Relationships of APOE genotypes with small RNA and protein cargo of brain tissue extracellular vesicles from patients with late-stage AD

Background and Objectives Variants of the apolipoprotein E (APOE) gene are the greatest known risk factors for sporadic Alzheimer disease (AD). Three major APOE isoform alleles, ϵ2, ϵ3, and ϵ4, encode and produce proteins that differ by only 1-2 amino acids but have different binding partner interactions. Whereas APOE ϵ2 is protective against AD relative to ϵ3, ϵ4 is associated with an increased risk for AD development. However, the role of APOE in gene regulation in AD pathogenesis has remained largely undetermined. Extracellular vesicles (EVs) are lipid bilayer-delimited particles released by cells to dispose of unwanted materials and mediate intercellular communication, and they are implicated in AD pathophysiology. Brain-derived EVs (bdEVs) could act locally in the tissue and reflect cellular changes. To reveal whether APOE genotype affects EV components in AD brains, bdEVs were separated from patients with AD with different APOE genotypes for parallel small RNA and protein profile. Methods bdEVs from late-stage AD brains (BRAAK stages 5-6) from patients with APOE genotypes ϵ2/3 (n = 5), ϵ3/3 (n = 5), ϵ3/4 (n = 6), and ϵ4/4 (n = 6) were separated using our published protocol into a 10,000g pelleted extracellular fraction (10K) and a further purified EV fraction. Counting, sizing, and multiomic characterization by small RNA sequencing and proteomic analysis were performed for 10K, EVs, and source tissue. Results Comparing APOE genotypes, no significant differences in bdEV total particle concentration or morphology were observed. Overall small RNA and protein profiles of 10K, EVs, and source tissue also did not differ substantially between different APOE genotypes. However, several differences in individual RNAs (including miRNAs and tRNAs) and proteins in 10K and EVs were observed when comparing the highest and lowest risk groups (ϵ4/4 and ϵ2/3). Bioinformatic analysis and previous publications indicate a potential regulatory role of these molecules in AD. Discussion For patients with late-stage AD in this study, only a few moderate differences were observed for small RNA and protein profiles between APOE genotypes. Among these, several newly identified 10K and EV-associated molecules may play roles in AD progression. Possibly, larger genotype-related differences exist and are more apparent in or before earlier disease stages

Design for a Millimeter-Scale Walking Robot Design for a Millimeter-Scale Walking Robot

ABSTRACT A design is presented for a millimeter-scale walking robot. The five-millimeter-long robot would be fabricated using micro-lithographic techniques. The design specifies six identical legs, each of which is a discrete microelectromechanical system (MEMS), and for which detailed design drawings already have been developed. Each of the legs incorporates and integrates only motors and drive mechanisms that previously have been fabricated and demonstrated elsewhere, in other types of MEMS devices

Optimal signal-to-noise ratio for silicon nanowire biochemical sensors

The signal-to-noise ratio (SNR) for silicon nanowire field-effect transistors operated in an electrolyte environment is an essential figure-of-merit to characterize and compare the detection limit of such devices when used in an exposed channel configuration as biochemical sensors. We employ low frequency noise measurements to determine the regime for optimal SNR. We find that SNR is not significantly affected by the electrolyte concentration, composition, or pH, leading us to conclude that the major contributions to the SNR come from the intrinsic device quality. The results presented here show that SNR is maximized at the peak transconductance

Temperature dependence of 1∕f noise mechanisms in silicon nanowire biochemical field effect transistors

The 1∕f noise of silicon nanowire biochemical field effect transistors is fully characterized from weak to strong inversion in the temperature range 100–300 K. At 300 K, our devices follow the correlated Δn-Δμ model. As the temperature is lowered, the correlated mobility fluctuations become insignificant and the low frequency noise is best modeled by the Δn-model. For some devices, evidence of random telegraph signals is observed at low temperatures, indicating that fewer traps are active and that the 1∕f noise due to number fluctuations is further resolved to fewer fluctuators, resulting in a Lorentzian spectrum

Regenerative Electronic Biosensors Using Supramolecular Approaches

A supramolecular interface for Si nanowire FETs has been developed with the aim of creating regenerative electronic biosensors. The key to the approach is Si-NWs functionalized with β-cyclodextrin (β-CD), to which receptor moieties can be attached with an orthogonal supramolecular linker. Here we demonstrate full recycling using the strongest biomolecular system known, streptavidin (SAv)–biotin. The bound SAv and the linkers can be selectively removed from the surface through competitive desorption with concentrated β-CD, regenerating the sensor for repeated use. An added advantage of β-CD is the possibility of stereoselective sensors, and we demonstrate here the ability to quantify the enantiomeric composition of chiral targets

Brain tissue-derived extracellular vesicles in Alzheimer's disease display altered key protein levels including cell type-specific markers

Background: Brain tissue-derived extracellular vesicles (bdEVs) play neurodegenerative and protective roles, including in Alzheimer's disease (AD). Extracellular vesicles (EVs) may also leave the brain to betray the state of the CNS in the periphery. Only a few studies have profiled the proteome of bdEVs and source brain tissue. Additionally, studies focusing on bdEV cell type-specific surface markers are rare. Objective: We aimed to reveal the pathological mechanisms inside the brain by profiling the tissue and bdEV proteomes in AD patients. In addition, to indicate targets for capturing and molecular profiling of bdEVs in the periphery, CNS cell-specific markers were profiled on the intact bdEV surface. Methods: bdEVs were separated and followed by EV counting and sizing. Brain tissue and bdEVs from age-matched AD patients and controls were then proteomically profiled. Total tau (t-tau), phosphorylated tau (p-tau), and antioxidant peroxiredoxins (PRDX) 1 and 6 were measured by immunoassay in an independent bdEV separation. Neuron, microglia, astrocyte, and endothelia markers were detected on intact EVs by multiplexed ELISA. Results: Overall, concentration of recovered bdEVs was not affected by AD. Proteome differences between AD and control were more pronounced for bdEVs than for brain tissue. Levels of t-tau, p-tau, PRDX1, and PRDX6 were significantly elevated in AD bdEVs compared with controls. Release of certain cell-specific bdEV markers was increased in AD. Conclusion: Several bdEV proteins are involved in AD mechanisms and may be used for disease monitoring. The identified CNS cell markers may be useful tools for peripheral bdEV capture