Intrathecal injection of CSF from AD patients (containing highly expressed let-7b) into the CSF of wild-type mice resulted in neurodegeneration, whereas injection into CSF of mice lacking TLR7 did not result in neurodegeneration, suggesting the pivotal role of microRNAs such as let-7b in TLR7 signaling mediated CNS damage (Lehmann et al., 2012; Figure 3). This evidence concerns the gene TLR7 and Alzheimer disease.