IGF1 and Rett syndrome: We also observed reduced numbers of astrocytes (GFAP-positive cells) in the frontal cortex and hippocampus and as well as lower plasma IGF in female Mecp2+/− rats (Fig 7 and Tables 4 and 5), consistent with previous findings of stunted morphological and functional development of astrocytes [36, 37, 71] and reduced IGF signaling [38, 72, 73] in both RTT patients and Mecp2 mutant mice.