I have frequently seen endoreduplication (that is, a doubling of the DNA content) in cultured cell lines, particularly if they have been drug treated. Cells sometimes move from G2 to G1 without going through mitosis and dividing. When measuring a DNA histogram you should always check for single cells with a DNA content greater than G2. If these cells are present you should also look for a G2 population associated with the endoreduplicated population. I would have expected that the endoreduplicated cells would divide more slowly than the normal cells but this is not the case. The endoreduplicated cells can take over the culture and therefore must either be dividing faster or losing less through cell death. Regards, Michael G. Ormerod, 34 Wray Park Road, Reigate, RH2 0DE, UK +44 (0)1737 241726 mobile: 07802 293242 ----- Original Message ----- From: Ron Hill To: Cytometry Mailing List Sent: Tuesday, December 11, 2001 11:01 PM Subject: DNA Measurement Hi All, One of our users has observed an apparent doubling in the amount of DNA (based on PI staining) in the 2N population of NIH3T3 cells after selection in drug to establish cell lines that stably express a gene of interest. The cells were engineered by retrovirus. The doubling is compared to the parental cells. The selected cells have a 4N population with 4 times the DNA of parental 2N cells. Has anyone ever seen this. Is it likely to be some artifact of staining? Thanks in advance. Ronald J. Hill, Ph.D. Sr. Group Leader, Research Sugen, Inc. 230 East Grand Ave. South San Francisco, CA 94080 ron-hill@sugen.com tel: 650-837-3797 fax: 650-837-3313
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