Apolipoprotein E | APOE Promoter
Another candidate gene of interest in response and repair
processes following TBI is the gene encoding apolipoprotein E (apoE).
ApoE is a complex glycolipoprotein that facilitates the uptake,
transport, and distribution of lipids. A four-exon gene, APOE, codes
for apoE on chromosome 19 in humans. The gene for apoE has three
major alleles: APOE*E2, APOE*E3, and APOE*E4. These
alleles differ in amino acids at positions 112 and 158: *E2 (cysteine/cysteine), *E3 (cysteine/arginine),
and *E4 (arginine/arginine).
ApoE appears to play an important role in neuronal repair and plasticity
after neurotrauma (Chen et al. 1997). Animal models
suggest a link between the *E4 allele
and increased mortality, extent of damage, and poor repair following
trauma (Chen et al. 1997; Hartman et al. 2002).
The human *E4 allele has been associated with a variety
of disorders with prominent cognitive dysfunction, including normal subjects
with memory complaints (Laws et al. 2002), Alzheimer's disease,
and poor outcomes in stroke and TBI (Chen et al. 1997; Nathoo et al. 2003).