Small intestinal development requires controls to coordinate morphogenesis and differentiation along spatial and temporal axes. These mechanisms are unknown but are thought to involve homeobox genes. We hypothesize that the spatial and temporal expression patterns of homeobox genes Hoxa-5, Hoxb-4, Hoxb-5, and Hoxb-6 will suggest roles in regulating cell fate during villous/crypt formation. We are testing this by Western blot and immunocytochemistry in Swiss Webster mouse proximal, middle, and distal small intestine, fetal day 13.5 (E13.5) to postnatal day 2 (P2). On Western blot Hoxb-4 protein expression is weak, while Hoxa-5, Hoxb-5, and Hoxb-6 show spatial and temporal changes (Table).
Hoxb-5 immunocytochemistry is complete and shows expression 1) in a circumferential band of submucosal cells during early villous formation which disappears then reappears during early crypt formation; and 2) in clusters of serosal layer cells which change spatially and temporally and localize under villous/crypt structures. We conclude that Hoxa-5, Hoxb-5, and Hoxb-6 exhibit spatial and temporal regulation in developing small intestine which suggests roles in cell phenotype commitment during early villous/crypt formation.(Supported by DK39428 and DK07471)
