Citations

AbstractFrontotemporal lobar degeneration (FTLD) is the second leading cause of dementia in individuals under age 65. In many patients, the predominant pathology includes neuronal cytoplasmic or intranuclear inclusions of ubiquitinated TAR DNA binding protein 43 (FTLD‐TDP). Recently, a genome‐wide association study identified the first FTLD‐TDP genetic risk factor, in which variants in and around the TMEM106B gene (top SNP rs1990622) were significantly associated with FTLD‐TDP risk. Intriguingly, the most significant association was in FTLD‐TDP patients carrying progranulin (GRN) mutations. Here, we investigated to what extent the coding variant, rs3173615 (p.T185S) in linkage disequilibrium with rs1990622, affects progranulin protein (PGRN) biology and transmembrane protein 106 B (TMEM106B) regulation. First, we confirmed the association of TMEM106B variants with FTLD‐TDP in a new cohort of GRN mutation carriers. We next generated and characterized a TMEM106B‐specific antibody for investigation of this protein. Enzyme‐linked immunoassay analysis of progranulin protein levels showed similar effects upon T185 and S185 TMEM106B over‐expression. However, over‐expression of T185 consistently led to higher TMEM106B protein levels than S185. Cycloheximide treatment experiments revealed that S185 degrades faster than T185 TMEM106B, potentially due to differences in N‐glycosylation at residue N183. Together, our results provide a potential mechanism by which TMEM106B variants lead to differences in FTLD‐TDP risk. image We studied the p.T185S TMEM106B genetic variant previously implicated in frontotemporal dementia with TAR DNA binding protein 43 pathology caused by progranulin mutations. Our cell culture studies provide evidence that the protective S185 isoform is degraded more rapidly than T185 TMEM106B, potentially due to differences in glycosylation. These findings suggest that low TMEM106B levels might protect against FTLD‐TDP in these patients.

AbstractObjectiveA National Institute on Aging–sponsored work group on preclinical Alzheimer's disease (AD) articulated the need to characterize cognitive differences between normal aging and preclinical AD.MethodsSeventy‐one apolipoprotein E (APOE) ε4 homozygotes, 194 ε3/ε4 heterozygotes, and 356 ε4 noncarriers age 21 to 87 years who were cognitively healthy underwent neuropsychological testing every 2 years. Longitudinal trajectories of test scores were compared between APOE subgroups.ResultsThere was a significant effect of age on all cognitive domains in both APOE ε4 carriers and noncarriers. A significant effect of APOE ε4 gene dose was confined to the memory domain and the Dementia Rating Scale. Cross‐sectional comparisons did not discriminate the groups.ConclusionsAlthough cognitive aging patterns are similar in APOE ε4 carriers and noncarriers, preclinical AD is characterized by a significant ε4 gene dose effect that impacts memory and is detectable longitudinally. Preclinical neuropsychological testing strategies should emphasize memory‐sensitive measures and longitudinal design.

Abstract Objective Behçet's disease ( BD ) is a chronic, relapsing, inflammatory vascular disease with no pathognomonic test. Low sensitivity of the currently applied International Study Group ( ISG ) clinical diagnostic criteria led to their reassessment. Methods An International Team for the Revision of the International Criteria for BD (from 27 countries) submitted data from 2556 clinically diagnosed BD patients and 1163 controls with BD ‐mimicking diseases or presenting at least one major BD sign. These were randomly divided into training and validation sets. Logistic regression, ‘leave‐one‐country‐out’ cross‐validation and clinical judgement were employed to develop new International Criteria for BD ( ICBD ) with the training data. Existing and new criteria were tested for their performance in the validation set. Results For the ICBD , ocular lesions, oral aphthosis and genital aphthosis are each assigned 2 points, while skin lesions, central nervous system involvement and vascular manifestations 1 point each. The pathergy test, when used, was assigned 1 point. A patient scoring ≥4 points is classified as having BD . In the training set, 93.9% sensitivity and 92.1% specificity were assessed compared with 81.2% sensitivity and 95.9% specificity for the ISG criteria. In the validation set, ICBD demonstrated an unbiased estimate of sensitivity of 94.8% (95% CI : 93.4–95.9%), considerably higher than that of the ISG criteria (85.0%). Specificity (90.5%, 95% CI : 87.9–92.8%) was lower than that of the ISG ‐criteria (96.0%), yet still reasonably high. For countries with at least 90%‐of‐cases and controls having a pathergy test, adding 1 point for pathergy test increased the estimate of sensitivity from 95.5% to 98.5%, while barely reducing specificity from 92.1% to 91.6%. Conclusion The new proposed criteria derived from multinational data exhibits much improved sensitivity over the ISG criteria while maintaining reasonable specificity. It is proposed that the ICBD criteria to be adopted both as a guide for diagnosis and classification of BD .

Sortilin 1 regulates the levels of brain progranulin (PGRN), a neurotrophic growth factor that, when deficient, is linked to cases of frontotemporal lobar degeneration with TAR DNA-binding protein-43 (TDP-43)–positive inclusions (FTLD-TDP). We identified a specific splicing enhancer element that regulates the inclusion of a sortilin exon cassette (termed Ex17b) not normally present in the mature sortilin mRNA. This enhancer element is consistently present in sortilin RNA of mice and other species but absent in primates, which carry a premature stop codon within the Ex17b sequence. In the absence of TDP-43, which acts as a regulatory inhibitor, Ex17b is included in the sortilin mRNA. In humans, in contrast to mice, the inclusion of Ex17b in sortilin mRNA generates a truncated, nonfunctional, extracellularly released protein that binds to but does not internalize PGRN, essentially acting as a decoy receptor. Based on these results, we propose a potential mechanism linking misregulation of sortilin splicing with altered PGRN metabolism.