Figure 4

Polyploid DNA content by FACS and lack of contact inhibition in NEK1 -/- cells. RTEs cultured from NEK1 -/- mice and from wild type littermates were harvested at different passages during exponential phase growth, stained with propidium iodide, and quantified with FACS for DNA content. A. Wild type cells show sharp 2n and 4n peaks in early and late passage cells. B. NEK1 -/- cells show 2n and 4n peaks at early passages. As cells proliferate in culture, 2n population cells disappear and cells with DNA content between 2n and 4n increase in later generations. NEK1 -/- cells surviving at higher passages have >6n DNA content; few 2n or 4n cells are seen. (C, D.) Growth properties of wild type and NEK1 -/- cells. Cells at passage 3 or 9 were cultured until they reached 100% confluence, and then cultured for additional of 2 weeks, until no more proliferation was observed in wild type cells. NEK1 -/- cells continued to pile, beyond monolayers. C. Representative morphology of the cells immediately before harvest. D. Saturation density of cells was quantified as number of cells per cm². Each histogram represents mean ± standard error from 2 different cell lines in duplicate plates.