fox-1 was previously identified as a candidate numerator element based on its overexpression phenotype. FOX-1 is an RRM-type RNA-binding protein, which can bind RNAs in vitro. Western analysis detects FOX-1 throughout development.
fox-1::lacZ comes on ubiquitously early during embryogenesis. Postembryonically,
fox-1::lacZ is expressed sex specifically in a subset of cells in the head and tail. We describe a Tc1-derived deletion allele [
fox-1(Delta)] that removes the RRM domain.
fox-1(Delta) confers no phenotype in XXs, but can rescue XO-specific lethality and feminization caused by duplications of the left end of the X.
fox-1(Delta) synergizes with putative numerators, resulting in abnormal XX development. Genetic analysis indicated that
fox-1(Delta) leads to a slight increase in
xol-1 activity, while
fox-1(gf) leads to partial loss of
xol-1 activity, and
xol-1 is epistatic to
fox-1. RNase protection experiments revealed increased levels of the 2.2-kb
xol-1 message in
fox-1(Delta) animals, and reduced levels in
fox-1(gf) animals. Additionally,
fox-1(Delta) impairs male mating efficiency, which, we propose, represents another function of
fox-1, independent of
xol-1 and its role in sex determination.