It was then shown that both miR-146a and miR-146b could downregulate IRAK1 expression in vitro (Nahid et al., 2009) and it was proposed that in Rett syndrome the downregulation of miR-146a/b contributes to the overexpression of IRAK1 (Urdinguio et al., 2010). The gene discussed is IRAK1; the disease is Rett syndrome.