Search

Neuromyelitis optica (NMO) is rare in Finland. To identify rare genetic variants contributing to NMO risk we performed whole exome, HLA and regulatory region sequencing in all ascertained cases during 2005-2013 (n=5) in a Southern Finnish population of 1.6 million. There were no rare variant shared by all patients. Four missense variants were shared by two patients in C3ORF20, PDZD2, C5ORF47 and ZNF606. Another PDZD2 variant was found in a third patient. In the non-coding sequence two predictably functional rare variants were shared by two patients. Our results do not support a homogeneous genetic etiology of NMO in Finland.

Objective Dementia with Lewy bodies is an α-synucleinopathy characterized by neocortical Lewy-related pathology (LRP). We carried out a genome-wide association study (GWAS) on neocortical LRP in a population-based sample of subjects aged 85 or over. Methods LRP was analyzed in 304 subjects in the Vantaa 85+ sample from Southern Finland. The GWAS included 41 cases with midbrain, hippocampal, and neocortical LRP and 177 controls without midbrain and hippocampal LRP. The Medical Research Council Cognitive Function and Ageing Study (CFAS) material was used for replication (51 cases and 131 controls). Results By analyzing 327,010 markers the top signal was obtained at the HLA-DPA1/DPB1 locus (P = 1.29 × 10−7); five other loci on chromosomes 15q14, 2p21, 2q31, 18p11, and 5q23 were associated with neocortical LRP at P

ObjectiveTo test the association of distinct neuropathologic features of Alzheimer disease (AD) with risk loci identified in genome-wide association studies.MethodsVantaa 85+ is a population-based study that includes 601 participants aged ≥85 years, of which 256 were neuropathologically examined. We analyzed 29 AD risk loci in addition to APOE ε4, which was studied separately and used as a covariate. Genotyping was performed using a single nucleotide polymorphism (SNP) array (341 variants) and imputation (6,038 variants). Participants with Consortium to Establish a Registry for Alzheimer Disease (CERAD) (neuritic Aβ plaques) scores 0 (n = 65) vs score M + F (n = 171) and Braak (neurofibrillary tangle pathology) stages 0–II (n = 74) vs stages IV–VI (n = 119), and with capillary Aβ (CapAβ, n = 77) vs without (n = 179) were compared. Cerebral amyloid angiopathy (CAA) percentage was analyzed as a continuous variable.ResultsAltogether, 24 of the 29 loci were associated (at p < 0.05) with one or more AD-related neuropathologic features in either SNP array or imputation data. Fifteen loci associated with CERAD score, smallest p = 0.0002122, odds ratio (OR) 2.67 (1.58–4.49) at MEF2C locus. Fifteen loci associated with Braak stage, smallest p = 0.004372, OR 0.31 (0.14–0.69) at GAB2 locus. Twenty loci associated with CAA, smallest p = 7.17E-07, β 14.4 (8.88–20) at CR1 locus. Fifteen loci associated with CapAβ smallest p = 0.002594, OR 0.54 (0.37–0.81) at HLA-DRB1 locus. Certain loci associated with specific neuropathologic features. CASS4, CLU, and ZCWPW1 associated only with CAA, while TREM2 and HLA-DRB5 associated only with CapAβ.ConclusionsAD risk loci differ in their association with neuropathologic features, and we show for the first time distinct risk loci for CAA and CapAβ.

ObjectiveTo characterize the clinical and neuropathologic features of patients with amyotrophic lateral sclerosis (ALS) with the superoxide dismutase 1 (SOD1) p.Ala90Val mutation, as well as the mutation frequency and the role of oligogenic mechanisms in disease penetrance.MethodsAn index patient with autopsy-proven ALS was discovered to have the SOD1 p.Ala90Val mutation, which was screened in 2 Finnish ALS cohorts (n = 453). Additional contributing variants were analyzed from whole-genome or whole-exome sequencing data.ResultsSeven screened patients (1.5%) were found to carry the SOD1 heterozygous mutation. Allele-sharing analysis suggested a common founder haplotype. Common clinical features included limb-onset, long disease course, and sensory symptoms. No TDP43 pathology was observed. All cases were apparently sporadic, and pedigree analysis demonstrated that the mutation has reduced penetrance. Analysis of other contributing genes revealed a unique set of additional variants in each patient. These included previously described rare ANG and SPG11 mutations. One patient was compound heterozygous for SOD1 p.Ala90Val and p.Asp91Ala.ConclusionsOur data suggest that the penetrance of SOD1 p.Ala90Val is modulated by other genes and indicates highly individual oligogenic basis of apparently sporadic ALS. Additional genetic variants likely contributing to disease penetrance were very heterogeneous, even among Finnish patients carrying the SOD1 founder mutation.

OBJECTIVES: Primary familial brain calcification (PFBC) is a rare neurological disease often inherited as a dominant trait. Mutations in four genes (SLC20A2, PDGFB, PDGFRB, and XPR1) have been reported in patients with PFBC. Of these, point mutations or small deletions in SLC20A2 are most common. Thus far, only one large deletion covering entire SLC20A2 and several smaller, exonic deletions of SLC20A2 have been reported. The aim of this study was to identify the causative gene defect in a Finnish PFBC family with three affected patients. MATERIALS AND METHODS: A Finnish family with three PFBC patients and five unaffected subjects was studied. Sanger sequencing was used to exclude mutations in the coding and splice site regions of SLC20A2, PDGFRB, and PDGFB. Whole-exome (WES) and whole-genome sequencing (WGS) were performed to identify the causative mutation. A SNP array was used in segregation analysis. RESULTS: Copy number analysis of the WGS data revealed a heterozygous deletion of ~578 kb on chromosome 8. The deletion removes the 5' UTR region, the noncoding exon 1 and the putative promoter region of SLC20A2 as well as the coding regions of six other genes. CONCLUSIONS: Our results support haploinsufficiency of SLC20A2 as a pathogenetic mechanism in PFBC. Analysis of copy number variations (CNVs) is emerging as a crucial step in the molecular genetic diagnostics of PFBC, and it should not be limited to coding regions, as causative variants may reside in the noncoding parts of known disease-associated genes.

Nasu-Hakola disease (NHD) is a rare autosomal recessive disease that is characterized by cyst-like bone lesions and pathologic fractures combined with an early-onset frontal type of dementia. Mutations in DNAX-activation protein 12 (DAP12) and triggering receptor expressed on myeloid cells 2 (TREM2) are the known genetic causes of NHD. However, the role of both these genes in the neurodegenerative process is still partly unclear, and the input of other modifying factors has been postulated. Frontotemporal lobar degeneration (FTLD) is a neuropathologically and genetically heterogeneous neurodegenerative disease. A hexanucleotide repeat expansion in the chromosome 9-associated open reading frame 72 (C9ORF72) gene is the most common cause of familial FTLD in Finland. Here, we describe a family with 3 siblings with a clinical diagnosis of NHD. All patients had an equivalent age of onset of the behavioral/cognitive symptoms, and brain imaging revealed a similar pattern of brain atrophy and calcification in putamen and caudate nucleus. Case II-3 had the most severe phenotype with epilepsy and a rapid cognitive decline. Genetic analyses were performed in 2 patients (cases II-2 and II-3), and both had a homozygous DAP12 deletion. Because the role of DAP12 and TREM2 in neurodegeneration in NHD is partly unclear, our aim was to evaluate the role of other genetic variations as modifiers. The C9ORF72 expansion was found in case II-2. Exome sequencing did not reveal any other mutations that could be involved in FTLD. Case II-3 had a novel predictably deleterious mutation in the progressive myoclonic epilepsy type 2 (EPM2), which may have influenced his epilepsy as the EPM2 has been implicated in Lafora progressive myoclonic epilepsy. We conclude that the C9ORF72 expansion is probably an incidental finding because it did not have any apparent influence on the phenotype. Exome sequencing identified several rare missense variants and indels. Additional analyses in other NHD patients will be needed to elucidate their clinical relevance.