The cis-Golgi Drosophila GMAP has a role in anterograde transport and Golgi organization in vivo, similar to its mammalian ortholog in tissue culture cells

The Golgi microtubule-associated protein of 210 kDa (GMAP-210) has been shown to play a role in the assembly and maintenance of the Golgi apparatus in mammalian tissue culture cells. To develop a genetic model to study the function of GMAP-210 in vivo, we identified its closest relative in Drosophila melanogaster, dGMAP. We show that the dGMAP gene encodes two alternatively spliced transcripts, only one of which is translated into a protein product. To gain insight into the role of dGMAP, we generated a polyclonal antibody and investigated the protein distribution during development. This gene is ubiquitously expressed during embryonic and larval development with the highest level in polar cells, gut and salivary glands. We further show that dGMAP is present in the Golgi apparatus, and using electron microscopy of salivary glands, we observed a preferential localization at the cis side and at the rims of the Golgi stacks. Finally, we demonstrate that overexpression of dGMAP in salivary glands impairs Golgi architecture and function, whereas RNAi-mediated depletion of dGMAP does not induce any structural modification of the Golgi apparatus, and anterograde transport is seemingly unaffected. Altogether our results suggest that dGMAP is the ortholog of mammalian GMAP-210. (c) 2006 Elsevier GmbH. All rights reserved.