MECP2 and Rett syndrome: Over 300 mutations including missense, nonsense, frame shift, splice site, start codon mutations and deletions are located throughout the MECP2 gene and have been associated with Rett syndrome with different degrees of severity (Chahrour and Zoghbi, 2007; Shah and Bird, 2017; Sheikh et al., 2017; Martinez de Paz et al., 2019; Spiga et al., 2019; Good et al., 2021).