The most promising discovery in the study of Alzheimer's disease (AD)
markers is undoubtedly the implication of apolipoprotein E (apoE). The
gene of this apoliprotein is located on chromosome 19 and is characte
rized by three common alleles is an element of 2, is an element of 3 a
nd is an element of 4 giving raise to 6 genotypes and 6 protein phenot
ypes. ApoE is well known for its role in cholesterol transport, Differ
ent studies have been performed, giving major arguments in favor of an
important role of apoE in the pathophysiology of AD, These include th
e discovery of the relationship between the is an element of 4 allele
and AD, the ability of this protein to form complexes with beta amyloi
d protein (A beta) in seniles plates, its presence in neurofibrillary
tangles and in vessels of AD patients, Another important finding is th
e differential interaction between the different isoforms of apoE and
tan protein, Some of the hypotheses implicate the role of different ap
oE isoforms on the growth and extension of neurones, perhaps by a rece
ptor mediated pathway. It has been suggested that apoE acts as a patho
logical chaperone protein, or alternatively that it protects neurons b
y regulation of the cell membrane and modifying calcium homeostasis. I
t is clear that apoE genotype determination alone cannot be used for d
iagnosis of AD. The presence of is an element of 4 allele is only one
of several risk factors for the development of the disease, Other fact
ors may also be implicated and are the subject of ongoing research.