Probable transcriptional repressor required for the deposition of dimethylated 'Lys-9' of histone H3 (H3K9me2) on asynapsed chromosome pairs (both autosomes and sex chromosomes) during meiosis, but this does not seem to solely affect the transcriptional status (PubMed:21909284). Plays a role in ray fusion and patterning in the male tail, and this may be through activity of the histone deacetylase complex (HDAC) (PubMed:17506990). Component of the SIN3S complex, which contains at least sin-3, hda-1, athp-1 and mrg-1 (PubMed:31602465). Interacts with ztf-11; the interaction is weak (PubMed:31386623). Interacts with cfp-1 (PubMed:31602465). Expressed in all ray structural cells including ray 6, 7, 8 and 9 of the male tail. Also expressed in the inner labial neurons, socket cells, the cephalic neurons in the head and the ventral nerve cord. Expressed from the L1 stage of larval development to adulthood. Uncoordinated movement, protruding vulva and ray fusion defects in the male tail (PubMed:17506990). RNAi-mediated knockdown results in sterility (PubMed:16710447). RNAi-mediated knockdown in a him-8 mutant background results in no deposition of dimethylated 'Lys-9' of histone H3 (H3K9me2) on asynapsed chromosome pairs (PubMed:21909284).