However, re‐expression of engineered GPIbα protein, in which the extracellular domain is replaced by the α‐subunit of human interleukin 4 receptor in GPIbα knockout mice (Gp1ba−/−;TG), reverses the macrothrombocytopenia observed in GPIbα knockout mice but Gp1ba−/−;TG mice still present defective platelet adhesion (Bergmeier et al, 2006). The gene discussed is GP1BA; the disease is Macrothrombocytopenia.