In the C. elegans germ line, GLP-1/Notch signaling regulates the germline stem cell proliferation versus meiotic entry decision. Two redundant pathways,
gld-1/nos-3 and
gld-2/gld-3, function downstream of GLP-1/Notch signaling to either inhibit proliferation and/or promote meiotic development. Enhancer screens have been performed to identify additional genes that function in regulating the proliferation versus differentiation decision. One screen was designed to find mutations that enhance the tumourous phenotype of a weak
glp-1 gain-of-function allele (gf). The genes corresponding to these mutants are likely to be either general negative regulars of GLP-1/Notch signaling, or positive regulators of meiotic entry (functioning downstream of Notch signaling). One of the genes identified in this screen was given the name
teg-2 (tumourous enhancer of
glp-1 weak gf). Using a variety of mapping and cloning methods, we have found
teg-2 to be allelic to
puf-8 (pumilio and fbf).
puf-8 encodes an RNA-binding protein that belongs to the family of Puf proteins (homologous to Drosophila Pumilio). Previous studies have suggested roles for
puf-8 in the C. elegans germ line [1,2,4] and during vulva development [3]. We have identified an additional function for
puf-8 in the C. elegans germ line; to inhibit proliferation of germline stem cells. We have observed that loss of
puf-8 enhances the overproliferative phenotype of three
glp-1(gf) alleles (
ar202,
oz264 and
oz112oz120) and is also able to suppress the Glp phenotype of a partial loss of function
glp-1 mutant (
bn18).
puf-8 is not synthetically tumourous with the known genes functioning downstream of GLP-1/Notch signaling,
gld-1,
nos-3,
gld-2 and
gld-3, suggesting that
puf-8 does not function in this portion of the pathway to promote meiotic development.
puf-8 mutants have previously been observed to have excess proximal proliferation due to dedifferentiation of spermatocytes [1]. To determine if the overproliferation we observe in
puf-8;
glp-1(gf) mutants is due to a disruption of the proliferation/differentiation decision or dedifferentiation, we made
puf-8;
glp-1(gf);
spe-6 and
puf-8;
glp-1(gf);
fem-3 mutants. Both
spe-6 and
fem-3 were previously shown to suppress the dedifferentiation tumour in
puf-8 single mutants [1]; however, in a
glp-1(gf) background, we did not see suppression of the tumourous phenotype. This suggests that the
puf-8;
glp-1(gf) tumour is due to a disruption in the proliferation/differentiation decision.(1. Subramaniam, K. and Seydoux, G. (2003). 13, 134-9) (2. Bachorik, J. L. and Kimble, J. (2005). 102, 10893-7) (3. Walser, C. B., et al. (2006). 133, 3461-71) (4. Ariz, M., et al. (2009). 326, 295-304).