PARTIAL CHARACTERIZATION OF MURINE HUNTINGTIN AND APPARENT VARIATIONSIN THE SUBCELLULAR-LOCALIZATION OF HUNTINGTIN IN HUMAN, MOUSE AND RAT-BRAIN

Huntington's disease (HD) is an inherited neurodegenerative disorder c aused by the expansion of a CAG repeat in a gene coding for a protein of unknown function, We have raised a polyclonal antibody against a 12 amino acid peptide (residues 2110-2121 of human huntingtin) which spe cifically recognises huntingtin on Western blots of human, rat and mou se brain, We have characterised huntingtin expression in the mouse. Th e protein was detected on Western blots of all mouse tissues examined, with the highest expression seen in brain, Human, mouse and rat brain were fractionated by differential centrifugation and discontinuous Pe rcoll gradients. The fractions were analysed by Western blotting for h untingtin and synaptophysin (a synaptic vesicle localised protein). In mouse brain, huntingtin was localised in the soluble S3 fraction; in rat brain it was localised in the soluble S3 fraction and also in the membrane P2 and P3 fractions; in both normal and HD-affected human bra in, huntingtin was membrane bound with a distribution essentially the same as that of synaptophysin, These observed differences in the subce llular localisation of huntingtin between mouse and human brain are im portant in the context of mouse models for HD.