Genetic analysis of
dpy-29 has provided evidence that this locus defines a single, cryptic, sdc-like gene with separately mutable sex determination and dosage compensation functions. However, unlike sdc- 1 and
sdc-2, mutations in
dpy-29 exhibit two distinct classes of phenotypes, Tra or Dpy. The canonical
dpy-29(Tra) allele,
y52, causes transformation of XX animals into pseudomales, but shows no evidence of dosage compensation defects. In contrast, XX animals homozygous for a null allele of
dpy-29 exhibit only the phenotypes associated with the disruption of dosage compensation (i.e. XX-specific lethality and dumpiness), but no masculinization. The masculinization caused by Tra alleles of
dpy-29 can be suppressed in two ways. First, mutations that upset dosage compensation in XX animals (either in the dosage compensation function of
dpy-29, or in the dosage compensation genes
dpy-21,
dpy-27, or
dpy-28) suppress the transformation by
dpy-29(Tra) alleles. Second, Tra alleles can be suppressed by mutations in
her-1, suggesting that
dpy-29(Tra) mutations disrupt the negative regulation of
her-1 in XX animals ( DeLong, Plenefisch and Meyer, WBG 11(2): 118). Since
her-1 is known to be regulated at the mRNA level (C. Trent and W. Wood, personal communication), we investigated whether
y52 causes increased
her-1 mRNA levels in XX animals as predicted by the genetics. Furthermore, since upsets in dosage compensation suppress this masculinization, we were interested in determining if this suppression was also evident in the level of
her-1 mRNA In order to address these questions, we have measured steady state
her-1 mRNA levels in various strains using Northern analysis. All mRNA was isolated from eggs in order to equalize for stage-specific differences in
her-1 expression. Furthermore, all
her-1 mRNA levels were normalized to
act-1 mRNA levels to control for amounts of mRNA loaded.
dpy-29(Tra) mutations cause overexpression of
her-1 transcripts. mRNA isolated from the weak
dpy-29(Tra) mutation
y137, which causes 26% of the XX animals to be masculinized, showed 20-fold elevation of
her-1 mRNA levels compared to N2. The strong
dpy-29(Tra) mutation,
y52, showed an approximately 50-fold elevation in
her-1 levels. In order to obtain eggs from
y52, the masculinization phenotype was suppressed by
her-1(
e1520), which blocks
her-1 gene function but does not effect
her-1 mRNA levels in XX or XO animals (C. Trent, personal communication). Disruptions in dosage compensation suppress overexpression of
her-1 in
dpy-29(
y52) XX animals. Masculinization caused by
dpy-29(Tra) mutations is suppressed by upsets in dosage compensation. Therefore, we were interested in determining if the suppression of
dpy-29(Tra) by dosage compensation defects acted through
her-1 or if it affected the sex determination pathway at a step downstream of
her-1. We have found that disruptions in dosage compensation do in fact cause a substantial decrease in
her-1 mRNA levels in
dpy-29(Tra) animals, indicating the suppression is mediated either upstream of, or directly on,
her-1. Both
dpy-27(
y57); 2) and
dpy-28(
y1ts);
dpy-29(
y62) have significantly lower
her-1 mRNA levels as compared to the levels in
dpy-29(
y52) in the absence of a dosage compensation defect. This is particularly significant in the case of suppression by
dpy-28(
y1ts) because the animals were grown at the permissive temperature where the dosage compensation defect is slight. However, in both cases some residual expression of
her-1 mRNA above N2 levels remained despite the complete phenotypic suppression of
dpy-29(
y52).In addition, we have examined the effects of loss-of-function mutations in both the dosage compensation
(y180) and sex determination (
y62) functions of
dpy-29 on
her-1 mRNA The balanced strain
dpy-29(
y52y180) /unc-61
(e228) 11) showed a reduced
her-1 mRNA level compared to the
dpy-29(
y62)/unc-61
(e228) 11) strain, but has an equivalent level to that seen in N2. We conclude that the sex determination function of
dpy-29 is required for the proper negative regulation of
her-1 mRNA levels in XX animals. However, defects in dosage compensation suppress the masculinization of
dpy-29(Tra) XX animals by restoring
her-1 mRNA levels to nearly normal. [See Figure 1]