Expression of iron absorption genes in mouse large intestine.
OBJECTIVE
The large intestine has been reported to have a capacity for iron absorption and expresses genes for iron absorption normally found in the duodenum. The importance and function of these genes in the large intestine are not understood. We therefore investigated the cellular localization and regulation of expression of these genes in mouse caecum and colon.


METHODS
Gene expression was measured by real-time PCR using RNA extracted from iron-deficient and hypoxic mouse large intestine, compared to controls. Protein localization and regulation were measured by immunohistochemistry using frozen sections of the large intestine from the same mice.


RESULTS
Dcytb (duodenal ferric reductase) was expressed at very low levels in the large intestine, compared to the duodenum, while Ireg1 and DMT1 were expressed at significant levels in the large intestine and were increased in iron-deficient caecum, proximal and distal colon, with the most significant increases seen in the distal colon. Hypoxia increased Ireg1 expression in the proximal colon. Immunohistochemistry detected significant levels of only IREG1, which was localized to the basolateral membrane of colonic epithelial cells.


CONCLUSIONS
Iron absorption genes were expressed at lower levels in mouse caecum and colon than in the duodenum. They are regulated by body iron requirements. Colonic epithelial cells express basolateral IREG1in the same fashion as in the duodenum and this protein could regulate colonic epithelial cell iron levels.
Takeuchi
Ken
K
Division of Internal Medicine, Diabetes and Endocrinology, King's College, London SE5 9PJ, UK. ken.takeuchi@kcl.ac.uk
Bjarnason
Ingvar
I
Laftah
Abas H
AH
Latunde-Dada
Gladys O
GO
Simpson
Robert J
RJ
McKie
Andrew T
AT
D000818:Animals; D027682:Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D038181:FMN Reductase / Q000096:biosynthesis / Q000235:genetics*; D015870:Gene Expression; D005786:Gene Expression Regulation; D007408:Intestinal Absorption / Q000235:genetics*; D007413:Intestinal Mucosa; D007420:Intestine, Large; D007501:Iron / Q000378:metabolism; D019189:Iron Metabolism Disorders / Q000235:genetics*; D033862:Iron-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D051379:Mice; D023421:Models, Animal; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2
D027682:Cation Transport Proteins; D038181:FMN Reductase; D007501:Iron; D033862:Iron-Binding Proteins; D000098742:Ferroportin; D000099236:Solute Carrier Family 11, Member 2; C023903:ferric citrate iron reductase