Genetic mechanisms in primary dystonia

The molecular and genetic mechanisms involved in the pathogenesis of primary dystonia were investigated. This was carried out with two core studies. The pathogenesis of DYT1 dystonia was examined by the creation of a cell model. A single amino acid deletion in the DYT1 gene, which codes for a protein called torsinA, is responsible for most cases of primary, early-onset, generalized torsion dystonia. The gene in its wildtype and mutant forms were transfected into HEK 293 cells and the proteins locations and associations were studied. Wildtype torsinA was found to reside in the endoplasmic reticulum (ER). Mutant torsinA, however, was found in the nuclear envelope (NE) and in perinuclear inclusions that were not associated with the endoplasmic reticulum. In SH-SY5Y cells these inclusions were found to be associated with vesicular monoamine transporter type 2 (VMAT2), a transmembrane protein responsible for packaging catecholamine into vesicles. This association was studied in greater detail by immunoprecipitation and the functional implications were investigated by dopamine release experiments. The ultrastructure of the inclusions was also investigated by electron microscopy. Cervical dystonia and blepharospasm are the most common forms of focal primary dystonia. Most cases are apparently sporadic, although familial cases have been described. An allelic association study of genes involved in dopamine neurotransmission was carried out in order to determine whether genetic factors might contribute to an individual’s susceptibility to developing dystonia. An allele near the dopamine receptor 5 (DRD5) gene was found to be associated with cervical dystonia and blepharospasm. The presence of a causative mutation in the DRD5 gene was investigated by restriction fragment length polymorphism (RFLP) analysis and by sequencing