There is an increase in the total number of branches and the total number of boutons at the neuromuscular junction in mutant larvae compared to controls.
Overexpression by Scer\GAL4P2.4.Pdf results in a defasciculation phenotype of the termini of the LNv neuron's dorsal projections.
An ectopic collateral branch is observed on the small LNv projections in 6% of Fmr1EP3517 adult brains. The posterior tract of the LNv neurons shows a defasciculation phenotype in 22% of Fmr1EP3517 brains. These phenotypes are not observed in Fmr1EP3517/+ brains.
Slightly over 60% of homozygous Fmr1EP3517 mutants exhibit severe midline crossing in the β-lobe of the mushroom body (defined as a densely strained band equal to or greater in width and thickness than those of the adjacent β-lobes). Approximately just under 10% exhibit moderate midline crossing (defined as when the thickness of the fiber bundle crossing the midline is considerable but less than the width of the β-lobe termini). No sexual dimorphism in penetrance or expressivity is found.
Homozygous Fmr1EP3517 mutants exhibit misdirected or missing α-lobes in approximately 10% of cases.
Larvae expressing Fmr1EP3517 under the control of Scer\GAL4elav-C155 have significantly shorter synapses at the neuromuscular junction (70.0 +/- 3.6 μm) compared to wild-type larvae (111.1 μm).
Flies show no visible phenotypic abnormalities. When expression is driven by Scer\GAL4tim.PE, flies show arrhythmicity and period lengthening in a Scer\GAL4tim.PE-dependent manner.
Mutants show a fibre extension defect in the DC and LNv neurons. Extension of DC axons from the lobula to the medulla is incomplete, some axons show guidance errors. LNv neurons may over extend, show guidance defects or show aberrant morphology. The LVn defects are less consistent than those in the DC neurons. Stereotypical grid-like array of neurites entering the medulla is disrupted in mutant flies - short and thin branches fail to connect. This occurs even for neurons that do cross towards the distal medulla. Homozygotes show only 79.5% of expected eclosion from pupal case.
Mutants show no morphological defects. When tested for bang sensitivity, temperature sensitivity and phototaxis there is no detectable difference between wild type and mutant. However there are defects in coordination in a simple flight test. When expression is driven by Scer\GAL4hs.2sev a mild rough eye phenotype results.