Because of the tremendous clinical importance of various SLC22 transporters (OAT1, OAT3, OCT1, OCT2, URAT1, OCTN2) in pharmacology and disease (e.g. hyperuricemia, systemic carnitine deficiency), a great deal of functional analysis of mutations and SNPs already exists (reviewed in [1], S4 Table). The gene discussed is SLC22A2; the disease is systemic primary carnitine deficiency disease.