In the adult prothorax and neck, Syt1
immunoreactivity is observed in the type I boutons of motor neurons innervating the ventral cervical muscles, prothoracic sternal anterior rotator muscle 31, and prothoracic sternal adductor muscle 33, and in the type II boutons of motorneurons innervating ventral cervical muscle 27 and prothoracic sternal anterior rotator muscle 31. Type II boutons on muscle 31 that are along the cuticle lack Syt1
No protein is detected in the Syt1D27
mutant with a polyclonal antiserum against Syt1
protein is detected in the neuropil of the adult brain. It is observed in the synapse-rich regions in the lamina, the medulla, and the lobula. Staining is also observed in the neuropil in embryonic sections. In larvae, staining is observed at the neuromuscular junctions where it is tightly confined to the nerve terminals.
Immunocytochemical staining of whole mount embryos shows that Syt1
protein is rapidly transported to synapses and localizes to synaptic contact sites. In stage 14 embryos, the cell bodies of central nervous system neurons are transiently labeled. At stage 15, Syt1
protein is in the dorsal portion of the ventral nerve cord and in the brain. At stage 16, the longitudinal tracts of the central nervous system, motor neurons, and parts of the peripheral nervous system are stained. At stage 17, staining localizes to the longitudinal tracts of the central nervous system and to synapses in the body wall musculature. During larval development, Syt1
protein continues to be detected in neuromuscular junctions. Synaptic terminals in both type I and type II junctions stain. In the adult, Syt1
is detected in synapses of the adult head neuropil including those in the antennal lobes and the visual lamina.