Alzheimer's disease (AD) is the most common form of age-related dementia, characterized by progressive memory loss and cognitive disturbance. Mutations of presenilin 1 (PS1) and presenilin 2 (PS2) are causative factors for autosomal-dominant early-onset familial AD (FAD). Induced pluripotent stem cell (iPSC) technology can be used to model human disorders and provide novel opportunities to study cellular mechanisms and establish therapeutic strategies against various diseases, including neurodegenerative diseases. Here we generate iPSCs from fibroblasts of FAD patients with mutations in PS1 (A246E) and PS2 (N141I), and characterize the differentiation of these cells into neurons. We find that FAD-iPSC-derived differentiated neurons have increased amyloid β42 secretion, recapitulating the molecular pathogenesis of mutant presenilins. Furthermore, secretion of amyloid β42 from these neurons sharply responds to γ-secretase inhibitors and modulators, indicating the potential for identification and validation of candidate drugs. Our findings demonstrate that the FAD-iPSC-derived neuron is a valid model of AD and provides an innovative strategy for the study of age-related neurodegenerative diseases.

BackgroundParkinson’s disease (PD) is a neurodegenerative disease characterized by selective degeneration of dopaminergic neurons in the substantia nigra (SN). The familial form of PD, PARK2, is caused by mutations in the parkin gene. parkin-knockout mouse models show some abnormalities, but they do not fully recapitulate the pathophysiology of human PARK2.ResultsHere, we generated induced pluripotent stem cells (iPSCs) from two PARK2 patients. PARK2 iPSC-derived neurons showed increased oxidative stress and enhanced activity of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. iPSC-derived neurons, but not fibroblasts or iPSCs, exhibited abnormal mitochondrial morphology and impaired mitochondrial homeostasis. Although PARK2 patients rarely exhibit Lewy body (LB) formation with an accumulation of α-synuclein, α-synuclein accumulation was observed in the postmortem brain of one of the donor patients. This accumulation was also seen in the iPSC-derived neurons in the same patient.ConclusionsThus, pathogenic changes in the brain of a PARK2 patient were recapitulated using iPSC technology. These novel findings reveal mechanistic insights into the onset of PARK2 and identify novel targets for drug screening and potential modified therapies for PD.

The expansion of the GGGGCC hexanucleotide repeat in the non-coding region of the Chromosome 9 open-reading frame 72 (C9orf72) gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). This genetic alteration leads to the accumulation of five types of poly-dipeptides translated from the GGGGCC hexanucleotide repeat. Among these, poly-proline-arginine (poly-PR) and poly-glycine-arginine (poly-GR) peptides are known to be neurotoxic. However, the mechanisms of neurotoxicity associated with these poly-dipeptides are not clear. A proteomics approach identified a number of interacting proteins with poly-PR peptide, including mRNA-binding proteins, ribosomal proteins, translation initiation factors and translation elongation factors. Immunostaining of brain sections from patients with C9orf72 ALS showed that poly-GR was colocalized with a mRNA-binding protein, hnRNPA1. In vitro translation assays showed that poly-PR and poly-GR peptides made insoluble complexes with mRNA, restrained the access of translation factors to mRNA, and blocked protein translation. Our results demonstrate that impaired protein translation mediated by poly-PR and poly-GR peptides plays a role in neurotoxicity and reveal that the pathways altered by the poly-dipeptides-mRNA complexes are potential therapeutic targets for treatment of C9orf72 FTD/ALS.

TAR DNA-binding protein-43 (TDP-43) has been recently identified as a major component of the ubiquitinated inclusions found in frontotemporal lobar degeneration with ubiquitinpositive inclusions and in amyotrophic lateral sclerosis, diseases that are collectively termed TDP-43 proteinopathies. Several amyotrophic lateral sclerosis-linked mutations of the TDP-43 gene have also been identified; however, the precise molecular mechanisms underlying the neurodegeneration remain unclear. To investigate the biochemical characteristics of TDP-43, we examined truncation, isoforms, and cytoplasmic inclusion (foci) formation using TDP-43-expressing cells. Under apoptosis, caspase-3 generates two 35-kDa (p35f) and 25-kDa (p25f) fragments. However, in caspase-3(؊/؊) cells, novel caspase-3-independent isoforms of these two variants (p35iso and p25iso) were also detected under normal conditions. With a deletion mutant series, the critical domains for generating both isoforms were determined and applied to in vitro transcription/translation, revealing alternate in-frame translation start sites downstream of the natural initiation codon. Subcellular localization analysis indicated that p35 (p35f and p35iso) expression leads to the formation of stress granules, cellular structures that package mRNA and RNA-binding proteins during cell stress. After applying proteasome inhibitors, aggresomes, which are aggregates of misfolded proteins, were formed in the cytoplasm of cells expressing p35. Collectively, this study demonstrates that the 35-kDa isoforms of TDP-43 assemble in stress granules, suggesting that TDP-43 plays an important role in translation, stability, and metabolism of mRNA. Our findings provide new biological and pathological insight into the development of TDP-43 proteinopathies. Amyotrophic lateral sclerosis (ALS)2 was first reported in 1869 by the French neurologist Jean-Martin Charcot and is one of the most serious neurological diseases. ALS is characterized by progressive degeneration of upper and lower motor neurons, and although the vast majority of ALS cases are sporadic (sALS), almost 10% appear to be familial (fALS). Although mutations in the gene encoding the antioxidant enzyme Cu,Znsuperoxide dismutase-1 (SOD-1) have been detected in 20% of fALS patients (1), the cause of sALS and fALS not associated with SOD-1 remains unclear. Recently, two research groups have identified TDP-43 as a major component of ubiquitinated neuronal cytoplasmic and intranuclear inclusions identified in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U), as well as in sALS (2, 3). Missense mutations in TDP-43 have been found in autosomal dominant ALS families, suggesting that mutant TDP-43 may be a primary cause of motor neuron degeneration (4 -9). Importantly, pathological analysis revealed that abnormal accumulation of TDP-43 does not occur in fALS cases with SOD-1 mutations, suggesting that the pathological process in sALS is distinct from those associated with SOD-1 mutations. Currently, FTLD-U, sALS, ...

Immunoreactive vWF in the endocardial endothelium was increased in overloaded human atrial appendage, which may be a local predisposing factor for intraatrial thrombogenesis.