Retinoid signaling competence and RAR?-mediated gene regulation in the developing mammalian telencephalon

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Abstract
To study retinoid signaling in the developing telencephalon, we transfected a retinoid reporter gene into different regions of developing telencephalon. We found that the ventral telencephalon was more competent to retinoid signaling than the dorsal telencephalon. Moreover, among all retinoic acid receptors (RARs) and retinoid X receptors (RXRs), RARβ was strongly induced by retinoic acid in the ventral telencephalon, suggesting that RARβ might be involved in retinoid signaling competence. The RT‐PCR analysis indicated that RARβ was selectively expressed in the developing striatum of ventral telencephalon. We then demonstrated that null mutations of RARβ gene resulted in reduction of striatal‐enriched tyrosine phosphatase (STEP) mRNA in the striatum of RARβ−/− mutant mice. Conversely, the gain‐of‐function study showed that ectopic expression of RARβ1 in the cerebral cortex enhanced STEP expression, and the effect was RARβ‐isoform specific. Our study identified RARβ as an important molecule for transducing retinoid signals in developing ventral telencephalon. Developmental Dynamics 232:887–900, 2005.