The Belgrade Rat: A Mutation in a Critical Metal Transporter

DESCRIPTION (Adapted from the applicant's abstract): The Belgrade (b/b) rat has a G185R mutation in DMT1, resulting in a hypochromic, microcytic anemia that is inherited as a recessive. DMT1 is a Fe2+/H+ symporter, transporting iron into the duodenum and out of the erythroid endosome. In an expression assay in ooctyes, DMT1 also appears to transport other divalent metals. This proposal is designed to preserve and make available a valuable animal model that is at risk of disappearing just after its mutational basis has been identified. One aim of the proposed research is to understand the role of DMT1 in iron flux and homeostasis and its role in the flux and homeostasis of other metals. The applicants plan to determine metal uptake activity of wild type (185G) and mutant (185R) constructs in a HEK293T cell assay to learn if the mutation affects uptake of each of eight metals (Fe, Mn, Co, Ni, Zn, Cu, Cd and Pb). The applicants will also measure tissue levels of these eight metals in +/+, +/b and b/b rats to see if the levels correlate with mutations in the DMT1 gene itself. A second aim is to learn the role of two isoforms of DMT1 mRNA encoding isoforms of DMT1 that differ in their C-terminal regions. The mutant also provides an opportunity to begin to understand how iron flux and the flux of other metals can continue sufficient for survival of the rat with DMT1 function "knocked out." These aims will also be evaluated relative to systemic iron status, and in other mutants affecting the HFE gene and beta2-microglobulin, a protein complex recently shown to play a regulatory role in iron uptake. The proposed research should have a significant bearing on understanding the basis of iron deficiency, the most prevalent disorder in the world; on iron overload including hereditary hemochromatosis, the most prevalent genetic disease in the US; and on nutrition and toxicity of the other seven metals, of which several, including lead and manganese, have important public health relevance.