PubMed · 12877023
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Kazuhiko Saito. 2003. [Obsessional idea, obsessional rumination].. https://pubmed.ncbi.nlm.nih.gov/12877023/
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Alzheimer's disease (AD) is characterized by the presence of toxic protein aggregates or plaques composed of the amyloid β (Aβ) peptide. Various lengths of Aβ peptide are generated by proteolytic cleavages of the amyloid precursor protein (APP). Mutations in many familial AD-associated genes affect the production of the longer Aβ42 variant that preferentially accumulates in plaques. In the case of sporadic or late-onset AD, which accounts for greater than 95% of cases, several genes are implicated in increasing the risk, but whether they also cause the disease by altering amyloid levels is currently unknown. Through loss of function studies in a model cell line, here RNAi-mediated silencing of several late onset AD genes affected Aβ levels is shown. However, unlike the genes underlying familial AD, late onset AD-susceptibility genes do not specifically alter the Aβ42/40 ratios and suggest that these genes probably contribute to AD through distinct mechanisms.
BACKGROUND: The order and magnitude of pathologic processes in Alzheimer's disease are not well understood, partly because the disease develops over many years. Autosomal dominant Alzheimer's disease has a predictable age at onset and provides an opportunity to determine the sequence and magnitude of pathologic changes that culminate in symptomatic disease. METHODS: In this prospective, longitudinal study, we analyzed data from 128 participants who underwent baseline clinical and cognitive assessments, brain imaging, and cerebrospinal fluid (CSF) and blood tests. We used the participant's age at baseline assessment and the parent's age at the onset of symptoms of Alzheimer's disease to calculate the estimated years from expected symptom onset (age of the participant minus parent's age at symptom onset). We conducted cross-sectional analyses of baseline data in relation to estimated years from expected symptom onset in order to determine the relative order and magnitude of pathophysiological changes. RESULTS: Concentrations of amyloid-beta (Aβ)(42) in the CSF appeared to decline 25 years before expected symptom onset. Aβ deposition, as measured by positron-emission tomography with the use of Pittsburgh compound B, was detected 15 years before expected symptom onset. Increased concentrations of tau protein in the CSF and an increase in brain atrophy were detected 15 years before expected symptom onset. Cerebral hypometabolism and impaired episodic memory were observed 10 years before expected symptom onset. Global cognitive impairment, as measured by the Mini-Mental State Examination and the Clinical Dementia Rating scale, was detected 5 years before expected symptom onset, and patients met diagnostic criteria for dementia at an average of 3 years after expected symptom onset. CONCLUSIONS: We found that autosomal dominant Alzheimer's disease was associated with a series of pathophysiological changes over decades in CSF biochemical markers of Alzheimer's disease, brain amyloid deposition, and brain metabolism as well as progressive cognitive impairment. Our results require confirmation with the use of longitudinal data and may not apply to patients with sporadic Alzheimer's disease. (Funded by the National Institute on Aging and others; DIAN ClinicalTrials.gov number, NCT00869817.).
Mutations in CDH1, encoding E-cadherin, are the underlying genetic defect in approximately one-third of the hereditary diffuse gastric cancer (HDGC) families described so far. Tumours arising in these families show abnormal or absence of E-cadherin expression, following the model of tumour suppressor gene inactivation. A single study has been reported showing inactivation of the CDH1 wild-type allele in tumour cells from HDGC families either by promoter methylation or by somatic mutation. In order to find the genetic alteration responsible for the presence of diffuse gastric cancers in four members of a Caucasian family, we have screened the coding sequence of CDH1 for germline mutations and searched for the second inactivating hit in the tumour samples. In this family, we have found a germline splice-site mutation in all members affected by gastric cancer and, in one tumour, a somatic deletion affecting at least exon 8 of CDH1. Our results show that a CDH1 intragenic deletion is the second hit inactivating the wild-type allele, in one of the tumours in this family.