Binding of MECP2 to the PTPN4 gene promoter stimulates PTPN4 transcription. PTPN4 gene encodes a protein tyrosine phosphatase, non-receptor type, also known as MEG, PTPase-MEG1 or PTPMEG. Expression of Ptpn4 is reduced in Mecp2 null mice used as a Rett syndrome model. A hemizygous PTPN4 gene deletion was found in twins with a Rett-like phenotype (Williamson et al. 2015).