Association of the Variant Cys139Arg at GRN Gene to the Clinical Spectrum of Frontotemporal Lobar Degeneration

Background: Progranulin protein (PGRN) is a cysteine-rich growth factor encoded by the progranulin gene (GRN). PGRN mutations were identified in patients with frontotemporal lobar degeneration (FTLD) and recently its role as risk factor has been described in patients with probable Alzheimer's disease (AD). To date, more than 100 genetic variants in GRN gene have been described and the pathogenic nature is still unclear for almost 36% of them. Objective: Here, we describe three clinical cases carrying the PGRN variation Cys139Arg in order to increase the knowledge on the association of this variant to the clinical spectrum of FTLD. Methods: The genetic analysis was performed using high resolution melting analysis. The Human Progranulin ELISA Kit was used in order to determine PGRN expression levels in the plasma samples. Results: The three patients carrying the genetic variation showed three final different clinical diagnosis, respectively behavioral frontotemporal dementia, semantic dementia, and corticobasal syndrome, thus underlining the clinical heterogeneity typically associated with GRN mutations. All cases shared similar plasma PGRN levels that resulted intermediate between those measured in controls and in GRN null mutation carriers, showing a partial reduction of the protein in plasma. Moreover, according to the bioinformatics software, the Cys139Arg variation causes a decreased stability of the structure of the protein. Conclusion: We describe three new patients affected by neurological syndromes included in the clinical spectrum of FTLD carrying the Cys139Arg genetic variant, thus suggesting a possible implication in the pathogenesis of FTLD.