hlh-27 was expressed in four of the EMS granddaughters (MSaa, MSap, MSpa, Mspp). Approximately 25 min after ABp first contacts a ligand-expressing cell at the four-cell stage, all
ref-1 family members were expressed in the ABp granddaughters. No expression was detected in ABa descendants or descendants of other early blastomeres such as EMS or P3. The second Notch interaction begins at the 12-cell stage, when two of the four ABa descendants contact a ligand-expressing cell. The
ref-1 family was expressed about 25 min later in the daughters of the two Notch-activated ABa descendants, but not in other ABa descendants; these same embryos continued to show expression in the ABp descendants activated by the first interaction.