trio^E4.1/Df(3L)Fpa1 embryos show disruption of Fas2-positive longitudinal fascicles; the outermost fascicles are discontinuous and fused to the adjacent inner fascicles.

Heterozygotes with Df(3L)Fpa1 die during the larval stages. Gross morphology of larvae is wild type but central nervous system show defects in axon patterning. Outermost fascicle of the longitudinal connectives show gaps, fusion with inner fascicles and misrouting. ISNb shows stall and fusion phenotypes, though these phenotypes are not as pronounced as the CNS phenotype. In trio^S036810/trio^E4.1 the LV and LM lobes of the mushroom bodies are abnormally developed. In the adult mushroom bodies the α, β abd γ lobes are altered. The ellipsoid body is also affected, with variable severity. The axons extend to the correct region but fail to form their arborization pattern. Clonal analysis in the mushroom body revealed that the abnormal neurite projection phenotype is largely cell autonomous. Mutant axons navigate normally through the peduncle to the region of bifurcation but do not reach the vertical and medial lobes.