TREM2 and X-linked retinal dysplasia: Using miRNA array-based analytical approaches, recent findings further indicate that miRNA-9, miRNA-34a, miRNA-125b, miRNA-146a, and miRNA-155 exhibit similar up-regulation in sporadic AD and in PrD brain (Table 1), that miRNA-34a induces a deficiency in the expression of MG cell TREM2, and a defect in the ability of MG cells to phagocytose (Figure 1; Zhao and Lukiw, 2015; Bhattacharjee et al., 2016).