Precise mapping of one classic and three novel mutants in .

Mutation of the gene or pharmacological agents targeting it are commonly used to assess homeostatic synaptic function at the larval neuromuscular junction (NMJ). The commonly used mutation, , is a null allele created by a large and imprecise excision of a P-element which affects and multiple upstream genes. Here we mapped the exact bounds of the allele, refined a multiplex PCR strategy for positive identification of in homozygous or heterozygous backgrounds, and sequenced and characterized three new CRISPR-generated mutants. We found the three new alleles are apparent nulls that lack GluRIIA immunofluorescence signal at the 3 instar larval NMJ and are predicted to cause premature truncations at the genetic level. Further, these new mutants have similar electrophysiological outcomes as , including reduced miniature excitatory postsynaptic potential (mEPSP) amplitude and frequency compared to controls, and they express robust homeostatic compensation as evidenced by normal excitatory postsynaptic potential (EPSP) amplitude and elevated quantal content. These findings and new tools extend the capacity of the NMJ for assessment of synaptic function.