Fig. 2. Neuronal expression of Sra-1. Confocal images of mount preparations for Sra-1 expression (green) and axonal markers 24B10 or BP102 (red). The merge channel is shown on the right. (A) During embryogenesis Sra-1 (green) accumulates in the neuropile of the central nervous system, which also expresses the BP102 epitope. (B) In the optic ganglia of third instar larval brains Sra-1 protein expression can be detected in the medulla (md) and photoreceptor axons that traverse the lamina (la). An intense label can be seen in the termination zone of the photoreceptor axons R1-R6 in the lamina (star). The growth cones of these axons also express high levels of the 24B10 antigen (red). (C) Cell bodies of the photoreceptor neurons also express Sra-1, albeit at lower levels (arrowhead). ed, eye imaginal disc; os, optic stalk.