Size Control

Supercells Outcompete Their Neighbors

Science's STKE  13 Apr 2004:
Vol. 2004, Issue 228, pp. tw129-TW129
DOI: 10.1126/stke.2282004TW129

Mutations that increase cell size or proliferation rates can alter organ size or organism size, or both. In mosaic organisms or tissues in which only a subset of the cells carry the mutation, the situation is more complex, and sometimes these animals or tissues can be of normal size. Experiments with flies expressing cells carrying mutations in ribosomal-protein genes suggested that these cells did not compete effectively with their wild-type neighbors and were eliminated; this process was termed "cell competition." Two groups investigated the phenomenon of cell competition that occurs in response to altering the expression of Drosophila myc (dmyc) in the precursor cells that form the fly wing. De La Cova et al. showed that wings composed of dmyc-overexpressing cells and wild-type cells were normal in size, and that this apparent normal wing size was the result of increased death of wild-type cells near the dmyc-overexpressing cells. Cell death required the gene head involution defective (hid), which encodes a proapoptotic protein. When dmyc expression was restricted to a strip of cells separating the anterior from the posterior region, the ability of dMyc to promote neighboring cell death appeared to be limited to cells in the anterior region, which showed increased expression of hid. Moreno and Basler reported similar results, with a correlation between dMyc abundance and expansion of cells in clones with increased copies of the dmyc gene at the expense of cells with fewer copies of the gene. Apoptotic cell death in the cells expressing less dMyc was inhibited by activation of the Decapentaplegic (Dpp) pathway (through genetic methods). Thus, competition for a limiting survival factor may contribute to the ability of the dMyc superexpressors to outcompete their neighbors. On this issue, the two groups reported divergent results, with de La Cova et al. showing that Dpp target-gene expression was not changed and Moreno and Basler showing that Dpp target-gene expression was altered in a manner reflective of decreased Dpp signaling in cells adjacent to the dMyc overexpressors.

C. de La Cova, M. Abril, P. Belosta, P. Gallant, L. A. Johnston, Drosophila Myc regulates organ size by inducing cell competition. Cell 117, 107-116 (2004). [Online Journal]

E. Moreno, K. Basler, dMyc transforms cells into super-competitors. Cell 117, 117-129 (2004). [Online Journal]