Meta-analysis of existing genome-wide association studies on Alzheimer's disease (AD) showed subgenome-wide association of an intronic variant in the sequestosome 1 (SQSTM1) gene with AD. We performed targeted resequencing of SQSTM1 in Flanders-Belgian AD patients selected to be enriched for a genetic background (n = 435) and geographically matched nonaffected individuals (n = 872) to investigate the role of both common and rare SQSTM1 variants. Results were extended to the European early-onset dementia cohorts (926 early-onset Alzheimer's disease [EOAD] patients and 1476 nonaffected individuals). Of the 61 detected exonic variants in SQSTM1, the majority were rare (n = 57). Rare variant (minor allele frequency <0.01) burden analysis did not reveal an increased frequency of rare variants in EOAD patients in any of the separate study populations nor when meta-analyzing all cohorts. Common variants p.D292= and p.R312= showed nominal association with AD (odds ratiop.D292= = 1.11 [95% confidence interval = 1-1.22], p = 0.04), only when including the Flanders-Belgian cohort in the meta-analysis. We cannot exclude a role of SQSTM1 genetic variability in late-onset AD, but our data indicate that SQSTM1 does not play a major role in the etiology of EOAD.

Mutations in the gene coding for Sequestosome 1 (SQSTM1) have been genetically associated with amyotrophic lateral sclerosis (ALS) and Paget disease of bone. In the present study, we analyzed the SQSTM1 coding sequence for mutations in an extended cohort of 1,808 patients with frontotemporal lobar degeneration (FTLD), ascertained within the European Early-Onset Dementia consortium. As control dataset, we sequenced 1,625 European control individuals and analyzed whole-exome sequence data of 2,274 German individuals (total n = 3,899). Association of rare SQSTM1 mutations was calculated in a meta-analysis of 4,332 FTLD and 10,240 control alleles. We identified 25 coding variants in FTLD patients of which 10 have not been described. Fifteen mutations were absent in the control individuals (carrier frequency <0.00026) whilst the others were rare in both patients and control individuals. When pooling all variants with a minor allele frequency <0.01, an overall frequency of 3.2 % was calculated in patients. Rare variant association analysis between patients and controls showed no difference over the whole protein, but suggested that rare mutations clustering in the UBA domain of SQSTM1 may influence disease susceptibility by doubling the risk for FTLD (RR = 2.18 [95 % CI 1.24-3.85]; corrected p value = 0.042). Detailed histopathology demonstrated that mutations in SQSTM1 associate with widespread neuronal and glial phospho-TDP-43 pathology. With this study, we provide further evidence for a putative role of rare mutations in SQSTM1 in the genetic etiology of FTLD and showed that, comparable to other FTLD/ALS genes, SQSTM1 mutations are associated with TDP-43 pathology.