The microRNAs Let7c and miR21 are recognized by neuronal toll-like receptor 7 to restrict dendritic growth of neurons.

The microRNAs Let7c and miR21 are recognized by neuronal toll-like receptor 7 to restrict dendritic growth of neurons.
Exp Neurol. 2015 Apr 24;
Authors: Liu HY, Huang CM, Hung YF, Hsueh YP
Abstract
Inflammatory responses are known to play critical roles in the regulation of neurodevelopment and neurodegeneration. Although microglial cells are recognized as professional immune cells in brains, recent evidence suggests that neurons also express important receptors and regulators of innate immunity, including toll-like receptor 7 (TLR7), which is a receptor for single-stranded RNAs (ssRNAs). Here, we report that neuronal TLR7 recognizes endogenous ligands such as the miRNAs Let7c and miR21 and play a negative role in controlling neuronal growth in a cell-autonomous manner. We show here that hippocampal CA1 neurons in Tlr7(-/Y) mice had more complex dendritic arbors compared with those of wild-type littermates at postnatal (P) day 7, but not at P21. This observation strengthens a role of TLR7 in restricting neuronal growth during development. In cultured neurons, transient knockdown of Tlr7 promoted axonal and dendritic growth, supporting the cell-autonomous effect of TLR7 on neuronal growth. We observed perceptible levels of Let7c and miR21 in the exosomes of the neuronal cultures as well as in developing brains. Treatment with Let7c and miR21 restricted dendritic growth of wild-type neurons but not Tlr7(-/-) neurons. Our study suggests...

Source: Experimental Neurology - April 24, 2015 Category: Neurology Authors: Liu HY, Huang CM, Hung YF, Hsueh YP Tags: Exp Neurol Source Type: research