No abstract

IntroductionLate-onset Alzheimer's disease (LOAD, onset age > 60 years) is the most prevalent dementia in the elderly 1 , and risk is partially driven by genetics 2 . Many of the loci responsible for this genetic risk were identified by genome-wide association studies (GWAS) [3][4][5][6][7][8] . To identify additional LOAD risk loci, the we performed the largest GWAS to date (89,769 individuals), analyzing both common and rare variants. We confirm 20 previous LOAD risk loci and identify four new genome-wide loci (IQCK, ACE, ADAM10, and ADAMTS1). Pathway analysis of these data implicates the immune system and lipid metabolism, and for the first time tau binding proteins and APP metabolism. These findings show that genetic variants affecting APP and Aβ processing are not only associated with early-onset autosomal dominant AD but also with LOAD. Analysis of AD risk genes and pathways show enrichment for rare variants (P = 1.32 x 10 -7 ) indicating that additional rare variants remain to be identified. Main TextOur previous work identified 19 genome-wide significant common variant signals in addition to APOE 9 , that influence risk for LOAD. These signals, combined with 'subthreshold' common variant associations, account for ~31% of the genetic variance of LOAD 2 , leaving the majority of genetic risk uncharacterized 10 . To search for additional signals, we conducted a GWAS metaanalysis of non-Hispanic Whites (NHW) using a larger sample (17 new, 46 total datasets) from our group, the International Genomics of Alzheimer's Project (IGAP) (composed of four AD consortia: ADGC, CHARGE, EADI, and GERAD). This sample increases our previous discovery sample (Stage 1) by 29% for cases and 13% for controls (N=21,982 cases; 41,944 controls) ( Supplementary Table 1 and 2, and Supplementary Note). To sample both common and rare variants (minor allele frequency MAF ≥ 0.01, and MAF < 0.01, respectively), we imputed the discovery datasets using a 1000 Genomes reference panel consisting of . CC-BY-NC-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a 11 36,648,992 single-nucleotide variants, 1,380,736 insertions/deletions, and 13,805 structural variants. After quality control, 9,456,058 common variants and 2,024,574 rare variants were selected for analysis (a 63% increase from our previous common variant analysis in 2013).Genotype dosages were analyzed within each dataset, and then combined with meta-analysis ( Supplementary Figures 1 and 2 and Supplementary Table 3). The Stage 1 discovery metaanalysis was first followed by Stage 2 using the I-select chip we previously developed in Lambert et al (including 11,632 variants, N=18,845) and finally stage 3A (N=6,998). The final sample was 33,692 clinical AD cases and 56,077 controls.Meta-analysis of Stages 1 and 2 produced 21 associations with P ≤ 5x10 -8 (Table 1 and Figure 1). Of these, 18 were previously reported as genome-wide significant and three of them are signals not initially described in Lambert et al: the rare R47H TREM2 coding va...

The metaphase-anaphase transition is orchestrated through proteolysis of numerous proteins by an ubiquitin protein ligase called the Anaphase-promoting complex or cyclosome (APC/C) 1 . A crucial aspect of this process is sister chromatid separation, which is thought to be mediated by separase, a thiol protease activated by the APC/C. Separase cleaves cohesin, a ring-shaped complex that entraps sister DNAs 2, 3 . It is a matter of debate whether cohesin-independent forces also contribute to sister chromatid cohesion [4][5][6] . Using 4D-live-cell imaging of Drosophila syncytial embryos blocked in metaphase (via APC/C inhibition) we show that artificial cohesin cleavage 7 is sufficient to trigger chromosome disjunction. This is nevertheless insufficient for correct chromosome segregation. Kinetochore-microtubule attachments are rapidly destabilized by the loss of tension caused by cohesin cleavage in the presence of high Cyclin-dependent kinase 1 (Cdk1) activity, as occurs when the APC/C cannot destroy mitotic cyclins. Metaphase chromosomes undergo a bona-fide anaphase when cohesin cleavage is combined with Cdk1 inhibition. We conclude that only two key events, opening of cohesin rings and down regulation of Cdk1, are sufficient to drive proper segregation of chromosomes in anaphase.Correct attachment of sister DNAs to microtubules during mitosis depends on a force that actively holds them together. It is a matter of ongoing debate whether cohesin-independent forces (be they sister DNA concatenation [8][9][10][11] or proteinaceous linkages provided by ORC 12 or condensin 13 ) contribute to sister chromatid cohesion in metaphase cells [4][5][6] . If cohesin alone resists spindle forces prior to anaphase, then artificial opening the cohesin ring by an exogenous protease should trigger sister chromatid disjunction in the absence of separase activity. If, on the other hand, cohesin were just one of several mechanisms holding sisters together, then cleavage should not suffice. This key experiment has so far only been performed in yeast, where cleavage of cohesin's α-kleisin subunit by the Tobacco Etch virus protease (TEV) in cells arrested in metaphase initiates disjunction of most sister DNAs but not those of repetitive rDNAs within the nucleolus 14,15 . It is nevertheless argued that the larger chromosomes of animal and plant cells, or indeed other fungi, have very different properties. To address this, we used strains of the fruit fly D. melanogaster whose α-kleisin subunit Rad21 has been replaced by a version containing TEV cleavage sites (Rad21 TEV ) 7 . TEV protease injection causes catastrophic mitotic failure in syncytial embryos using Rad21 TEV ( Supplementary Information, Fig. S1). When injected before or during early stages of mitosis, it causes sister chromatids to disjoin as soon as the nuclear envelope breaks down. This precocious loss of sister chromatid cohesion is accompanied by aCorrespondence and requests for materials should be addressed to K.N. (kim.nasmyth@bioch.ox.ac.uk prometaphase delay...

A PAR-1–mediated bias in microtubule organization in the Drosophila oocyte underlies posterior-directed mRNA transport.

Localized mRNA translation is thought to play a key role in synaptic plasticity, but the identity of the transcripts and the molecular mechanism underlying their function are still poorly understood. Here, we show that Syncrip, a regulator of localized translation in the Drosophila oocyte and a component of mammalian neuronal mRNA granules, is also expressed in the Drosophila larval neuromuscular junction, where it regulates synaptic growth. We use RNA-immunoprecipitation followed by high-throughput sequencing and qRT-PCR to show that Syncrip associates with a number of mRNAs encoding proteins with key synaptic functions, including msp-300, syd-1, neurexin-1, futsch, highwire, discs large, and α-spectrin. The protein levels of MSP-300, Discs large, and a number of others are significantly affected in syncrip null mutants. Furthermore, syncrip mutants show a reduction in MSP-300 protein levels and defects in muscle nuclear distribution characteristic of msp-300 mutants. Our results highlight a number of potential new players in localized translation during synaptic plasticity in the neuromuscular junction. We propose that Syncrip acts as a modulator of synaptic plasticity by regulating the translation of these key mRNAs encoding synaptic scaffolding proteins and other important components involved in synaptic growth and function.