Mutation identified as a possible cause of Alzheimer's disease

Article Abstract:

One of the key features of Alzheimer's disease is the senile plaque, which consists of degenerating nerve endings surrounding a core of amyloid, a protein-polysaccharide complex with starch-like characteristics. Amyloid is associated with certain disease states, and in patients with Alzheimer's disease, it is detected in the brain tissues. This amyloid, which gets its name from its amorphous appearance and its staining properties, is chemically different from the amyloid found in systemic amyloid diseases. A major, unresolved problem with Alzheimer's disease is whether amyloid deposition is the cause of the condition or one of the results of the disease process. There now is evidence that, for at least some cases of familiar Alzheimer's disease, a mutation in the amyloid precursor protein may be the fundamental defect that causes the disorder. Researchers began an investigation of the gene for amyloid precursor protein (APP) in members of a family with familial Alzheimer's disease. This particular family was chosen because mapping studies had already shown that in this group the Alzheimer's gene was located on chromosome 21, the same chromosome where the APP gene is found. Molecular biological studies revealed that among the Alzheimer's patients in this family, amino acid 717 in the 770 amino acid APP chain was altered. This particular change is a conservative change. That is, the chemical similarity of the two types of amino acids is great enough that the substitution might be expected to have only minimal impact. The exciting aspect of the finding, however, is that the substitution was found in all the patients, but not in the unaffected members of the family. This mutation cannot account for all cases of Alzheimer's disease, and some other familial Alzheimer's kinships have a gene that maps outside of chromosome 21. Furthermore, the genetic alteration was not found in patients with the sporadic form of Alzheimer's disease, which tends to occur later in life than the familial form. However, the demonstration of the genetic mutation in this family may provide insights into the origin of the disease that may prove useful in understanding even those cases of Alzheimer's disease that arise from different causes. (Consumer Summary produced by Reliance Medical Information, Inc.)

Dementia, Familial diseases

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Dissecting how presenilins function - and malfunction

Article Abstract:

Researchers have discovered that mutations in two genes that produce the two presenilin proteins are present in about half of all patients with inherited Alzheimer's disease. The discovery could aid in finding the cause of nonhereditary Alzheimer's.

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Familial Alzheimer's linked to chromosome 14 gene

Article Abstract:

Human Genome Project research indicates that a genetic defect on chromosome 14 causes an inherited form of Alzheimer's disease that occurs at an unusually early age. Genetic research suggest that at least three other genes can cause Alzheimer's.

Human Genome Project, Chromosome mapping

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