Neuromuscular junctions (NMJs) of Ank2^E380/Ank2^K327 larvae have fewer but larger boutons than normal. The presynaptic endings often appear grossly enlarged. The synaptic span (the widest extension of synaptic branches along a muscle fibre) is reduced compared to wild type. Ultrastructurally, the number and morphology of mitochondria appears relatively normal, while there is a slight reduction in the thickness of the subsynaptic reticulum and a higher frequency of large "clear" vesicles and multivesicular bodies than normal. The mutant NMJs have large continuous presynaptic cavities which completely lack the "bottleneck" regions (thin axonal connections between bouton cavities) found in wild-type.

Tubulin accumulations are seen to fill entire boutons in some Ank2^E380/Ank2^K327 larval NMJs. These accumulations resemble axonal retraction bulbs, and usually occur at the end of microtubule cables.

The microtubule cytoskeleton appears structurally normal in the peripheral nerves of Ank2^E380/Ank2^K327 larvae. However, the distribution of synaptic vesicles is abnormal, with clusters of vesicles being present in the mutant peripheral nerves.

Ank2^K327/Ank2^RM5-1 larvae show defects in expansion of synaptic branches at the NMJ during larval development, with no outgrowth or even retraction occurring in 66% of mutant NMJs between muscles 6/7 from early second to third instar, compared to no expansion being seen in only 12% of control NMJs during this period.

Ank2^E380/Ank2^K327 larvae show a decrease in the number of synaptic boutons/muscle area along the anterior-posterior axis, in contrast to wild type.