Forkhead transcription factors are a large family of sequence-specific DNA binding proteins.These proteins have been identified in many species across diverse phyla, and have been implicated as regulators of a number of important developmental processes. The completion of the C. elegans genome sequencing project has allowed the identification of all the forkhead genes within the worm, and permits the simultaneous study of this family of proteins. There are 15 forkhead genes in C. elegans, of which five have been previously characterised, i.e.
daf-16,
lin-31,
pes-1,
pha-4, and
unc-130. We have concentrated our studies on the other ten, that is : B0286.5, C25A1.2, C29F7.4, C29F7.5, C39H7.3, F26A1.2, F26B1.7, F40H3.4, K03C7.2, and T14G12.4. We have characterised these genes by generating lacZ and/or GFP expression patterns and RNA interference. (The results of our studies of T14G12.4 are discussed in the abstract of S. Aslam et al.) Unsurprisingly, the expression studies reveal that forkhead genes are expressed at various stages of development, and in a variety of tissues, including pharynx, neurons, and the developing gonad. Consistent with reverse genetic analyses of other gene families, only two of the forkhead genes (F26B1.7 and B0286.5) gave an obvious RNAi phenotype. F26B1.7 is expressed in the anterior of the embryo from an early stage (approximately 200 cells) until after elongation, and has a highly pleiotropic and variably penetrant RNAi phenotype. This phenotype includes larval lethality, aberrant oocyte and somatic gonad development, apparent absence of a uterus, and adult morbidity. B0286.5 is expressed in the developing somatic gonad (including the spermathecae), and consistent with this many worms show a sterile RNAi phenotype. In occasional animals, one arm of the gonad will produce fertilised embryos but few, or none, are laid and the uterus becomes bloated with eggs.