GFP expression driven by the MtnA

promoter (AvicGFP^{Emerald.MtnA.MtnA-3'UTR}) is evident in cells that form a mesh-like structure surrounding the brain and in between the neuropiles. MtnA does not appear to be expressed at a discernible level in neurons, as the cells expressing GFP do not have dendrites or axonal processes. The shape and localization of the cells expressing GFP in the brain suggest that they are glia. Although we cannot be certain that MtnA expression is limited to the glia in the brain, our results provide direct evidence that MtnA is expressed in cell types other than the copper cells of the midgut and Malpighian tubules, as previously reported.