Overexpression of the major
myelin proteolipid protein (PLP) is detrimental to brain development and function and is the most common cause of
Pelizaeus-Merzbacher disease.
microRNA (
miRNA), small, noncoding RNAs, have been shown to play critical roles in oligodendrocyte lineage. In this study, we sought to investigate whether
miRNAs control PLP abundance. To identify candidate
miRNAs involved in this regulation, we have examined differentiation-induced changes in the expression of
miRNAs in the oligodendroglial cell line Oli-neu and in
enhanced green fluorescent protein positive oligodendrocytes ex vivo. We have identified 145
miRNAs that are expressed in oligodendrocyte cell lineage progression. Dicer1 expression decreases in differentiated oligodendrocytes, and knock down of Dicer1 results in changes in
miRNAs similar to those associated with differentiation. To identify
miRNAs that control the PLP expression, we have selected
miRNAs whose expression is lower in differentiated vs. undifferentiated Oli-neu cells and that have one or more binding site(s) in the PLP 3'-untranslated region (
3'UTR). The PLP
3'UTR fused to the
luciferase gene reduces the activity of the reporter, suggesting that it negatively regulates message stability or translation. Such suppression is relieved by knock down of miR-20a. Overexpression of miR-20a decreases expression of the endogenous PLP in primary oligodendrocytes and of the reporter gene. Deletion or mutation of the putative binding site for miR-20a in the PLP
3'UTR abrogated such effects. Our data indicate that
miRNA expression is regulated by Dicer1 levels in differentiated oligodendrocytes and that miR-20a, a component of the cluster that controls oligodendrocyte cell number, regulates PLP gene expression through its
3'UTR.