unc-104¹⁷⁰ ddaC neuron clones within mosaic individuals present mild-to-severe fully penetrant dendrite pruning defects at 16h after puparium formation, as compared to controls; unc-104¹⁷⁰ heterozygotes do not show this defect.

Axon terminals of homozygous R7 photoreceptor cell clones often fail to contact the M6 layer of the medulla.

Homozygous unc-104¹⁷⁰ mutant eyes externally appear normal and their ERGs show robust responses to light. However, the 'on-off transients' of ERG, which require synchronous synaptic transmission from the photoreceptors to second-order neurons, are absent in homozygous mutant eyes.

Homozygous unc-104¹⁷⁰ mutant flies die as unhatched late-stage embryos. The gross morphology of these embryos is comparable to that of a wild-type fly that has completed embryogenesis 20-22hrs after egg-laying. The mutants, however, are paralyzed and lack the coordinated muscle peristalsis required for hatching.

Homozygous unc-104¹⁷⁰ mutant embryos, despite normal axonal outgrowth and targeting, ISNb axon contacts lack extended branches. Filipodia-like structures are sometimes found, but not restricted to muscle boundaries. At 21 hours AEL, the nerve is visible in its target regions, but the contacts have not transformed into mature synapses; the nerves lack the bead-like boutons seen in wild-type embryos. Instead, the endings and their branches are more constricted than those at 14 hours AEL and frequently retain some filipodia-like processes. This phenotype is completely penetrant, observed in every abdominal segment. At times, axons at the boundary of muscles 12 and 13 are not found, raising the possiblity that some have retracted. Occasionally, ectopic projections from neighboring nerves are found. However, those that form in unc-104¹⁷⁰ mutants do not have boutons. Consequently, both the normal innervation and the occasionally ectopic projection are incapable of normal morphogenesis.

unc-104¹⁷⁰ mutants do not exhibit any gross anatomical defects in the neuropil. However, the components of synaptic and dense-core vesicles are markedly redistributed in these mutants.

unc-104¹⁷⁰ mutant synapses exhibit fewer active zones compared to wild-type. They display only 11-24% of the puncta of wild-type, with 62% of the average intensity of wild-type. In addition, the puncta observed in unc-104¹⁷⁰ mutants occur along the axons rather than at the endings, where they are normally located. T-bars appear smaller than in wild-type and are less frequent.

unc-104[+]/unc-104¹⁷⁰ is an enhancer of abnormal neuroanatomy | pupal stage P5 phenotype of Df(3R)Exel7310/prd1^M56

unc-104[+]/unc-104¹⁷⁰ is an enhancer of abnormal size | pupal stage P5 phenotype of Df(3R)Exel7310/prd1^M56

unc-104[+]/unc-104¹⁷⁰ is an enhancer of dendritic tree | pupal stage P5 phenotype of Df(3R)Exel7310/prd1^M56

unc-104[+]/unc-104¹⁷⁰ is an enhancer of larval dorsal multidendritic neuron ddaC | pupal stage P5 phenotype of Df(3R)Exel7310/prd1^M56