Such a situation was, for example, observed by studying the human mutation R183Q in the pitrilysin metallopeptidase 1 encoded by PITRM1 in yeast, taking advantage of the presence of the orthologous gene, CYM1. This autosomal recessive missense mutation, associated with protein instability, was found in two patients presenting a slowly progressive neurodegenerative disease characterised by mental retardation, spinocerebellar ataxia, cognitive decline and psychosis [68]. Here, PITRM1 is linked to cerebellar ataxia.