We found that loss of either
eor-1 or
eor-2function results in identical differentiation defects in RMED/V neurons (Huang and Jin, 2019a; Huang and Jin, 2019b). EOR-1 and EOR-2 are thought to positively regulate RAS and WNT signaling pathways in vulval cell induction and in P12 cell fate specification (Howard and Sundaram, 2002). Genetic double mutant analysis suggests that
eor-1 and
eor-2function redundantly with the Mediator complex proteins
sur-2and lin-25 (Howard and Sundaram, 2002). We wished to test whether RAS and WNT signaling pathways are involved in RMED/V differentiation. We examined Punc-25GFP expression in several RAS and WNT mutants (Huang et al., 2004). In the canonical RAS signaling pathway, the EGF-like growth factor LIN-3 binds its receptor LET-23, which then activates LET-60/ras and the MAP kinase cascade that includes LIN-45/raf (MAPKKK),MEK-2/MEK (MAPKK) and MPK-1/ERK (MAPK). We examined strong loss-of-function or putative null mutations in these genes. We detected mild defects in RMED/V cells in
lin-3(
n1059) and
lin-45(
n2018cs) mutant animals. Twenty-two percentage of
lin-3(
n1059)mutants lost Punc-25GFP expression in RMED, and 13% lost the expression in RMEV (N=45). Fifteen percentage and 21% of
lin-45(
n2018cs) animals at non-permissive temperature did not express Punc-25GFP in RMED and RMEV, respectively (N=86) (Table 1). However, similar phenotypes were not found in several other alleles of
lin-3and lin-45 (Table 1). In addition, mutations in LET-23/EGFR, SEM-5, an adaptor protein, MEK-2/MAPKK and MPK-1/MAPK, had little or no effects on Punc-25GFP expression in RMED/V (Table 1). The
let-60(
n1046) dominant mutation also did not affect RMEs.
lin-25has been shown to act in parallel to
eor-1and eor-2in vulva induction, and also did not show any effects on RME. We observed similar results in mutants for the canonical WNT signaling genes including
egl-20/WNT,
pry-1/Axinand
bar-1/b-catenin (Table 1). Therefore, these data suggest that the function of EOR-1 and EOR-2 in RMED/V neurons is likely independent of canonical RAS and WNT pathways.