Figure 4. Overexpression of hSMN in wild-type organisms interferes with the normal puparial axial ratio in a similar manner to Gem3^ΔN, and induces the formation of spherical aggregates.

(A) Top, Puparia of flies with ubiquitous overexpression of hSMN (da-GAL4>hSMN), pan-muscular overexpression of hSMN (how-GAL4>hSMN) or Gem3^ΔN (how-GAL4>Gem3 ^ΔN), and their respective GAL4 driver controls (da-GAL4/+ or how-GAL4/+). Bottom, Chart displaying the axial ratios for puparia of the indicated genotype. Ubiquitous or pan-muscular overexpression of hSMN results in significantly larger puparial axial ratios. Although ubiquitous overexpression of Gem3^ΔN results in lethality prior to puparium formation, its pan-muscular overexpression results in puparia with a significantly large axial ratio. The mean is marked by a horizontal line running through the data points and error bars are ± S.E.M. (***p<0.001). (B) Larval muscles (delineated by dashed white outline) showing the formation of hSMN-positive spherical aggregates of variable size in the cytoplasm and nucleus of flies with a ubiquitous ectopic overexpression of hSMN. Within the nucleus, these foci localise to the nucleolus, which is the region with low Hoechst reactivity (insert, scale bar = 5 µm). Aggregates were not visible in control (da-GAL4/+) tissues subjected to the same immunostaining reaction, thereby excluding the possibility of non-specific reactivity.