Worm Breeder's Gazette 15(1): 77 (October 1, 1997)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Department of Biology, University of Michigan, Ann Arbor MI 48109
fog-1 is a regulatory gene that is required for specification of spermatogenesis in the germ line of C. elegans. In fog-1 mutants, germ cells that would normally develop into sperm become oocytes instead. Over 60 fog-1 mutations are known. To better understand how these mutations affect the fog-1 gene, we have used a sensitive assay to study the effects that different alleles have on sperm production. Animals homozygous for a fog-1 mutation could not be used to study spermatogenesis because these animals do not make any sperm. Therefore, we used animals with a fog-1 mutation in trans to fog-1(q253ts) to determine the relative strengths of 16 fog-1 alleles. q253ts is a weak, temperature sensitive allele that causes XX animals to become self-sterile at 25 degrees C. Below 25, however, fog-1(q253ts) animals are self-fertile. Therefore, controlling the temperature at which experiments are run allows us to control the relative activity of the fog-1(q253ts) gene product. These experiments were done at the permissive temperature of 15 degrees C. In this assay, the percentage of females (which produce no sperm) among fog-1(?)/fog-1(q253) animals at 15 degrees C served as a measure of fog-1 allele strength. The null phenotype was defined using qDf4, a deficiency that completely removes the fog-1 gene. Our results show that the alleles can be divided into three groups: null (10-20% females), weak (0% females), and dominant negative (>30% females). We conclude: (1) The deficiency qDf3 behaves like a weak fog-1 allele; (2) likely null alleles are q325 and q241; (3) the dominant negative alleles are likely to encode a product that interferes with the specification of spermatogenesis, which suggests that FOG-1 might bind to itself or another protein. Although fog-1 is required for spermatogenesis in both males and hermaphrodites, it is possible that it interacts with different proteins in the two sexes. To determine the effect of dominant negative alleles on spermatogenesis in males, we are conducting sperm counts in fog-1(?)/fog-1(q253ts) worms. L4 males of the desired genotype were picked to separate plates to ensure that no sperm were lost by mating. When the males reached adulthood and had switched to producing oocytes, DAPI staining was used to count sperm under fluorescent microscopy. Initial data suggests that dominant negative alleles of fog-1 have the greatest effect on spermatogenesis in males, just as in hermaphrodites. fog-1(?)/fog-1(q253) XX at 15 C fog-1(?)/fog-1(q253) XO at 15 C allele %fem #herm %fem allele average # of sperm q253ts 0 105 0.00 q187 27 +/- 9 oz15ts 0 22 0.00 q493 50 +/- 32 qDf3 0 88 0.00 e2121 86 +/- 22 e2121 13 146 8.18 q325 115 +/- 9 qDf4 5 45 10.00 q325 13 93 12.26 q241 14 84 14.29 q242 20 78 20.41 q491 44 90 32.84 q218 28 40 41.18 q507 29 21 58.00 q180 67 38 63.81 q492 21 7 75.00 q254 133 12 91.72 q187 198 3 98.51 q493 102 1 99.03