Caspase activation is required for terminal erythroid differentiation

The cysteine proteases known as caspases play a central role in most apopto tic pathways. Here, we show that caspase inhibitors arrest the maturation o f human erythroid progenitors at early stages of differentiation, before nu cleus and chromatin condensation. Effector caspases such as caspase-3 are t ransiently activated through the mitochondrial pathway during erythroblast differentiation and cleave proteins involved in nucleus integrity (lamin B) and chromatin condensation (acinus) without inducing cell death and cleava ge of GATA-1. These observations indicate a new function for caspases as ke y proteases in the process of erythroid differentiation.