Developing a cyclin blueprint as a tool for mapping the cell cycle in GS-NS0

•Proposes an experimental approach to formulate segregated validated cell cycle model.•Identifies and quantifies major cell cycle landmarks in the industrial GS-NS0 cell line.•Quantifies cyclins E1 and B1 expression profiles and transition thresholds.•Identifies cyclin D1's unrelated S phase entrance.

The cell cycle is at the center of growth, productivity, and death of mammalian cell cultures. There exists a need to identify and quantify major landmarks in the cell cycle of industrially relevant mammalian cell lines and its association with productivity; central for designing productivity optimization strategies. Herein, we studied the expression of three cyclins, under both perturbed and unperturbed growth, by flow cytometry in batch cultures of GS-NS0. The perturbed systems involved two different DNA synthesis inhibitors, thymidine and dimethyl sulfoxide (DMSO). This approach enables the establishment of characteristic cyclin profiles, timings, and thresholds. In particular, two G1 class cyclins (D1 and E1), and one G2 cyclin (B1) were investigated. Cyclin B1 showed a clear cell cycle phase-specific expression increasing during G2 phase where it was approximately 40% higher when compared to G1 phase. Similarly, cyclin E1 showed a clear pattern being expressed approximately 10% higher in G1 compared to G2 phase and decreased through S phase. Cyclin D1 expression was fairly invariable throughout the cell cycle phases. The observed patterns provide a blueprint of the cell line's cell cycle, which can be used for the development of biologically accurate and experimentally validated distributed cell cycle models.