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Updated: Aug 8, 2026

Analysis of Cell Cycle Position in Mammalian Cells
Published on: January 21, 2012
Timing the changes of cyclin E cell content in G1 in exponentially growing cells
Daniela Tomasoni1, Monica Lupi, Fadia Bekkal Brikci
1Biophysics Unit, Department of Oncology, Istituto di Ricerche Farmacologiche Mario Negri, Via Eritrea 62, 20157 Milan, Italy.
Abstract:
We present a method for measuring the content of immunocytochemically detected proteins in individual cells progressing through G(1) phase and its application in the analysis of cyclin E levels. The sequence of G(1) events is tracked under unaltered cycling conditions, in a cell line in the phase of balanced growth in vitro, to avoid the pitfalls of synchronization. Cells were pulse-labeled with BrdUrd and analyzed sequentially by multiparameter flow cytometry, focusing on the subpopulation of labeled cells progressively entering G(1). We use the time-from-birth ("age") of individual cells to track their position inside G(1). Using the average content of cyclin E in the whole population of G(1) cells as the internal reference for each sample, we analyzed the time course of the frequency histograms of cyclin E content within BrdUrd-labeled G(1) cells by exploiting the properties of the age distributions of asynchronous populations. This way we could calculate the average cyclin E content of cells in each age cohort. Cyclin E values were low until age 3 h, after which they rose gradually, reaching six times the value of newborn cells at the end of G(1).
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