Genetics of Alzheimer's disease

Genetic forms

Less than 1% patients have a disease of purely genetic origin. This form is characterized by:

* There are signs before age 60;
* An autosomal dominant (half of each generation is reached).

Two genes are involved:

* Mutation in the APP gene on chromosome 21 that encodes a precursor of the amyloid protein (five codon 717 mutations are known);
* A PSEN1 mutation on chromosome 14 (many mutations that are false sense mutations).

Genetic Susceptibility

The forms are sporadic, ie non-family, also have a genetic predisposition:

* Is the existence, discovery in 1993 of the apoE4 allele is 4 of the gene Apolipoprotein E that is significantly linked to increased risk of Alzheimer's disease. But the presence of the apoE4 is neither necessary nor sufficient to develop the disease;
* The gene Apolipoprotein E is present in three alleles: the APOE2, APOE3 and apoE4. The first is found in 51% of the population, the second occurs in 80% of the population and the third is found in 15% of the population;
* The presence of the apoE4 in the form heterozygous increases by 2 the risk of Alzheimer's disease;
* The presence of the apoE4 in the form homozygous increases by 11 the risk of Alzheimer's disease.

The apolipoprotein E intervene in neuronal repair mechanisms.