Different isoforms of Maxwell´s Demon, a conserved cell membrane protein, mediate lose/win decisions during cell competition. Drosophila melanogaster

Cell competition promotes the elimination of weaker cells from a growing population. Here we investigate how cells of Drosophila wing imaginal discs distinguish “winners” from “losers” during cell competition. Using genomic and functional assays we have identified Maxwell`s Demon (Mwd), a cell membrane protein conserved in multicellular animals. Our results suggest that the membrane protein Mwd is a dedicated component of the cell competition response that is required and sufficient to label cells as “winners” or “losers”. In Drosophila, the mwd locus produces three isoforms, mwdubi, mwdLose-A and mwdLose-B. Basal levels of mwdubi are constantly produced. During competition the mwdLose isoforms are upregulated in prospective loser cells. Cell-cell comparison of relative mwdLose and mwdubi levels ultimately determine which cell undergoes apoptosis. This “extracellular code” may constitute an ancient mechanism to terminate competitive conflicts among cells. Overall design: Two samples have been analysed: tub>dmyc>Gal4 transgene cells (competitor) and tub>cd2>Gal4 control cells (non competitor) at different time points (0, 12, 24 and 48 hours). Each experiment was replicated 6 times, three of them by dye swap.