3.5. Subpopulation Analyses of Suspension Cultures
In suspension cultures, there were no clear subpopulations of cells
based on PCA. However, there remained the possibility of hidden
subpopulations of cells. We generated histograms of gene expression and
found a gene, enolase, that had a multipeak distribution. We divided the
individual D4 cells into groups with high enolase expression
(giI625221705IrefIXM_003512016.2I; 2000–4200 RPM) and low enolase
expression (0–2000 RPM; Figure 5a) and used PCA to analyze these
individual D4 cells. The PC1 of the individual D4 cells were plotted
against those for PC2. Individual D4 cells with high and low enolase
expression formed distinct clusters (Figure 5b), which represents the
hidden subpopulations of CHO cells in suspension cultures. This
phenomenon is contrary to expectations. Hidden cellular subpopulations
such as those found in this study hint at the future discovery of
intrinsic factors giving rise to cell-to-cell variability in cell
populations.