Alzheimer's disease is characterized by a widespread functional disturbance of the human brain. Fibrillar amyloid proteins are deposited inside neurons as neurofibrillary tangles and extracellularly as amyloid plaque cores and in blood vessels. The major protein subunit (A4) of the amyloid fibril of tangles, plaques and blood vessel deposits is an insoluble, highly aggregating small polypeptide of relative molecular mass 4,500. The same polypeptide is also deposited in the brains of aged individuals with trisomy 21 (Down's syndrome). We have argued previously that the A4 protein is of neuronal origin and is the cleavage product of a larger precursor protein. To identify this precursor, we have now isolated and sequenced an apparently full-length complementary DNA clone coding for the A4 polypeptide. The predicted precursor consists of 695 residues and contains features characteristic of glycosylated cell-surface receptors. This sequence, together with the localization of its gene on chromosome 21, suggests that the cerebral amyloid deposited in Alzheimer's disease and aged Down's syndrome is caused by aberrant catabolism of a cell-surface receptor.

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SUMMARY Despite a wealth of clinical data showing an association between inflammation and degenerative disorders in elderly, the immune sensors that causally link systemic inflammation to aging remain unclear. Here we detail a mechanism that the Nlrp3 inflammasome controls systemic low grade age-related ‘sterile’ inflammation in both periphery and brain independently of the non-canonical caspase-11 inflammasome. Ablation of Nlrp3 inflammasome protected mice from age-related increases in the innate immune activation, alterations in CNS transcriptome and astrogliosis. Consistent with the hypothesis that systemic low grade inflammation promotes age-related degenerative changes, the deficient Nlrp3 inflammasome mediated caspase-1 activity improved glycemic control and attenuated bone loss and thymic demise. Notably, IL-1 mediated only Nlrp3 inflammasome dependent improvement in cognitive function and motor performance in aged mice. These studies reveal Nlrp3 inflammasome as an upstream target that controls age-related inflammation and offer innovative therapeutic strategy to lower Nlrp3 activity to delay multiple age-related chronic diseases.

Background The prevalence of mental illness, particularly depression and dementia, is increased by obesity. Here we test the hypothesis that obesity-associated changes in gut microbiota are intrinsically able to impair neurocognitive behavior in mice. Methods Conventionally housed, non-obese, adult male C57BL/6 mice maintained on a normal chow diet were subjected to a microbiome depletion/transplantation paradigm using microbiota isolated from donors (given) on either high-fat (HFD) or control diet (CD). Following recolonization, mice were subjected to comprehensive behavioral and biochemical analyses. Results The mice given HFD microbiota had significant and selective disruptions in exploratory, cognitive, and stereotypical behavior compared to mice with CD microbiota in the absence of significant differences in body weight. Sequencing-based phylogenetic analysis confirmed the presence of distinct core microbiota between groups, with alterations in α- and β- diversity, modulation in taxonomic distribution, and statistically significant alterations to metabolically active taxa. HFD microbiota also disrupted markers of intestinal barrier function, increased circulating endotoxin, and increased lymphocyte expression of Iba1, TLR2, and TLR4. Finally, evaluation of brain homogenates revealed that HFD-shaped microbiota increased neuroinflammation and disrupted cerebrovascular homeostasis. Conclusions Collectively, these data reinforce the link between gut dysbiosis and neurologic dysfunction and suggest that dietary and/or pharmacological manipulation of gut microbiota could attenuate the neurologic complications of obesity.

Promoter features related to tissue-specific expression

A genome-wide analysis of promoters was carried out in the context of gene expression patterns in tissue surveys using human microarray and EST-based expression data. The study revealed that most genes show statistically significant tissue-dependent variations of expression level and identified components of promoters that distinguish tissue-specific from ubiquitous genes.

Sheep are the natural hosts of the pathogens that cause scrapie, an infectious degenerative disease of the central nervous system. Scrapie-associated fibrils [and their major protein, prion protein (PrP)] accumulate in the brains of all species affected by scrapie and related diseases. PrP is encoded by a single gene that is linked to (and may be) the major gene controlling the incubation period of the various strains of scrapie pathogens. To investigate the role of PrP in natural scrapie, we have determined its gene structure and expression in the natural host. Sheep are the natural hosts of the pathogens that cause scrapie, an infectious degenerative disorder of the central nervous system. The disease is invariably fatal after incubation periods of several months to years and can persist within a flock by spread between flockmates or by transmission from ewe to lamb (1). The incubation period of the disease depends primarily on the strain(s) of pathogen and the genotype of the affected animal (2). The expense and handling problems of farm animal experiments has meant that much of the work on the host genetic control and transmissibility of scrapie has been done in rodents. The mouse gene Sinc, with two alleles s7 andp7, is the major gene determining the incubation period of all strains of murine scrapie (2-4), and its sheep homologue Sip (with alleles sA and pA) also appears to control the incidence of natural scrapie in at least some breeds of sheep (5). Paradoxically, a candidate product of these host control genes was discovered in studies on the molecular structure of the scrapie pathogen.During the subcellular fractionation of scrapie-affected brain, at least some infectivity copurifies with aggregates of a neuronal membrane protein, the prion protein (PrP) (6). These aggregates were first recognized by electron microscopy and termed scrapie-associated fibrils (7,8

The precursor of the Alzheimer's disease‐specific amyloid A4 protein is an integral, glycosylated membrane protein which spans the bilayer once. The carboxy‐terminal domain of 47 residues was located at the cytoplasmic site of the membrane. The three domains following the transient signal sequence of 17 residues face the opposite side of the membrane. The C‐terminal 100 residues of the precursor comprising the amyloid A4 part and the cytoplasmic domain have a high tendency to aggregate, and proteinase K treatment results in peptides of the size of amyloid A4. This finding suggests that there is a precursor‐product relationship between precursor and amyloid A4 and we conclude that besides proteolytic cleavage other events such as post‐translational modification and membrane injury are primary events that precede the release of the small aggregating amyloid A4 subunit.

The promoter of the gene for the human precursor of Alzheimer's disease A4 amyloid protein (PAD gene) resembles promoters of housekeeping genes. It lacks a typical TATA box and shows a high GC content of 72% in a DNA region that confers promoter activity to a reporter gene in an in vivo assay. Transcription initiates at multiple sites. Sequences homologous to the consensus binding sites of transcription factor AP‐1 and the heat shock control element binding protein were found upstream of the RNA start sites. Six copies of a 9‐bp‐long GC‐rich element are located between positions −200 and −100. A protein–DNA interaction could be mapped to this element. The 3.8 kb of the 5′ region of the PAD gene include two Alu‐type repetitive sequences. These findings suggest that four mechanisms may participate in the regulation of the PAD gene and could be of relevance for the progression of amyloid deposition in Alzheimer's disease.