RNA interference with one of the eight C. elegans linker histones genes triggers desilencing of a repetitive transgene and developmental defects in the hermaphrodite germline. These observations are similar to the phenotype of the C. elegans Polycomb group genes
mes-2,
mes-3,
mes-4, and
mes-6 (9, 18). These Polycomb group proteins contribute to germline specific chromatin modifications. Using a
his-24 deletion mutant and an isoform specific antibody we characterize the role of
his-24 in C. elegans germline development. We describe an unexpected cytoplasmic retention of HIS-24 in peculiar granular structures. This phenomenon is confined to the developing germline of both sexes. It is strictly dependant on the activity of the chromatin modifying genes
mes-2,
mes-3,
mes-4, and
mes-6, as well as on the C. elegans sirtuin
sir-2.1. A temperature shift experiment with a
mes-3(ts) mutant revealed that mes-gene activity is required in a time window ranging from L3 to the early L4 stage before the onset of meiosis. We find that the
his-24(
ok1024) mutant germline is characterized by an increased level of the activating H3K4 methylation mark concomitant with a decrease of the repressive H3K9 methylation. In the germline of
his-24(
ok1024)
mes-3(
bn35) double mutant animals the repressive H3K27 methylation is more reduced than in the respective mes-single -mutant. These observations distinguish
his-24 as an unusual element in the developmental regulation of germline chromatin structure in C. elegans.