The stable maintenance of acquired cell fates is important during development and for maintaining tissue homeostasis. Although histone modification is one of the major strategies used by cells to maintain their fates, the mechanisms by which histone variants maintain cell fates are not well understood. In C. elegans, the acetylated-histone-H4 (AcH4)-binding protein BET-1 acts downstream of the MYST family histone acetyltransferases MYS-1 and MYS-2 to establish and maintain cell fates in multiple cell lineages. Here we show that, in the
bet-1 pathway, the histone H2A variant HTZ-1/H2A.z and MYS-1 are required for the maintenance of cell fates in a redundant manner. BET-1 controlled the subnuclear localization of HTZ-1. HTZ-1 and MYS-1 maintained the fates of the somatic gonadal cells (SGCs) through the repression of a target,
ceh-22/Nkx2.5, which induced the formation of the leader cells of the gonad. H3K27 demethylase, UTX-1, had an antagonistic effect relative to HTZ-1 in the regulation of
ceh-22. Nuclear spot assay revealed that HTZ-1 localized to the
ceh-22 locus in SGCs in an
utx-1-dependent manner. We propose that HTZ-1 and MYS-1 repress
ceh-22 when UTX-1 removes its silencing mark, H3K27 methylation on the
ceh-22 locus, thereby maintaining the fates of SGCs.