Animal Studies Describe Roles of ApoE4 Protein  How the
ApoE4 protein increases the brain’s susceptibility to
Alzheimer’s disease remains unknown. We do know that as the
protein circulates in the blood, it helps to regulate
 cholesterol levels and protect against vascular disease.
ApoE is also produced in the brain, where it is involved in
clearing away beta-amyloid as well as regulating the transport
of cholesterol. Animal studies are also uncovering roles for
ApoE and other proteins in the development and function of
synapses, the tiny structures that connect neurons and enable
them to communicate with each other.  Scientists at Georgetown
University in Washington, DC, and Duke University in Durham, NC,
discovered abnormalities in the synaptic development in mouse
models carrying the APOEε4 allele even before the mice reached
puberty. Their neurons had fewer dendrites, the branch-like
structures that receive messages from other neurons, than those
of APOEε3 or APOEε2 model mice (Dumanis et al., 2009). This