Both the FX clone and its isogenic control stained positive for the pluripotent markers OCT4, SSEA4, and TRA-1-60, but only the FX clone inactivated FMR1 expression following neuronal differentiation (Figure 1B,C), mimicking the natural FMR1 silencing characterizing FXS fetuses at early development. Here, FMR1 is linked to fragile X syndrome.