Signaling Systems Laboratory, Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA.
A new study in the journal Nature (Spencer et al., 2009) argues that cell-to-cell variation in the decision to undergo apoptosis is not due to genetic, epigenetic, or cell-cycle differences, nor due to random molecular noise, but instead is determined by differences in protein abundances.