Update publication information. To identify the downstream substrate/effector that mediates Ptpn21 function. We applied comprehensive phosphoproteomics analysis with Lin- cells isolated from Ptpn21-/- and Ptpn21+/+ mice. The analysis revealed many pTyr sites on molecules associated with cytoskeleton. Additionally, we present a list of Ptpn21-dependent targets and putative substrates including Septin1 with increased tyrosine phosphorylation.