PTPN11 and colitis: Similar to the observations in human IBD, immunofluorescence staining and Western blotting also revealed the decrease of Gab1 protein in DSS-induced colitis mouse model, while the expression of Gab2 and Gab1-binding protein Src homology region 2–containing protein tyrosine phosphatase 2 (Shp2) was unaltered (Figure 2, A and B).