Reduced intestinal ALP activity in villin-HDAC3 transgenic mice

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Inhibitors of histone deacetylases (HDACs) have well-established effects on cell maturation, such as growth arrest, apoptosis induction and promotion of differentiation, in tumor cell lines cultured in vitro. We have previously demonstrated that the Class I HDAC, HDAC3, promotes the growth and survival, and inhibits differentiation of, human colon cancer cells in vitro (Wilson et al. J. Biol. Chem. 281:13548-5810, 2006). HDAC3 is maximally expressed in the proliferative zone of normal mouse and human intestinal epithelium, and is downregulated in the villus. To determine whether downregulation of HDAC3 is required for normal intestinal cell maturation in vivo, we examined the effect of maintaining HDAC3 expression along the entire length of the crypt-villus axis by generating a villin-HDAC3 transgenic mouse. Pronuclei from FvB mice were injected with a villin-HDAC3-myc/his construct and 2 independent strains of transgenic mice with intestinal-specific overexpression of HDAC3 were generated. Germline transmission of the transgene was confirmed in both strains. Intestinal-specific expression of the transgene was confirmed by Western Blot detection of the myc tag. Western Blot analysis of cells fractionated along the crypt-villus axis, and immunohistochemical staining, demonstrated sustained HDAC3 expression along the entire crypt-villus axis of transgenic mice, in contrast to the predominantly crypt-localized expression in wild-type mice. No differences in weight or life-span were observed between transgenic and wild-type littermates. While no significant alteration in intestinal architecture, as assessed by H&E staining, Ki67 staining (proliferation) and Alcian Blue staining (Goblet cells), was observed in transgenic mice, alkaline phosphatase (ALP) activity was significantly reduced (50% reduction, p < 0.05, n = 4) in the crypts and villi of transgenic mice compared to wild-type littermates at 3 and 6 months of age. The role of HDAC3 in intestinal tumorigenesis is presently being assessed by crossing HDAC3-Tg mice with Apc1638 mice.