Figure 5.

Like L44, Q45 enhances R388 mutant effects in trans. (A) Expression of the Q45 mutation alone in spastin null flies (H^Q45,Ø) rescues eclosion to the same level as H^WT (P > 0.2). In contrast, ∼40% fewer H^Q45,H^R388 compound heterozygotes eclose compared with H^WT,H^R388 single mutants, although for the numbers tested this effect did not achieve a P-value of <0.05 (P = 0.06). Q45 may therefore be a weaker intragenic modifier of catalytic mutations compared with L44. (B, C) Bouton number in H^Q45,H^R388 compound heterozygotes is increased, similar to nulls (P > 0.07), and significantly greater than in single heterozygotes (H^WT,H^R388 or H^Q45,Ø; P < 0.03). Expression of the H^Q45 mutation alone in the null background restores bouton number and microtubule distribution to near wild-type levels. Arrows in (C) denote examples of terminal boutons.