Explore the vast range of titles available.

Induced pluripotent stem cells are shown to be useful for studying phenotypes relevant to familial and sporadic Alzheimer’s disease, even though it can take decades for the disease to manifest in patients. Alzheimer's disease in a dish Induced pluripotent stem (iPS) cell cultures are being used as models for various genetic diseases, including Parkinson's disease and diabetes. Alzheimer's disease seems an unlikely candidate for such a technique, because it can take decades for the disease to manifest in patients. But here, Lawrence Goldstein and colleagues provide evidence that iPS cell technology can be used to study phenotypes that are relevant to familial and sporadic Alzheimer's disease. Patient-derived fibroblasts were reprogrammed as iPS cells and differentiated into neurons expressing various biochemical markers of Alzheimer's disease, including elevated amyloid-β secretion. Treatment of neurons with a γ-secretase inhibitor, a type of drug considered a candidate for Alzheimer's therapy, significantly reduced both amyloid-β and phospho-tau levels. Our understanding of Alzheimer’s disease pathogenesis is currently limited by difficulties in obtaining live neurons from patients and the inability to model the sporadic form of the disease. It may be possible to overcome these challenges by reprogramming primary cells from patients into induced pluripotent stem cells (iPSCs). Here we reprogrammed primary fibroblasts from two patients with familial Alzheimer’s disease, both caused by a duplication of the amyloid-β precursor protein gene 1 ( APP ; termed APP Dp ), two with sporadic Alzheimer’s disease (termed sAD1, sAD2) and two non-demented control individuals into iPSC lines. Neurons from differentiated cultures were purified with fluorescence-activated cell sorting and characterized. Purified cultures contained more than 90% neurons, clustered with fetal brain messenger RNA samples by microarray criteria, and could form functional synaptic contacts. Virtually all cells exhibited normal electrophysiological activity. Relative to controls, iPSC-derived, purified neurons from the two APP Dp patients and patient sAD2 exhibited significantly higher levels of the pathological markers amyloid-β(1–40), phospho-tau(Thr 231) and active glycogen synthase kinase-3β (aGSK-3β). Neurons from APP Dp and sAD2 patients also accumulated large RAB5-positive early endosomes compared to controls. Treatment of purified neurons with β-secretase inhibitors, but not γ-secretase inhibitors, caused significant reductions in phospho-Tau(Thr 231) and aGSK-3β levels. These results suggest a direct relationship between APP proteolytic processing, but not amyloid-β, in GSK-3β activation and tau phosphorylation in human neurons. Additionally, we observed that neurons with the genome of one sAD patient exhibited the phenotypes seen in familial Alzheimer’s disease samples. More generally, we demonstrate that iPSC technology can be used to observe phenotypes relevant to Alzheimer’s disease, even though it can take decades for overt disease to manifest in patients.

Defined transcription factors can induce epigenetic reprogramming of adult mammalian cells into induced pluripotent stem cells. Although DNA factors are integrated during some reprogramming methods, it is unknown whether the genome remains unchanged at the single nucleotide level. Here we show that 22 human induced pluripotent stem (hiPS) cell lines reprogrammed using five different methods each contained an average of five protein-coding point mutations in the regions sampled (an estimated six protein-coding point mutations per exome). The majority of these mutations were non-synonymous, nonsense or splice variants, and were enriched in genes mutated or having causative effects in cancers. At least half of these reprogramming-associated mutations pre-existed in fibroblast progenitors at low frequencies, whereas the rest occurred during or after reprogramming. Thus, hiPS cells acquire genetic modifications in addition to epigenetic modifications. Extensive genetic screening should become a standard procedure to ensure hiPS cell safety before clinical use. Genetic abnormalities in iPS cells Epigenomic reprogramming of somatic cells to produce iPS (induced pluripotent stem) cells has important therapeutic potential and is the basis of potentially important disease models. Recent reports that the reprogramming and in vitro culture of iPS cells can induce genetic and epigenetic abnormalities raise concerns over the implications of these abnormalities for clinical applications of iPS cells. Three papers in this issue present genomics studies of human iPS and embryonic stem (ES) cells, and taken together, the results confirm that chromosomal, subchromosomal and single-base level anomalies do accumulate in iPS cells. Hussein et al . compare copy number alterations of early and intermediate passage human iPS cells and report a higher level of copy number variations associated with reprogramming. During moderate length culture, however, iPS cells undergo a selection process leading to a decreased mutation load equivalent to that seen in ES cells. Gore et al . report protein-coding point mutations in 22 human iPS cell lines reprogrammed using five different methods; some mutations were pre-existing in the somatic cells, others were new mutations linked to reprogramming. Lister et al . used whole-genome DNA methylation profiling of human ES, iPS and somatic progenitor cell lines to reveal 'hotspots' in the genomes of iPS cells that are aberrantly reprogrammed. Reprogramming of somatic cells to induced pluripotent stem (iPS) cells that can be differentiated into many cell types has great potential for personalized therapy. This study finds that 22 human iPS cell lines that were reprogrammed using five different methods contain protein coding point mutations. Some mutations were pre existing in the somatic cells, others were new mutations that occurred during and after reprogramming. Therefore, it will be important to ensure iPS cell safety before clinical use.

The extracellular matrix (ECM) plays important roles in influencing cellular behavior such as attachment, differentiation, and proliferation. However, in conventional culture and tissue engineering strategies, single proteins are frequently utilized, which do not mimic the complex extracellular microenvironment seen in vivo. In this study we report a method to decellularize brain tissue using detergents. This decellularized brain matrix is rich in glycosaminoglycans and contains collagen I, collagen III, collagen IV, collagen V, collagen VI, perlecan, and laminin. By further processing the material into a liquid form, the brain matrix can be used as a cell culture coating. Neurons derived from human induced pluripotent stem cells plated on the brain matrix express neuronal markers and assume neuronal morphology. Additionally, the same material can potentially be used as a scaffold for tissue engineering as it reassembles upon injection in vivo to form a gel. Thus, our work demonstrates the ability to use decellularized brain ECM for cell culture and tissue engineering applications.

We identified axonal defects in mouse models of Alzheimer's disease that preceded known disease-related pathology by more than a year; we observed similar axonal defects in the early stages of Alzheimer's disease in humans. Axonal defects consisted of swellings that accumulated abnormal amounts of microtubule-associated and molecular motor proteins, organelles, and vesicles. Impairing axonal transport by reducing the dosage of a kinesin molecular motor protein enhanced the frequency of axonal defects and increased amyloid-{szligbeta} peptide levels and amyloid deposition. Reductions in microtubule-dependent transport may stimulate proteolytic processing of {szligbeta}-amyloid precursor protein, resulting in the development of senile plaques and Alzheimer's disease.

Dominant mutations in ubiquitously expressed superoxide dismutase (SOD1) cause familial ALS by provoking premature death of adult motor neurons. To test whether mutant damage to cell types beyond motor neurons is required for the onset of motor neuron disease, we generated chimeric mice in which all motor neurons and oligodendrocytes expressed mutant SOD1 at a level sufficient to cause fatal, early-onset motor neuron disease when expressed ubiquitously, but did so in a cellular environment containing variable numbers of non-mutant, non-motor neurons. Despite high-level mutant expression within 100% of motor neurons and oligodendrocytes, in most of these chimeras, the presence of WT non-motor neurons substantially delayed onset of motor neuron degeneration, increasing disease-free life by 50%. Disease onset is therefore non-cell autonomous, and mutant SOD1 damage within cell types other than motor neurons and oligodendrocytes is a central contributor to initiation of motor neuron degeneration.

A major goal of stem-cell research is to identify conditions that reliably regulate their differentiation into specific cell types. This goal is particularly important for human stem cells if they are to be used for in vivo transplantation or as a platform for drug development. Here we describe the establishment of procedures to direct the differentiation of human embryonic stem cells and human induced pluripotent stem cells into forebrain neurons that are capable of forming synaptic connections. In addition, HEK293T cells expressing Neuroligin (NLGN) 3 and NLGN4, but not those containing autism-associated mutations, are able to induce presynaptic differentiation in human induced pluripotent stem cell-derived neurons. We show that a mutant NLGN4 containing an in-frame deletion is unable to localize correctly to the cell surface when overexpressed and fails to enhance synapse formation in human induced pluripotent stem cell-derived neurons. These findings establish human pluripotent stem cell-derived neurons as a viable model for the study of synaptic differentiation and function under normal and disorder-associated conditions.

Background Early‐onset Alzheimer’s disease (EOAD) is a complex disease that occurs at an early age at onset (AAO) before 65 years, constituting 5‐6% of all AD cases and remains poorly understood. Patient‐derived induced pluripotent stem cells (iPSCs) have been used to model different forms of EOAD that display heterogeneous disease mechanisms. Method We examined iPSC‐derived neurons from both familial EOAD harboring mutations in PSEN1A79V , PSEN2N141I, and APPV717I and non‐familial EOAD patients at an early AAO. RNA‐seq for familial and non‐familial EOAD patients as well as ATAC‐seq for familial EOAD patients were carried out to characterize the gene expression and chromatin accessibility changes, respectively. Differential expression and enrichment analysis, TF activity identification, and co‐expression module detection were performed for familial EOAD RNA‐seq. Clustering and surrogate neuron marker classification were performed for non‐familial EOAD RNA‐seq. Differential peak analysis, TF motif footprinting and peak functional enrichment were performed for familial EOAD ATAC‐seq. Result Our approach allowed us to identify the correlation between gene expression and chromatin accessibility associated with key disease familial EOAD endotypes. We identified limitations with our non‐familial EOAD neuron model to study sporadic AD, providing evidence that these neurons present variation of differentiation across patient clones, patient variability and an immature culture state. Common endotypes were identified across three familial EOAD mutations such as dedifferentiation of a mature neuron to a less differentiated quasi‐neuron state and repression of mitochondrial function and metabolism. Integrative analysis allowed us to ascertain the master transcriptional regulators associated with these endotypes, including REST, ASCL1, and ZIC family members (activation), as well as NRF1 (repression). Our non‐familial EOAD study showed a modest difference in expression profiling and a limited number of differentially expressed genes (DEGs) between diseased and control subjects. Conclusion iPSC‐derived neurons demonstrated that familial EOAD mutations share common regulatory changes within endotypes with varying severity, leading to reversion to a less‐differentiated neuron state. Extending the usage of these neurons to non‐familial EOAD may not serve as ideal to study sporadic AD. Overall, we have demonstrated that human neuron modeling can be applied to different forms of EOAD to understand the disease etiology better.

Neurons are specialized cells with a complex architecture that includes elaborate dendritic branches and a long, narrow axon that extends from the cell body to the synaptic terminal. The organized transport of essential biological materials throughout the neuron is required to support its growth, function, and viability. In this review, we focus on insights that have emerged from the genetic analysis of long-distance axonal transport between the cell body and the synaptic terminal. We also discuss recent genetic evidence that supports the hypothesis that disruptions in axonal transport may cause or dramatically contribute to neurodegenerative diseases.

The global epidemic of Alzheimer disease (AD) is worsening, and no approved treatment can revert or arrest progression of this disease. AD pathology is characterized by the accumulation of amyloid-β (Aβ) plaques and tau neurofibrillary tangles in the brain. Genetic data, as well as autopsy and neuroimaging studies in patients with AD, indicate that Aβ plaque deposition precedes cortical tau pathology. Because Aβ accumulation has been considered the initial insult that drives both the accumulation of tau pathology and tau-mediated neurodegeneration in AD, the development of AD therapeutics has focused mostly on removing Aβ from the brain. However, striking preclinical evidence from AD mouse models and patient-derived human induced pluripotent stem cell models indicates that tau pathology can progress independently of Aβ accumulation and arises downstream of genetic risk factors for AD and aberrant metabolic pathways. This Review outlines novel insights from preclinical research that implicate apolipoprotein E, the endocytic system, cholesterol metabolism and microglial activation as Aβ-independent regulators of tau pathology. These factors are discussed in the context of emerging findings from clinical pathology, functional neuroimaging and other approaches in humans. Finally, we discuss the implications of these new insights for current Aβ-targeted strategies and highlight the emergence of novel therapeutic strategies that target processes upstream of both Aβ and tau.

Kinesin is an ATP-driven molecular motor protein that moves processively along microtubules. Despite considerable research, the detailed mechanism of kinesin motion remains elusive. We applied an enhanced suite of single- and multiple-molecule fluorescence polarization microscopy assays to report the orientation and mobility of kinesin molecules bound to microtubules as a function of nucleotide state. In the presence of analogs of ATP, ADP-Pi or in the absence of nucleotide, the kinesin head maintains a rigid orientation. In the presence of ADP, the motor domain of kinesin, still bound to the microtubule, adopts a previously undescribed, highly mobile state. This state may be general to the chemomechanical cycle of motor proteins; in the case of kinesin, the transition from a highly mobile to a rigid state after ADP release may contribute to the generation of the 8 nm step.