Identification and characterization of the disease gene for autosomal dominant spastic paraplegia linked to chromosome 14q (SPG3)
Final Report Abstract
After the identification of atlastin-1 as the SPG3A disease gene we were able to assign mutations to the three large pedigrees which lead originally to the SPG3A locus. The F151S mutation found in the German pedigree remains up to now the most N-terminal mutation ever found. The mutation R239C was found in one of our French pedigrees, as well as in many other families before and after our publication. We looked into the reason for this uniquely high mutation frequency and found that both the existence of a mutation hot spot and a founder effect might contribute to it. The S398Y mutation found in the second French pedigree destroys a possible target for protein kinase C phosphorylation outside the GTPase domain. We have created an antibody specifically recognizing human atlastin-1 N-terminus, which we would like to put to everyone's disposal, who is interested in studying the SPG3A pathomechanism. However, it should be mentioned that the N-terminal atlastin-1 antibody created in Craig Blackstone's laboratory might be the better choice because of its higher sensitivity and its applicability to both human and murine tissue. As described by other research teams, when over-expressed in mammalian cells atlastin-1 colocalized mainly with the endoplasmic reticulum. We succeeded in producing purified soluble GST atlastin-1 fusion protein, with GST tagged to the N-terminus of the full-length or truncated protein. However, this protein failed to exhibit any significant enzymatic GTPase activity in in-vitro assays. A commercially performed yeast-2-hybrid screening revealed no interactors for full-length atlastin-1 or its N-terminal fragments. However, it suggested the possible interaction of the C-terminus with TRAX (translin interacting factor X). Unfortunately, further investigation with co-localization and co-immunprecipitation studies could not corroborate an interaction between atlastin-1 and this well characterized protein, which presumably plays a role in the transport and metabolism of dendritic niRNA, a site often discussed for spastic paraplegia pathogenesis. The output of significant results from these three years of research work, which contributes to the understanding of SPG3 pathogenesis is long way behind our own expectations.
Publications
- (2004) Early onset autosomal dominant spastic paraplegia caused by novel mutations in SPG3A. Neurogenetics 5: 239-243
Abel A, Fonknechten N, Hofer A, Dürr A, Cruaud C, Voit T, Weissenbach J, Brice A, Klimpe S, Auburger G, Hazan J
