One potential mechanism, coined the metabotropic glutamate receptor (mGluR) theory of FXS, was proposed following observations linking mGluR signaling, long-term depression (LTD), protein synthesis, and FMRP function (Weiler et al., 1997; Huber et al., 2000, 2001, 2002) and has been a focus of recent basic and clinical research (Bear et al., 2004; Dölen et al., 2007; Ronesi and Huber, 2008; Berry-Kravis, 2014). The gene discussed is FMR1; the disease is fragile X syndrome.