In the present study, the overexpression of the MECP2 gene was observed in the neuronal-like cells differentiated from the PB-MSCs of mental retardation female carrying FMR1 full mutation allele; nonetheless, MECP2 gene expression showed no difference in the normal female with FMR1 full mutation, compared to that of the female carrying the normal allele. The gene discussed is MECP2; the disease is Intellectual disability.