PTPN9 and type 2 diabetes mellitus: Diverse PTPs, such as PTPN1, PTPN2, PTPN9, PTPN11, PTPRS, and DUSP9, have been reported to attenuate insulin signaling and trigger type 2 diabetes, indicating that PTPs are promising drug targets for the treatment or prevention of type 2 diabetes [6,7,8].