FrankenCells: how fusing cells together led to an understanding of cell cycle regulation(discussed Oct 12)

image adapted from Rao & Johnson, 1970 (Nature)

In the 1970s and 80s, the cell cycle was HOT. Major outstanding questions remained unanswered: namely how do cells "know" when to duplicate their DNA and divide? The molecular answers to these questions would come later in the decade from mutational experiments, but Rao and Johnson (1970) used a more clever approach: fusing cells in different parts of the cell cycle together and observe the effects on each nucleus's chromatin. If each cell cycle phase (G1, S, G2, M) uses different signaling factors in its cytoplasm, then what happens when those signals mix? Rao and Johnson showed not only that multinucleate cells will synchronize their nuclear division cycles, but that certain phases in the cell cycle can "dominate" over other phases. The authors' ingenuity required no great advances in genetic or optical tools; rather, they used a well-known virus to simply fuse together large populations of cells.

• Mammalian Cell Fusion :  Studies on the Regulation of DNA Synthesis and Mitosis