Developmental, regional, and cellular expression of SFT/UbcH5A and DMT1 mRNA in brain

Brain iron has marked developmental, regional, and cellular distribution patterns. To characterize better the potential mechanisms for iron transport into and within the brain, we have analyzed expression patterns of two factors: divalent metal transporter 1 (DMT1) and stimulator of Fe transport (SFT). DMT1 is known to participate in brain iron uptake although functional information is lacking. Even less clear is the possible role of SFT, which is related to a member of the ubiquitin-conjugating E2 family UbcH5A, but previous studies have found SFT/Ubc5Ha mRNA expressed abundantly in mouse brain. Like DMT1, SFT function has been implicated in transferrin and nontransferrin-bound iron uptake. Comparative Northern analysis indicates that SFT/UbcH5A mRNA levels are threefold higher in 3-day-old mice than at later ages, whereas levels of DMT1 mRNA do not change. In situ analysis of neonatal mouse brain reveals prominent SFT/UbcH5A mRNA expression in epithelial and ependymal cells in the choroid plexus and neurons of the olfactory bulb, hippocampus, and cortex. Adult mouse brain expresses SFT/UbcH5A mRNA mainly in white matter of the cerebellum and pons. Using a multiple tissue expression (MTE) array containing 20 different human brain regions, the highest levels of both SFT/UbcH5A and DMT1 mRNA are detected in the corpus callosum and cerebellum. The significantly elevated levels of SFT/UbcH5A mRNA in the neonatal mouse and its localization to choroid plexus, a major site of brain iron acquisition, suggest that this factor may contribute to the rapid rate of brain iron uptake that occurs in the early postnatal period.