Longitudinal analyses revealed a significantly stronger decrease in CBF in frontal, temporal, parietal, and subcortical areas in the total group of mutation carriers and the GRN subgroup, with the strongest decrease in two mutation carriers who converted to clinical FTD during follow-up.
We describe a case of late onset frontotemporal dementia carrying the g.1977_1980 delCACT (Thr272fs) mutation in progranulin (GRN) gene, characterized by a positive family history for dementia and a clinical phenotype resembling dementia with Lewy bodies.
Progranulin (GRN) loss-of-function mutations leading to progranulin protein (PGRN) haploinsufficiency are prevalent genetic causes of frontotemporal dementia.
The generation of in vivo models of FTD involves either targeting genes with known disease-causative mutations such as GRN and C9orf72 or genes encoding proteins that form the inclusions that characterize the disease pathologically, such as TDP-43 and FUS.
Although CSF sTREM2 levels are not raised in FTD overall or in a particular clinical subtype of FTD, levels are raised in familial FTD associated with GRN mutations and in FTD syndromes due to AD pathology.
Among them, variants in the microtubule-associated protein tau (MAPT), GRN, and chromosome 9 open-reading frame 72 (C9orf72) genes are considered the major cause of FTD.
In this international, retrospective cohort study, we collected data on age at symptom onset, age at death, and disease duration for patients with pathogenic mutations in the GRN and MAPT genes and pathological expansions in the C9orf72 gene through the Frontotemporal Dementia Prevention Initiative and from published papers.
In this study, we used mouse models to investigate the role of neuronal and microglial progranulin insufficiency in the development of FTD-like pathology and behavioral deficits.
The discovery that heterozygous and homozygous mutations in the gene encoding progranulin are causally linked to frontotemporal dementia and lysosomal storage disease, respectively, reveals previously unrecognized roles of the progranulin protein in regulating lysosome biogenesis and function.
Importantly, this effect on GCase activity was rescued by treatment with saposin C. Together, these findings suggested that reduced GCase activity due to impaired processing of prosaposin may contribute to pathogenesis of FTD resulting from PGRN mutations.
The V363I variation was associated with frontotemporal dementia only in the proband which was also homozygous for the A allele of the progranulin single-nucleotide polymorphism rs9897526 and for methionine at codon 129 of the prion protein gene.
One hundred and sixty-seven mutation carriers (75 GRN, 60 C9orf72, and 32 MAPT) were included from the Genetic FTD Initiative (GENFI) study, a large international cohort of genetic FTD.
Further, we compared genotype-phenotype data of TBK1 carriers with frontotemporal dementia (n = 7), with those of frontotemporal dementia patients with a C9orf72 repeat expansion (n = 65) or a GRN mutation (n = 52) and with frontotemporal dementia patients (n = 259) negative for mutations in currently known causal genes.
Mutations in microtubule associated protein tau (MAPT), progranulin (GRN), chromosome 9 open-reading frame 72 (C9orf72) and CHCHD10 genes have been reported causing frontotemporal dementia (FTD) in different populations.