Tribbles related protein 3 (TRB3) pseudokinase plays a crucial role in cell proliferation, migration and morphogenesis during development. In our recent study, an introduction of human TRB3 gene into mouse mammary tumor cells caused an increase of proliferation of tumor cells and their nuclear size. In the current study, to examine whether this gene causes de novo morphological changes in a specific organ site we have developed a novel variation of the transgenic mouse model that conditionally expresses human TRB3 (hTRB3) gene using Cre-recombinase (Cre)/loxP recombination system. By injecting hTRB3 transgene construct into pronuclei of mouse embryo, we eventually obtained four hTRB3 mice. The gene expression was controlled by infection of adenovirus-expressing Cre via the tail vein of hTRB3 mouse. In Cre-mediated hTRB3 mouse, expression of the hTRB3 protein was detected in the cytoplasm of hepatocytes in the liver. Expression of this protein was also seen in lymphocytes in the spleen, glomerular endothelial cells, and epithelial cells of collecting duct of the kidney. In hepatocytes of the hTRB3 mouse, nuclear size was significantly greater than that of the wild type mouse, indicating that hTRB3 can play a role at least in part in hepatic morphogenesis. The present animal model may provide a system for evaluation of de novo morphological changes induced by a specific transgene in a specific organ site.Key words Tribbles related protein 3 (TRB3); transgenic mouse; Cre-recombinase (Cre)/loxP Tribbles related protein 3 (TRB3) is one of the mammalian homologues of Drosophila Tribbles. This molecule contains a serine/threonine kinase catalytic domain but lacks an ATP binding site or one of the conserved catalytic motifs essential for kinase activity.1-3) TRB3 has also been shown to be involved in multiple cellular processes such as glucose/lipid metabolism, muscle/adipocyte differentiation, and stress response by interacting with various functional proteins. 1,[3][4][5][6][7][8][9][10] Three mammalian Tribbles homologues, TRB1, TRB2, and TRB3 are crucial modulators of tumorigenesis.3,11-13) TRB1 and TRB2 induce acute myelogenous leukemia by inhibiting CCAAT/enhancer binding protein α (C/EBPα) function.
12)TRB3 is highly expressed in a wide range of human carcinoma cell lines and in several types of human carcinoma.
3,13)We have recently demonstrated that TRB3 promotes proliferation and induces polyploidy of mouse mammary tumor cells.14) This finding was likely to indicate TRB3's response to morphological function. In the current study, by utilizing the recombinant adenovirus expressing Cre-recombinase (Cre) system we examined whether human TRB3 gene causes de novo morphological changes in a specific organ site.
MATERIALS AND METHODS
Generation of Human TRB3 Transgenic MouseWe ligated flag-tagged full length human TRB3 (hTRB3) cDNA 7) into KpnI and SwaI restriction sites of pCALNL5 vector (DNA Bank, RIKEN Bio Resource Center, Ibaraki, Japan), [15][16][17] and this construct was termed pCALNL-flag-hTRB3. The pCALNL-fl...