%0 Journal Article %J J Alzheimers Dis %D 2016 %T A Novel Splice-Acceptor Site Mutation in GRN (c.709-2 A>T) Causes Frontotemporal Dementia Spectrum in a Large Family from Southern Italy. %A Sassi, Celeste %A Capozzo, Rosa %A Gibbs, Raphael %A Crews, Cynthia %A Zecca, Chiara %A Arcuti, Simona %A Copetti, Massimiliano %A Barulli, Maria R %A Brescia, Vincenzo %A Singleton, Andrew B %A Logroscino, Giancarlo %X

Heterozygous loss of function mutations in granulin represent a significant cause of frontotemporal lobar degeneration with ubiquitin and TDP-43 inclusions (FTLD-TDP). We report a novel GRN splice site mutation (c.709-2 A>T), segregating with frontotemporal dementia spectrum in a large family from southern Italy. The GRN c.709-2 A>T is predicted to result in the skipping of exon 8, leading to non-sense mediated mRNA decay. Moreover, the PGRN plasma levels in the GRN c.709-2 A>T carriers were significantly lower (24 ng/ml) compared to controls (142.7 ng/ml) or family members non-carriers (82.0 ng/ml) (p-value = 0.005, Kruskal Wallis), suggesting progranulin haploinsufficiency. We do not report any potential pathogenic GRN mutation in a follow-up cohort composed of 6 FTD families and 43 sporadic FTD cases, from the same geographic area. Our study suggests that GRN (c.709-2 A>T) is a novel and likely very rare cause of FTD in this Italian cohort. Finally, in line with previous studies, we show that GRN haploinsufficiency leads to a heterogeneous clinical picture, and plasma progranulin levels may be a reliable tool to identify GRN loss of function mutations. However, given that a) genetic and environmental factors, gender, and age may regulate PGRN plasma levels and b) plasma progranulin levels may not reflect PGRN levels in the central nervous system, we suggest that the measurement of progranulin in the plasma should always be coupled with genetic screening of GRN for mutations.

%B J Alzheimers Dis %V 53 %P 475-85 %8 2016 May 30 %G eng %N 2 %1 http://www.ncbi.nlm.nih.gov/pubmed/27258413?dopt=Abstract %R 10.3233/JAD-151170 %0 Journal Article %J N Engl J Med %D 2013 %T TREM2 variants in Alzheimer's disease. %A Guerreiro, Rita %A Wojtas, Aleksandra %A Bras, Jose %A Carrasquillo, Minerva %A Rogaeva, Ekaterina %A Majounie, Elisa %A Cruchaga, Carlos %A Sassi, Celeste %A Kauwe, John S K %A Younkin, Steven %A Hazrati, Lilinaz %A Collinge, John %A Pocock, Jennifer %A Lashley, Tammaryn %A Williams, Julie %A Lambert, Jean-Charles %A Amouyel, Philippe %A Goate, Alison %A Rademakers, Rosa %A Morgan, Kevin %A Powell, John %A St George-Hyslop, Peter %A Singleton, Andrew %A Hardy, John %K Aged %K Alzheimer Disease %K Animals %K Brain %K Exome %K Genetic Variation %K Genome-Wide Association Study %K Genotype %K Genotyping Techniques %K Heterozygote %K Humans %K Membrane Glycoproteins %K Mice %K Mice, Inbred A %K Mutation %K Receptors, Immunologic %K Risk Factors %K RNA, Messenger %K Sequence Analysis, DNA %X

BACKGROUND: Homozygous loss-of-function mutations in TREM2, encoding the triggering receptor expressed on myeloid cells 2 protein, have previously been associated with an autosomal recessive form of early-onset dementia.

METHODS: We used genome, exome, and Sanger sequencing to analyze the genetic variability in TREM2 in a series of 1092 patients with Alzheimer's disease and 1107 controls (the discovery set). We then performed a meta-analysis on imputed data for the TREM2 variant rs75932628 (predicted to cause a R47H substitution) from three genomewide association studies of Alzheimer's disease and tested for the association of the variant with disease. We genotyped the R47H variant in an additional 1887 cases and 4061 controls. We then assayed the expression of TREM2 across different regions of the human brain and identified genes that are differentially expressed in a mouse model of Alzheimer's disease and in control mice.

RESULTS: We found significantly more variants in exon 2 of TREM2 in patients with Alzheimer's disease than in controls in the discovery set (P=0.02). There were 22 variant alleles in 1092 patients with Alzheimer's disease and 5 variant alleles in 1107 controls (P<0.001). The most commonly associated variant, rs75932628 (encoding R47H), showed highly significant association with Alzheimer's disease (P<0.001). Meta-analysis of rs75932628 genotypes imputed from genomewide association studies confirmed this association (P=0.002), as did direct genotyping of an additional series of 1887 patients with Alzheimer's disease and 4061 controls (P<0.001). Trem2 expression differed between control mice and a mouse model of Alzheimer's disease.

CONCLUSIONS: Heterozygous rare variants in TREM2 are associated with a significant increase in the risk of Alzheimer's disease. (Funded by Alzheimer's Research UK and others.).

%B N Engl J Med %V 368 %P 117-27 %8 2013 Jan 10 %G eng %N 2 %1 http://www.ncbi.nlm.nih.gov/pubmed/23150934?dopt=Abstract %R 10.1056/NEJMoa1211851