Dickson, Dennis W.

Abstract Introduction We sought to determine whether a systems biology approach may identify novel late‐onset Alzheimer's disease (LOAD) loci. Methods We performed gene‐wide association analyses and integrated results with human protein‐protein interaction data using network analyses. We performed functional validation on novel genes using a transgenic Caenorhabditis elegans Aβ proteotoxicity model and evaluated novel genes using brain expression data from people with LOAD and other neurodegenerative conditions. Results We identified 13 novel candidate LOAD genes outside chromosome 19. Of those, RNA interference knockdowns of the C. elegans orthologs of UBC, NDUFS3, EGR1 , and ATP5H were associated with Aβ toxicity, and NDUFS3, SLC25A11, ATP5H , and APP were differentially expressed in the temporal cortex. Discussion Network analyses identified novel LOAD candidate genes. We demonstrated a functional role for four of these in a C. elegans model and found enrichment of differentially expressed genes in the temporal cortex.

Abstract Introduction Genetic loci for Alzheimer's disease (AD) have been identified in whites of European ancestry, but the genetic architecture of AD among other populations is less understood. Methods We conducted a transethnic genome‐wide association study (GWAS) for late‐onset AD in Stage 1 sample including whites of European Ancestry, African‐Americans, Japanese, and Israeli‐Arabs assembled by the Alzheimer's Disease Genetics Consortium. Suggestive results from Stage 1 from novel loci were followed up using summarized results in the International Genomics Alzheimer's Project GWAS dataset. Results Genome‐wide significant (GWS) associations in single‐nucleotide polymorphism (SNP)–based tests ( P < 5 × 10 −8 ) were identified for SNPs in PFDN1/HBEGF , USP6NL/ECHDC3 , and BZRAP1‐AS1 and for the interaction of the (apolipoprotein E) APOE ε4 allele with NFIC SNP. We also obtained GWS evidence ( P < 2.7 × 10 −6 ) for gene‐based association in the total sample with a novel locus, TPBG ( P = 1.8 × 10 −6 ). Discussion Our findings highlight the value of transethnic studies for identifying novel AD susceptibility loci.

ABSTRACTBackgroundThis study aimed to determine the frequency of transactive response DNA binding protein 43 kDa pathology in PSP, the clinical features of patients with this pathology, and genetic risk factors for it.MethodsHippocampal sections were screened with immunohistochemistry for transactive response DNA binding protein 43 kDa in 945 PSP cases. A subset of 261 cases that were negative in hippocampus was screened in the amygdala. The density and disruption of this pathology, as well as regional tau burden, and clinical and genetic characteristics were analyzed.ResultsWe observed transactive response DNA binding protein 43 kDa pathology in 47 cases in the hippocampus and an additional 9 cases that only affected the amygdala. Hippocampal sclerosis was the strongest risk factor, followed by Alzheimer's disease pathology, argyrophilic grain disease, and older age at death. Five stages of transactive response DNA binding protein 43 kDa pathology were identified in PSP: Stage A had pathology only in the amygdala (16%); stage I had pathology confined to the hippocampus and entorhinal cortex (9%); stage II included both regions of stage A and I (38%); stage III spread further to medial occipitotemporal gyrus (20%); and stage IV had pathology in the dorsolateral frontal lobe (18%). Anatomical areas vulnerable to PSP pathology had varying degrees of this pathology in stage II and later. PSP with transactive response DNA binding protein 43 kDa pathology were older at disease onset and had lower median MMSE scores; however, the latter was driven by concurrent pathologies.ConclusionsDistribution and clinical characteristics of transactive response DNA binding protein 43 kDa pathology in PSP were influenced by concurrent pathologies. This is the first study to observe that PSP‐vulnerable regions are also susceptible to this non‐tau pathology. © 2016 International Parkinson and Movement Disorder Society.

AbstractIntroductionWe hypothesized that common Alzheimer's disease (AD)‐associated variants within the triggering receptor expressed on myeloid (TREM) gene cluster influence disease through gene expression.MethodsExpression microarrays on temporal cortex and cerebellum from ∼400 neuropathologically diagnosed subjects and two independent RNAseq replication cohorts were used for expression quantitative trait locus analysis.ResultsA variant within a DNase hypersensitive site 5′ of TREM2, rs9357347‐C, associates with reduced AD risk and increased TREML1 and TREM2 levels (uncorrected P = 6.3 × 10−3 and 4.6 × 10−2, respectively). Meta‐analysis on expression quantitative trait locus results from three independent data sets (n = 1006) confirmed these associations (uncorrected P = 3.4 × 10−2 and 3.5 × 10−3, Bonferroni‐corrected P = 6.7 × 10−2 and 7.1 × 10−3, respectively).DiscussionOur findings point to rs9357347 as a functional regulatory variant that contributes to a protective effect observed at the TREM locus in the International Genomics of Alzheimer's Project genome‐wide association study meta‐analysis and suggest concomitant increase in TREML1 and TREM2 brain levels as a potential mechanism for protection from AD.

ABSTRACTBackgroundThe objectives of this study were to elucidate any potential association between α‐synuclein pathology and cognitive impairment and to determine the profile of cognitive impairment in multiple system atrophy (MSA) patients. To do this, we analyzed the clinical and pathologic features in autopsy‐confirmed MSA patients.MethodsWe retrospectively reviewed medical records, including neuropsychological test data, in 102 patients with autopsy‐confirmed MSA in the Mayo Clinic brain bank. The burden of glial cytoplasmic inclusions and neuronal cytoplasmic inclusions were semiquantitatively scored in the limbic regions and middle frontal gyrus. We also assessed concurrent pathologies potentially causing dementia including Alzheimer's disease, hippocampal sclerosis, and cerebrovascular pathology.ResultsOf 102 patients, 33 (32%) were documented to have cognitive impairment. Those that received objective testing, deficits primarily in processing speed and attention/executive functions were identified, which suggests a frontal‐subcortical pattern of dysfunction. Of these 33 patients with cognitive impairment, 8 patients had concurrent pathologies of dementia. MSA patients with cognitive impairment had a greater burden of neuronal cytoplasmic inclusions in the dentate gyrus than patients without cognitive impairment, both including and excluding patients with concurrent pathologies of dementia.ConclusionsThe cognitive deficits observed in this study were more evident on neuropsychological assessment than with cognitive screens. Based on these findings, we recommend that clinicians consider more in‐depth neuropsychological assessments if patients with MSA present with cognitive complaints. Although we did not identify the correlation between cognitive deficits and responsible neuroanatomical regions, a greater burden of neuronal cytoplasmic inclusions in the limbic regions was associated with cognitive impairment in MSA. © 2016 International Parkinson and Movement Disorder Society

AimThe p.P301L mutation in microtubule‐associated protein tau (MAPT) is a common cause of frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP‐17). We compare clinicopathologic features of five unrelated and three related (brother, sister and cousin) patients with FTDP‐17 due to p.P301L mutation.MethodsGenealogical, clinical, neuropathologic and genetic data were reviewed from eight individuals.ResultsThe series consisted of five men and three women with an average age of death of 58 years (52–65 years) and average disease duration of 9 years (3–14 years). The first symptoms were those of behavioural variant frontotemporal dementia in seven patients and semantic variant of primary progressive aphasia in one. Three patients were homozygous for the MAPT H1 haplotype; five had H1/H2 genotype. The apolipoprotein E genotype was ϵ3/ϵ3 in seven and ϵ3/ϵ4 in one. The average brain weight was 1015 g (876–1188 g). All had frontotemporal lobar or more diffuse cortical atrophy. Except for one patient, the hippocampus and parahippocampal gyrus had minimal atrophy, whereas there was atrophy of middle and inferior temporal gyri. Dentate fascia neuronal dispersion was identified in three patients, two of whom had epilepsy. In one patient there was extensive white matter tau involvement with Gallyas‐positive globular glial inclusions typical of globular glial tauopathy (GGT).ConclusionsThis clinicopathologic study shows inter‐ and intra‐familial clinicopathologic heterogeneity of FTDP‐17 due to MAPT p.P301L mutation, including GGT in one patient.