Apolipoprotein E (APOE) is a multifunctional protein that plays significant roles in important cellular mechanisms in peripheral tissues and is as well expressed in the central nervous system, notably by adult neural stem cells (NSCs) in the hippocampus. Evidence from animal studies suggest that APOE is critical for adult NSC maintenance. However, whether APOE has the potential to play a similar role in human NSCs has not been directly investigated. To address this question, we conducted a focused study characterising APOE gene and protein expression in an in vitro model of neural differentiation utilising human induced pluripotent stem cells. We found that APOE gene expression was dramatically decreased as the cells became more differentiated, indicating that APOE expression levels reflect the degree of cellular differentiation during neural induction. Furthermore, qualitative analysis results of immunocytochemistry showed that intracellular localisation of APOE protein becomes more pronounced as neural differentiation progresses. Taken together, our findings suggest a potential role for APOE in human NSC maintenance and justify further investigations being carried out to understand whether changes in APOE levels can directly impact the neurogenic capacity of human stem cells.
Quantitation of apolipoprotein E mRNA in the liver and peripheral tissues of nonhuman primates.
