Transition state dynamics during a stochastic fate choice

Abstract

The generation of multiple fates from a uniform cell population via selforganisation is a recurring feature in development and regeneration. However, for most self-organising systems, we have little understanding of the processes that allow cells to become different. One of the clearest examples of developmental self-organisation is shown by Dictyostelium, with cells segregating into two major fates, stalk and spore, within multicellular aggregates. To characterise the gene expression decisions that underlie this cell fate bifurcation, we carried out single cell transcriptomics on Dictyostelium aggregates. Our data show the transition of progenitors into prespore and prestalk cells occurs via distinct developmental intermediates. Few cells were captured switching between states, with minimal overlap in fate marker expression between cell types, suggesting states are discrete and transitions rapid. Surprisingly, fate-specific transcript dynamics were a small proportion of overall gene expression changes, with transcript divergence coinciding precisely with large-scale remodelling of the transcriptome shared by prestalk and prespore cells. These observations suggest the stepwise separation of cell identity is temporally coupled to global expression transitions common to both fates.

Cell and molecular transitions during efficient dedifferentiation

“…This implies, as suggested earlier, that most transcriptional changes occur early during dedifferentiation. Notably, the timescale of convergence is similar to that measured for the cell fate separation process during forward developmental progression (Antolovic et al, 2019), implying no strong resistance to cell state change that is specific to dedifferentiation. The efficiency and apparent robustness may be related aspects of the dedifferentiation response.…”

“…Using PC1 as a proxy for developmental time, prespore markers rapidly switch off, whilst the prestalk expression persists in cells with negative PC1 values. These observations are reminiscent of the behaviour of the different cell types during forward development, in which the prestalk cells appear less responsive (Antolovic et al, 2019). The differing behaviours of prestalk and prespore cells during dedifferentiation do not interfere with the convergence of cell states ( Figure 6H).…”

“…To test this possibility, we imaged cell motility and division in a reporter cell line for the stalk fate. The cryS gene is strongly expressed in the prestalk lineage (Antolovic et al, 2019) and we used a CryS-mNeonGreen knock-in reporter to follow the behaviour of the prestalk population during dedifferentiation. The cell line also expressed H2B-mCherry, which facilitates cell tracking.…”

“…This gave 42 prespore markers and 48 prestalk markers. Sets of genes being up-or down-regulated during mound stage of development are taken from (Antolovic et al, 2019).…”

High throughput imaging identifies a spatially localized response of primary fetal pulmonary artery endothelial cells to insulin-like growth factor 1 treatment

“…1 However, in non-clonal primary cells, single-cell heterogeneity could be due to multiple epi-genetic populations, variability due to a stochastic response to fast environmental response changes, or other forms of variability that are just beginning to be explored. [13][14][15] This additional heterogeneity necessitates a careful experimental approach that integrates traditional ensemble readouts with high-throughput single-cell measurements of molecular signaling (Figure 1).…”