New insights into the genetic etiology of Alzheimer's disease and related dementias.

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Analysis of shared heritability in common disorders of the brain

Paroxysmal Cerebral Disorder

Exome sequencing identifies rare damaging variants in ATP8B4 and ABCA1 as risk factors for Alzheimer’s disease

Alzheimer’s disease (AD), the leading cause of dementia, has an estimated heritability of approximately 70%1. The genetic component of AD has been mainly assessed using genome-wide association studies, which do not capture the risk contributed by rare variants2. Here, we compared the gene-based burden of rare damaging variants in exome sequencing data from 32,558 individuals—16,036 AD cases and 16,522 controls. Next to variants in TREM2, SORL1 and ABCA7, we observed a significant association of rare, predicted damaging variants in ATP8B4 and ABCA1 with AD risk, and a suggestive signal in ADAM10. Additionally, the rare-variant burden in RIN3, CLU, ZCWPW1 and ACE highlighted these genes as potential drivers of respective AD-genome-wide association study loci. Variants associated with the strongest effect on AD risk, in particular loss-of-function variants, are enriched in early-onset AD cases. Our results provide additional evidence for a major role for amyloid-β precursor protein processing, amyloid-β aggregation, lipid metabolism and microglial function in AD

Ultrafast optical Stark mode-locked semiconductor laser

We report on 260 fs transform-limited pulses generated directly by an optical Stark passively mode-locked semiconductor disk laser at a 1 GHz repetition rate. A surface recombination semiconductor saturable absorber mirror and a step-index gain structure are used. Numerical propagation modeling of the optical Stark effect confirms that this mechanism is able to form the pulses that we observe

Exome sequencing identifies rare damaging variants in the ATB8B4 and ABCA1 genes as novel risk factors for Alzheimer's disease

BACKGROUND: Damaging rare variants in the TREM2, SORL1 and ABCA7 genes have been associated with an increased risk of developing Alzheimer's Disease (AD) with odds ratios that were not observed since the identification of the main AD genetic risk factor, the APOE-ε4 allele. Here, we aimed to identify additional AD-associated genes by investigating the burden of rare damaging variants in the exomes of AD cases and controls. METHOD: On a single server, we analyzed in two stages, the data from 52,270 exome sequences from several independent datasets from Europe and the United States. After comprehensive QC, Stage-1 and Stage-2 datasets comprised in total 16,396 AD cases (5,672 EOAD) and 18,107 controls with European ancestry. All detected non-synonymous and loss-of-function rare variants were prioritized by REVEL and LOFTEE, and analyzed in a per-gene burden analysis. After a Stage-1 discovery analysis, we replicated findings in an independent dataset (Stage-2). We combined the Stage-1 and Stage-2 datasets and determined, for each gene, the features of the variants that drive the burden-associations. RESULTS: We confirmed the AD-association of rare damaging variants SORL1, TREM2, ABCA7, and newly identified a significant AD-association of rare damaging variants in the ATP8B4 and ABCA1 genes. In addition, we find a strong indication for the AD-association of ADAM10 and SRC genes (Stage-2 p<0.05). For most genes, we observed a larger effect size for LOF variants compared to missense variants (Figure-A). High-impact variants in these genes are mostly extremely rare and enriched in AD patients with early ages at onset (Figure-B). CONCLUSION: We identified, for the first time, the AD-association of rare damaging variants in two genes: (i) microglial ATP8B4 which is involved in phospholipid transport, and (ii) ABCA1 which plays a critical role in lipidation of apoE thereby supporting Aβ processing. Further, we found strong evidence for the AD-association of damaging variants in ADAM10 and SRC genes. ADAM10 is involved in the proteolytic processing of APP, while SRC is a Non-Receptor Tyrosine Kinase which binds PTK2B/Pyk2, a known AD risk factor. Together, our study provides further evidence for the role of Aβ and microglia in AD pathophysiology