Figure 2.

Hdac1 mutations enhance the homeotic effects of Psc mutations in embryos. Wild-type embryos (A and E) or embryos homozygous for Hdac1³⁰³ (B and F), Psc^e24 (C and G), or Psc^e24 Hdac1³⁰³ (D and H) were stained with either ABD-B (A–D) or UBX antibody (E–H). Ventral nerve cords of these embryos were dissected out and displayed with the anterior to the top. In wild-type embryos, ABD-B expression normally is restricted to PS10–14, with a gradual increase toward the posterior end (A), whereas strong and highly modulated UBX expression is restricted to PS5–12, with weak expression in small clusters of cells in PS4 and PS13 (E). These patterns were not affected in Hdac1³⁰³ (B and F) or Df(3R)10H homozygotes (data not shown). ABD-B expression extended to more anterior PS at low levels in Psc^e24 homozygotes (C) and at much higher levels in Psc^e24 Hdac1³⁰³ double homozygotes (D). Similarly, ectopic UBX expression was somewhat sporadic and at lower levels in Psc^e24 homozygous embryos (arrowheads in G), but was more extensive and much stronger in Psc^e24 Hdac1³⁰³ double homozygotes (arrowheads in H). In addition, UBX expression became stronger in PS5, but reduced in abdominal parasegments in both Psc^e24 homozygotes (G) and Psc^e24 Hdac1³⁰³ double homozygotes (H). The effects appeared to be much stronger in double mutants than in single mutants. The designation of genotypes was based on the frequency of the novel patterns produced from heterozygous parents, i.e., 20 to ≈25% and ≈3.3% (11 of 336 embryos) for single and double mutants, respectively. Although Hdac1 mutants did not show aberrant homeotic gene expressions, their ventral nerve cords were slightly distorted in the abdominal region.