Probable transcriptional corepressor which modulates activity of the nuclear hormone receptor daf-12 to regulate the dauer diapause. Isoform d interacts with daf-12. Isoform d is widely expressed: detected in the hypodermis, seam cells, intestine, somatic gonad, neurons, vulval precursors, body wall muscle and pharynx. Isoforms b and d are widely expressed from embryogenesis to adulthood. Isoform d is highly expressed in late L1 and L2 larval stages in XXX neuroendocrine cells. Isoform b is expressed more highly in the embryo and the L1 larval stage. Knockout of isoform d results in defective dauer formation. Eighteen percent of temperature sensitive mutants are embryonic lethal. The surviving animals are small (Sma), clear (Clr), uncoordinated, constipated and sterile. They display variable morphological defects in the main body and pharynx.