ApoE C112R (C130R) Screening test for: Alzheimer disease and cardiovascular diseases. The APOE gene is located on chromosome 19 and encodes for the apolipoprotein E (ApoE), a plasma glycoprotein involved in the transport of cholesterol which binds to amyloid protein. ApoE performs the function of lipid carrier; primarily synthesized in the liver, it constitutes the 1-2% of high density lipoprotein (HDL) and plays a critical role in the formation of VLDL (very low density lipoprotein) of chylomicrons. In particular, it mediates the binding, internalization and catabolism of lipoproteins. The APOE gene, located in 19q13.2, encodes a protein of 299 amino acids actively synthesized at the level of hepatocytes. The gene is polymorphic with three common alleles * e2, * e3 and e4 * which produce three protein isoforms E2, E3 and E4.

These isoforms differ in amino acid sequence at positions 112 and 158. Alzheimer’s disease is a degenerative disease of the brain cells that causes dementia, which is a progressive decline of intellectual functions and memory, changes in personality and behavior. It occurs mainly after age 60, although there are much rarer cases of onset between 30 and 50 years. There are sporadic (75%) and familial forms (25%). The e4 allele has been associated with Alzheimer’s disease with late-onset familial and sporadic forms. The disease risk is dose-dependent (presence of only one e4 allele rather than two) as well as the lowering of the age of onset. The presence of heterozygous e4 allele would increase the risk factor of developing the disease (approximately 3 times higher compared to its absence); the presence in homozygosity would result in an even greater risk. Subsequent studies have also explained the reasons for this association: the ApoE e4 allele binds with higher affinity amyloidogenic fibrils causing more precipitation and therefore a faster formation of senile plaques.

The subjects carriers of the E4 protein are also at risk for cardiovascular disease (for increased levels of LDL cholesterol). The e2 allele is more associated to family hyperlipoproteinemia type III, characterized by xanthomas, and high levels of triglycerides and cholesterol. The kit ApoE C112R (C130R) constitutes, together with the kit ApoE R158C (R176C), the genotyping panel for Apoe. Are both available in combinations of 24, 48 and 72 reactions.

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