High-affinity transporter for the intake of thiamine (PubMed:11481326, PubMed:11592824, PubMed:12393806, PubMed:22194418, PubMed:12031504). Essential for spermatogenesis (PubMed:14567973, PubMed:14738878). H(+)(in) + thiamine(out) = H(+)(out) + thiamine(in) H(+)(in) + thiamine(out) = H(+)(out) + thiamine(in) H(+)(in) + thiamine(out) = H(+)(out) + thiamine(in) Expressed in cochlear hair cells and duodenum (at protein level) (PubMed:11592824). Detected in pancreatic acinar cells (at protein level) (PubMed:22194418). Also expressed strongly in pancreatic islet cells (PubMed:22194418). Expressed in the testis (PubMed:14738878). Very highly expressed in liver, and also detected at lower levels in heart, testis, kidney, brain and spleen. Expressed at low levels in liver and spleen. At embryonic stage 16.5 dpc detected in intestinal enterocytes, pancreatic acinar cells, and cochlear hair cells (at protein level). In newborn mice, detected in brain, kidney, liver and intestine (at protein level). Induced in a TP53/p53-dependent manner upon DNA damage. Males are infertile with reduced testis size and aspermia (PubMed:14567973, PubMed:14738878). Spermatogenesis fails at the pachytene spermatid stage with apoptosis of germ cells (PubMed:14567973, PubMed:14738878). When fed on a thiamine-free diet, animals develop additional phenotypes including diabetes mellitus, profound hearing loss, and defective hematopoiesis (PubMed:12393806, PubMed:14567973, PubMed:16642288). Pancreatic morphology appears to be normal although insulin secretion is significantly impaired (PubMed:12393806). Erythroid precursors in the bone marrow are almost completely absent leading to loss of reticulocytes in the peripheral blood (PubMed:14567973). The hearing loss phenotype is specifically associated with loss of cochlear inner hair cells (PubMed:16642288). These phenotypes can be reversed in many cases by re-introduction of a high thiamine diet (PubMed:12393806, PubMed:14567973, PubMed:16642288). Thiamine uptake by pancreatic acinar cells from knockout mice was found to be significantly lower than uptake by pancreatic acinar cells of the wild-type littermates (PubMed:22194418). Belongs to the reduced folate carrier (RFC) transporter (TC 2.A.48) family.