This proposal consists of three interdependent subprojects designed to study hereditary hemochromatosis (HH), one of the most common inherited diseases in humans. We plan to define the morbidity associated with homozygosity for the HH gene, to determine the factors which regulate iron absorption from the gut and iron recycling from macrophages and, finally, to isolate and characterize the HH gene. Subproject 1 is a population based survey in an area with 1.4 million inhabitants which will determine the frequency of clinical manifestations, iron loading without clinical manifestations and the absence of iron loading in subjects homozygous for the HH gene. We will ascertain two groups of homozygotes, clinically affected individuals and a clinically unselected group (relatives of probands). Vital records, liver biopsy reports from regional hospitals and our own clinic population will be the sources of probands. Accurately determining disease related morbidity and mortality will permit a rational assessment of the cost/benefit ratio of large scale screening programs designed to identify HH homozygotes. Subproject 2 will utilize a unique mouse that lacks transferrin (the hpx mouse) in a series of in vivo experiments designed to define the signal(s) involved in regulating iron absorption and recycling. A complementary series of in vitro experiments will examine factors regulating the release of iron from macrophages. A correlation between the in vivo and in vitro experiments should permit us to characterize the regulatory mechanisms involved in iron metabolism. Regulatory steps that are altered in HH could then be approached. Subproject 3 will utilize material from 103 local pedigrees with HH to isolate and charaterize the HH gene. Polymorphic probes mapping to the HLA class I region of chromosome 6 will be used to create a large scale restriction map of the region using pulsed field gel technology. A disequilibrium analysis will identify polymorphisms associated with HH and 3 recombinant pedigrees will be studied to define the borders of the region containing the HH gene. Finally, single copy sequences mapped to the region will be used to probe Northern blots prepared from gut mucosal cells and macrophages to identify candidate gene products of the HH locus.
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