MECP2 and Rett syndrome: Mecp2+/− Jae (Mecp2tm1.1Jae) heterozygous female mice, carrying a deletion on exon 3 in Mecp2, mimic a milder RETT phenotype that well recapitulates the somatic mosaicism of Mecp2 mutation reported in RTT patients and develop later RTT patient symptoms including irregular breathing, abnormal gait, and hind limb clasping [48].