PSEN2

At least 11 mutations in the PSEN2 gene have been shown to cause early-onset Alzheimer's disease. Mutations in this gene account for less than 5 percent of all early-onset cases of the disorder.

Two of the most common PSEN2 mutations that cause early-onset Alzheimer's disease change single protein building blocks (amino acids) used to make presenilin 2. One mutation replaces the amino acid asparagine with the amino acid isoleucine at position 141 (written as Asn141Ile or N141I). The other mutation changes the amino acid methionine to the amino acid valine at position 239 (written as Met239Val or M239V). These mutations appear to disrupt the processing of amyloid precursor protein, leading to the overproduction of amyloid beta peptide. This protein fragment can build up in the brain and form clumps called amyloid plaques that are characteristic of Alzheimer's disease. A buildup of toxic amyloid beta peptide and amyloid plaques may lead to the death of neurons and the progressive signs and symptoms of this disorder.

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