Protocol to Determine Mitotic Index by FACS

Fluorescence Activated Cell Sorting (FACS) is a sensitive method to count mitotic cells. Cells are stained with an antibody that recognizes an antigen present only in mitotic cells, combined with propidium iodide (PI) to stain DNA. Two-dimensional FACS scanning allows the differential quantitation of G2 and mitotic cells. Several antibodies to different mitotic markers have been used in the community, including antibodies to MPM-2 antigens present in mitotic cells. MPM-2 recognizes a phosphorylated epitope (LTPLK or YWFSPL) 6, 7 in a distinct class of phosphoproteins including MAP2, HSP70, cdc25, and DNA topoisomerase IIα, most of which are phosphorylated at the onset of mitosis. The commercial availability and specificity of antibodies to histone H3 phosphorylated at threonine 11, which is present only in mitotic cells, has also been widely used to detect mitosis cells.

Mitotic cells

FACS

MPM-2 antigens