of OCT4 expression and fate transitions in human embryonic stem cells

OCT4 is one of the transcription factors required to maintain a pluripotent state in human embryonic stem cells (hESCs). The quantification -both temporal and spatial- of the molecular interactions controlling pluripotency and differentiation are relevant for the development of successful mathematical and computational models incorporating a systemic view in which the various building elements and their interplay are considered. We analyse the changes of OCT4-mCherry intensity expression in a hESC colony in the presence and absence of the BMP4 morphogenetic protein. We show that OCT4 expression is dynamic. We obtain the stationary probability distributions that govern the hESCs transitions amongst the different cell states in the presence/absence of BMP4 and establish the times at which the hESCs, that lead to differentiated and pluripotent cells, cluster in the colony. Furthermore, by quantifying the similarities between the OCT4 expression amongst neighbouring hESCs, we show that hESCs express, on average, similar values in their local neighbourhood within the first two days of the experiment and before BMP4 treatment. Our framework allows us to quantify the relevant properties of proliferating hESC colonies. We believe our procedure is widely applicable to other transcription factors and cell populations.