To account for the variability in duplication size and MECP2 overexpression among MDS patients, we selected two well-characterized human transgenic MDS models developed by the Zoghbi lab (35)—MECP2Tg1 (Tg1), which expresses MECP2 at approximately two-fold the wild-type level, and MECP2Tg3 (Tg3), which expresses MECP2 at approximately three- to five-fold the wild-type level—to evaluate the efficacy of the lead siRNA. This evidence concerns the gene MECP2 and myelodysplastic syndrome.