Targeted disruption of the hepatic transferrin receptor 2 gene in mice leads to iron overload.
OBJECTIVE
Transferrin receptor 2 (TfR2) plays a key role in the regulation of iron metabolism. Mutations of TfR2 in humans cause type 3 hereditary hemochromatosis. Although highly expressed in liver, several studies have reported TfR2 expression in other tissues. To determine the contribution of liver expressed TfR2 in iron homeostasis, we have generated and characterized a liver-specific TfR2-knockout (KO) mouse.


METHODS
Liver-specific TfR2-KO mice were generated by crossing TfR2-floxed mice with transgenic albumin-Cre mice. Tissue and serum from homozygous TfR2-floxed mice with and without albumin-Cre were analyzed. Serum transferrin saturation, hepatic, and splenic iron concentrations were determined. The expression of iron-related mRNA transcripts was analyzed by real-time PCR. Levels of the iron-related proteins TfR1, TfR2, ferritin, and prohepcidin were analyzed by immunoblotting.


RESULTS
Liver-specific TfR2-KO mice develop significant iron overload comparable to complete TfR2-KO mice. At all ages studied, transferrin saturation, hepatic iron concentration, and hepatic ferritin were significantly elevated. Hepatic TfR2 mRNA and protein were absent in the livers of liver-specific TfR2-KO mice, and TfR1 expression was reduced consistent with liver iron loading. At 5 weeks of age, hepcidin1 mRNA, and prohepcidin protein were decreased in liver-specific TfR2-KO compared to control mice.


CONCLUSIONS
The significant iron loading and modulation of expression of iron-related genes in liver-specific TfR2-KO mice demonstrates that the liver is the primary site for TfR2 expression and activity and that liver-expressed TfR2 is required for the regulation of hepcidin1.
Wallace
Daniel F
DF
Membrane Transport Laboratory, Cancer and Cell Biology Division, The Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Queensland 4029, Australia.
Summerville
Lesa
L
Subramaniam
V Nathan
VN
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D004386:Duodenum / Q000502:physiology; D005293:Ferritins / Q000097:blood; D017353:Gene Deletion; D064451:Hepcidins; D006706:Homeostasis / Q000502:physiology; D007501:Iron / Q000097:blood; D019190:Iron Overload / Q000473:pathology / Q000503:physiopathology*; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000378:metabolism; D011990:Receptors, Transferrin / Q000235:genetics* / Q000378:metabolism*
D023181:Antimicrobial Cationic Peptides; D064451:Hepcidins; D012333:RNA, Messenger; D011990:Receptors, Transferrin; C503641:TFR2 protein, mouse; D005293:Ferritins; D007501:Iron