The pupal lethality of any of the following mutants: Nrd1Q376X, Nrd1R540X, Nrd1W369X or Nrd1K134X can be rescued by combination with Nrd1+t5. It also rescues the age-dependent loss of synaptic transmission in photoreceptor cells in adult flies carrying Nrd1Q376X somatic clones in the retina.