ATRX and alpha thalassemia spectrum: Localization of Alpha Thalassemia/Mental Retardation Syndrome X-Linked (ATRX) to heterochromatic foci has recently been demonstrated to be a cell-autonomous marker of disease progression in other RTT mouse models (Baker et al., 2013), so we evaluated ATRX localization using IF on comparable sections of the CA1, CA2, and CA3 regions of the hippocampus from 7-week-old mice (Figure 4D).