SLC6A4 and melanoma: Sert-KO mice carry a Sert mutant with targeted deletion of exon 2 that results in expression of nonfunctional SERT protein.67 Before B16-OVA melanoma challenge, these mice exhibited normal numbers of T cells in the periphery (Figure S3A), which displayed a typical naive phenotype (CD25loCD44loCD62Lhi; Figure S3B).