High throughput measurement of single HeLa cell volume growth and cell cycle progression using FXm

The way proliferating animal cells coordinate the growth of their mass,
volume, and other relevant size parameters is a long-standing question in
biology. Studies focusing on cell mass have identified patterns of mass
growth as a function of time and cell cycle phase, but little is known
about volume growth. To address this question, we improved our
fluorescence exclusion method of volume measurement (FXm) and obtained
1696 single cell volume growth trajectories of asynchronous HeLa cells
expressing hgeminin-GFP. The data were obtained over four independent
replicates. For each cell, depending on the phase of the cell cycle it was
observed, the following information is indicated: time of birth (onset of
cytokinesis), time of G1/S transition (onset of the expression of
hgeminin-GFP), time of entry into mitosis (onset of mitotic cell
rounding). All the FXm movies and single cell volume trajectories were
visually assessed to check and correct any mistake in the automated
segmentation and lineage tracking that would give false volume
fluctuations measurements. We thus present a dataset of well curated,
high-throughput measurement of single cell volume available for the
investigation of volume growth in animal cells. We find that, during most
of the cell cycle, volume growth is close to exponential and proceeds at a
higher rate in S-G2 than in G1. Comparing the data with a mathematical
model, we establish that the cell-to-cell variability in volume growth
arises from constant-amplitude fluctuations in volume steps, rather than
fluctuations of the underlying specific growth rate. We hypothesize that
such ‘additive noise’ could emerge from the processes that regulate volume
adaptation to biophysical cues, such as tension or osmotic pressure.
Future work combining our single cell volume measurements with the
analysis of single cell mass growth curves will likely provide interesting
perspectives.