Fig. 7.

Model of cut action in NB death. (A) As neural stem cells age, they show an overall increase in repressive chromatin, marked by H3K27me3. Expression of cut inhibits this increase, at least in part through enhancement of cohesin expression. A more open configuration in the grim/rpr region allows the NB enhancer, activated by additional cell type-specific spatial and temporal factors, to turn on the transcription of grim and rpr leading to properly programmed cell death. (B) When cut expression is suppressed, SA and possibly other cohesin subunits decline, allowing a premature increase in H3K27me3 in NBs. At the grim/rpr locus, this blocks expression in response to upstream apoptosis regulatory factors.