Role of retinoic acid receptors α1 and γ in the response of murine limbs to retinol in vitro

Authors


  • Presented at the 45th Annual Meeting of the Teratology Society, St. Pete Beach, 2005.

Abstract

BACKGROUND

Derivatives of retinol (vitamin A), commonly referred to as retinoids, signal through retinoic acid and retinoid X receptors (RARs/RXRs) and are essential for normal limb formation. Retinoid imbalances or perturbations in receptor function result in aberrant limb development. To examine the mechanisms underlying retinol-induced limb defects, we determined the responsiveness of limbs from RARα1−/−γ mice to excess retinol in vitro.

METHODS

RARα1−/−γ+/− mice were bred and their embryos were recovered at gestational day (GD) 12.5. The forelimbs were excised and cultured in vitro in the presence of all-trans retinol acetate (0, 1.25, 12.5, or 62.5 μM) for 6 days. The expression profiles of genes known to affect chondrogenesis (sox9 and col2a1) and limb outgrowth (meis1, meis2, and pbx1a) were examined by real-time qRT-PCR following retinol exposure for 3 hr.

RESULTS

Whereas RARα1−/−γ+/+ and RARα1−/−γ+/− limbs exhibited deleterious effects on limb outgrowth and chondrogenesis in the presence of exogenous retinol, this outcome was significantly attenuated in RARα1−/−γ−/− limbs. The expressions of sox9 and col2a1 were significantly decreased in retinol-exposed RARα1−/−γ+/+ limbs. In contrast, expression was not altered in limbs from their RARα1−/−γ+/− or RARα1−/−γ−/− littermates. Retinol exposure upregulated the expression of meis1 and meis2 in RARα1−/−γ+/+ limbs; however, in RARα1−/−γ−/− limbs the expression of both genes was unresponsive to retinol. Pbx1a remained unresponsive to retinol treatment in all genotypes.

CONCLUSION

In the absence of RARα1, RARγ is a functionally important mediator of retinoid-induced limb dysmorphogenesis. Birth Defects Research (Part A), 2005. © 2005 Wiley-Liss, Inc.

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