SLC6A4 and Venous thrombosis: More recently, an in vivo venous thrombosis model demonstrated that the extent of thrombus formation depends on the serotonin transporter (SERT) rather than on platelet serotonin content: mice lacking SERT formed markedly fewer and smaller thrombi, whereas absence of platelet serotonin (Tph1-/- or SSRI-treated) did not reduce thrombus burden; neutrophil recruitment was also attenuated in SERT-deficient mice.