SOX21 and brain inflammatory disease: The radiation-induced upregulation of miR-181b-2-3p and the downregulation of the SOX21 mRNA and protein in NSCs in the present study suggest that the direct interaction of miR-181b-2-3p with SOX 21 may regulate the radiation-induced impairment of neurogenesis not only by directly targeting NSCs but also by indirectly inducing microglial activation, proliferation and subsequent brain inflammation.