a melanogaster 19271755 is widely used in neurodegenerative diseases research. In particular, several fly strains have been generated to model Huntington’s disease, a dominantly inherited neurodegenerative disorder caused by an abnormal polyglutamine expansion in the huntingtin protein. These models are based on the overexpression of the full length, or Nterminal fragments of, human HTT. Flies expressing mutant HTT show neuronal dysfunction, such as defects in synaptic transmission and axonal transport, neuronal degeneration, locomotor deficits and shorter lifespans. HD fly models have been extensively used to validate candidate approaches and to search for gene modifiers that rescue neurodegeneration. Importantly, these studies are based on the notion that the mutation in HTT results in a gain of new toxic functions that are unrelated to wild-type HTT function. Indeed, the HD mutation is dominant and the overexpression of the HTT fragments containing the polyQ expansion is sufficient to induce phenotypes in flies. MedChemExpress MEK162 However, recent evidence in mammals suggests that alteration of the wild-type HTT 
functions also contributes to HD. This duality, both gain and loss of function, of the pathogenic mechanisms raises the issues of whether the overexpression of polyQ HTT in flies faithfully recapitulates mammalian HD, and the degree to which HTT function is conserved between flies and mammals. HTT is a large scaffold protein of 350 kDa in human and of a predicted 400 kDa in fly. HTT interacts with hundreds of proteins and regulates several cellular functions. For example, laboratories have reported that HTT is a positive regulator of microtubule–based transport. This function is altered upon polyQ expansion and vesicular transport is slowed down as a result. Three studies have investigated the function of Drosophila HTT in axonal transport but there are discrepancies between their findings. Silencing DmHTT by sh-RNA resulted in accumulation of axonal organelles, characteristic of 1 Huntingtin’s Function in Flies severe transport defects. This phenotype was more evident in kinesin heavy chain heterozygous flies. By contrast, the second study reported that HTT knock-out flies are viable with no obvious developmental defects and normal axonal transport: no synaptotagmin accumulation was observed in axons. However, neither study directly assessed the dynamic nature of vesicles in axons through the observation of fluorescent cargo by videomicroscopy. Importantly, in mammals, in contrast to the silencing or depletion of molecular motors, HTT silencing reduces but 7986199 does not totally block axonal transport of cargo and does not result in the accumulation of axonal organelles. Finally, a recent study reported a defect in the dynamics of Rab11 but not Rab5 vesicles in Drosophila larvae in which DmHTT was silenced by RNAi. These results suggest that DmHTT could play an important role in flies. Here, we report the study, by various complementary approaches, of the role of HTT in fast axonal transport. Our results indicate that the function of HTT in axonal transport is evolutionarily conserved between flies and mammals. Immunoprecipitation was performed with mMACS GFP-Tagged Protein Isolation Kit according to the provided protocol. Anti-HA beads were used as negative controls. Microtubule Depolymerization-Repolymerization Assay HEK 293 cells where lyzed by passing the samples 10 times in a 15 G syringe in ice cold BRB80 buffer containing a cocktail of protease inhibi
