“…While both increase and decrease in dynamic range with age do occur, here we specifically focused on increases in variance and its effect on the loss of lineage fidelity with age. Accordingly, in single-cell studies, aged cells were shown to have increased transcriptional variability and loss of transcriptional coordination compared to younger cells of the same tissue [Kowalczyk et al, 2015, Martinez-Jimenez et al, 2017, Enge et al, 2017, Levy et al, 2020], suggesting that increase in cellular heterogeneity with age underlies the population-level increases in variances between the individuals we observed. As such, the molecular signals of aging cells may not be fully captured as stereotyped directional changes -rather a large fraction of age-associated changes will be reflected as increases in measured variance in the molecular signal across an aged cohort.…”