Erect wing rescues viability and synaptic growth defects of elav mutants. (a) Rescue of viability of elav mutants by ewg transgenes. An elav-EWG transgene fully rescues viability of a temperature sensitive elav allele (elavts1transheterozygous for the elave5, a null allele); when early functions in neuronal differentiation are provided by rearing flies at the permissive temperature (three days at 18°C and then at 25°C, n = 250-350 animals per genotype). (b-f) Rescue of synaptic growth defects of elav mutants by EWG. Synaptic growth in elavts1/elave5mutants (c,f) is significantly reduced (p ≤ 0.0001) when reared at the restrictive temperature during larval life compared to wild type (b,f) and is rescued by elav-EWG (d,f) and elav-ELAV (e,f). Bouton numbers (type 1b at muscle 13) in (f) are shown as means with standard errors (n = 21-35). Statistical significance of differences from comparisons with wild type is shown on top of bars (***p < 0.0001, n.s. for non significant). Other relevant comparisons are marked by horizontal bars with the statistical significance indicated on the side. The scale bar in (b) is 20 μm.