ASYMMETRIC CELL DIVISION CONTROLS HEMATOPOIETIC STEM CELL METABOLIC ACTIVATION AND DIFFERENTIATION

Abstract

Hematopoietic stem cells (HSCs) can self-renew while differentiating to replenish the blood system lifelong. Asymmetric cell division (ACD) has been hypothesized as the mechanism balancing HSC self-renewal and differentiation. In this model, asymmetric daughter cell fates are determined by a mechanism linked to mitosis, e.g. the unequal inheritance of cell fate determinants into daughters. However, due to lacking technology, this mechanism could never been shown directly. Thus, it is also possible that HSCs do not divide asymmetrically, and differentiation is determined by post-mitotic mechanisms. Asymmetric inheritance of cell fate determinants has been reported in progenitor divisions of other tissues. However, low frequencies of HSCs and the technical challenges of continuous quantitative analysis of single suspension cells have prevented the study of HSC mitosis. Few studies therefore provide evidence for asymmetric inheritance of proteins during HSC division, and none was able to demonstrate that future daughter cell fates correlate with this asymmetric inheritance. Here, using continuous quantitative single cell imaging with clustering dimensionality reduction approaches of dynamic single cell behavior, we identify molecules and organelles that are asymmetrically inherited with the lysosomal machinery during HSC divisions. Importantly, we demonstrate that this asymmetric inheritance also predicts future metabolic activation, translation and the overall heterogeneity during differentiation of the HSC daughters. We further show that this mechanism is conserved from mouse to man. We provide the first direct quantitative evidence that HSCs utilize ACD, that future daughter cells fates are prospectively determined by asymmetric mitotic molecule inheritance, and provide insights into the underlying molecular mechanisms for improved therapeutic HSC manipulation.