When the four FXS carriers were excluded from the analysis, both mGluR5 density and expression were higher (+17%; t = 1.88, df = 25, P = 0.071 and +25%; t = 1.51, df = 24, P = 0.147, respectively), but only mGluR5 density was marginally significant between FXS patients and control samples. Here, GRM5 is linked to fragile X syndrome.