Future studies should also examine: (i) GUS expression at both mRNA and protein levels in adults with FXSD including FXS, to rule out any associations with FMRP deficit; and (ii) to compare SDHA and EIF4A2 normalization strategy as well as the ratio between the two internal controls across FXSD including FXS. The gene discussed is FMR1; the disease is fragile X syndrome.