Worm Breeder's Gazette 10(3): 12
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.
Animals homozygous for mutations in the fog-1 gene, both XX and XO, exhibit a feminized germ line. Germ cells that would normally have developed into sperm instead become oocytes. Somatic tissues remain unaffected. We are interested in this locus because it may shed light on how global sex determination signals are interpreted in a particular tissue, in this case the germ line. We are currently investigating the null phenotype of fog-1. Although mutations at fog- 1 come up at a frequency similar to that of loss-of-function mutations at other loci (S. Maples, personal communication), they do show a dominant phenotype: fog-1/+ males make a limited number of sperm and then make oocytes. Experiments where a duplication was tested over 0, 1 or 2 wildtype copies of fog-1 show that the fog-1 mutation acts as one would expect a loss-of-function mutation to act. [See Figure 1] If the fog-1 mutations are in fact loss-of-function alleles and their dominance is due to haplo-insufficiency, then a male hemizygous for the locus would be predicted to display the same phenotype as a male of genotype fog-1/+, i.e. make sperm and oocytes. To test this prediction, we generated deletions in the region around fog-1. This was done by selecting for deletions of unc-11 on the basis of its aldicarb resistance (thanks to C. Johnson and J. Rand for advice). Wild-type hermaphrodites were mutagenized with gamma-rays and crossed to unc-11 s. Crosses were transferred to plates containing 1mM aldicarb after about one day and resistant progeny were picked. Four events were recovered from an estimated 6000 chromosomes. One of these four, qDf3, is a deficiency that fails to complement unc-11, of the others, two are viable unc-11 alleles, one is a deficiency that does not cover fog-1). Males and hermaphrodites of genotype fog-1/qDf3 are identical to animals of genotype fog-1/fog-1, i.e. their germ lines produce only oocytes. However, males of genotype qDf3/+ had phenotypically wild-type germ lines. Whereas oocytes are typically seen in fog-1/+ males one day past L4, no oocytes were seen in qDf3 animals as late as 5 days past L4. Since the phenotype of fog-1/qDf3 is Fog, we are currently isolating new alleles of the locus by a non-complementation screen. Alleles isolated in this unbiased way will allow us to establish the null phenotype of the fog-1 locus. [See Figure 2]