Proteins of the highly conserved heterochromatin protein 1 (HP1) family have 
been found to function in the dynamic organization of nuclear architecture and 
in gene regulation throughout the eukaryotic kingdom. In addition to being key 
players in heterochromatin-mediated gene silencing, HP1 proteins may also 
contribute to the transcriptional repression of euchromatic genes via the 
recruitment to specific promoters. To investigate the role played by these 
different activities in specific developmental pathways, we identified HP1 
homologues in the genome of Caenorhabditis elegans and used RNA-mediated 
interference to study their function. We show that one of the homologues, HPL-2, 
is required for the formation of a functional germline and for the development 
of the vulva by acting in an Rb-related pathway. We suggest that, by acting as 
repressors of gene expression, HP1 proteins may fulfil specific functions in 
both somatic and germline differentiation processes throughout development.