During larval development, germ cells divide from the two present at hatching to about a thousand in adults by a variable pattern of divisions to generate. These germline divisions are controlled by a combination of Notch signaling and RNA regulation. The fbf genes,
fbf-1 and
fbf-2, encode members of the Puf family of RNA binding proteins (Wickens et al 2002).
fbf-1 fbf-2 double mutants proliferate normally during early larval stages, but all germ cells enter into meiosis during L4 and differentiate as sperm (Crittenden et al 2002). We have found that two other genes,
fog-1 and
fog-3, can be critical for germline divisions during L1 and L2. FOG-1 is a CPEB homologue required for the sperm fate (Barton and Kimble 1991; Jin et al, 2001), and FOG-3 is a Tob family protein also required the sperm fate (Ellis and Kimble, 1995; Chen et al 2000). The germline proliferates normally in both
fog-1 and
fog-3 single mutants, but they make no sperm and instead make oocytes continuously. However, in an
fbf-1 fbf-2 double mutant background, a reduction of either
fog-1 or
fog-3 by RNAi results in a germline with a reduced number of germ cells compared to the
fbf-1 fbf-2 double mutant. Most commonly there appear to be only 4-16 cells; these cells appear to be oocytes; no cell death has been observed. We are currently building the
fog-1;
fbf-1 fbf-2 triple mutant to characterize these defects in more depth. Progress will be reported at the meeting. Wickens et al (2002) Trends in Genetics 18(3), 150-157; Crittenden et al (2002) Nature 417, 660-663; Barton and Kimble (1991) Genetics 125, 29-39; Jin et al (2001) Developmental Biology 229, 537-553; Ellis and Kimble (1995) Genetics 139, 561-577; Chen et al (2000) Developmental Biology 217, 77-90