Reduced size of the soma and of the nucleus has been pointed out as a typical feature of iPSC-neurons from MECP2-caused Rett syndrome patients [26] and is an important in vitro biomarker of Mecp2 mutation in the mouse also, where it is rescued by IGF-1 (Insulin Growth Factor 1) treatment [30]. This evidence concerns the gene IGF1 and atypical Rett syndrome.