Dgrip79 resembles g‐tubulin interacting proteins but serves distinct functions

The centrosome plays a crucial role in the faithful transmission of chromosomes during cell division and serves as a nucleator and organizer of the microtubules that make up the mitotic spindle. Despite its indispensable function many aspects of centrosome biology remain unknown. An essential component of the centrosome is γ‐tubulin, which is required for microtubule nucleation. The Drosophila melanogaster γ ‐tubulin interacts with at least five additional proteins (Grips) to form a 'γ‐ tu bulin r ing c omplex' (γTuRC). The grips are related to one another by the presence of one or two regions of homology named 'grip motifs'. Grip motifs are rare: only seven grip‐containing proteins exist in the Drosophila genome. Because five of these are components of the γTuRC, it is possible that the grip motifs are somehow involved in γTuRC and/or centrosome function. To gain a better understanding of the function of the grip motif, we have begun to analyze the cell biology of Dgrip79, a 79kDa protein that contains both grip motifs. We show that Dgrip79 is expressed only in testes. In developing sperm, Dgrip79 localizes along the long axis of the nucleus, most likely associating with a bundle of microtubules of unknown function that runs along the length of the sperm head. Sucorse gradient analysis confirms that Dgrip79 is unlikely to be a part of the gTuRC. Together, our data suggest that Dgrip79 may be a microtubule binding protein involved in spermatogenesis. Grant Funding Source NSF