Transcription factor TLX1 controls retinoic acid signaling to ensure spleen development
Elisa Lenti, … , Paul A. Trainor, Andrea Brendolan
Elisa Lenti, … , Paul A. Trainor, Andrea Brendolan
Published May 23, 2016
Citation Information: J Clin Invest. 2016;126(7):2452-2464. https://doi.org/10.1172/JCI82956.
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Transcription factor TLX1 controls retinoic acid signaling to ensure spleen development

Abstract

The molecular mechanisms that underlie spleen development and congenital asplenia, a condition linked to increased risk of overwhelming infections, remain largely unknown. The transcription factor TLX1 controls cell fate specification and organ expansion during spleen development, and Tlx1 deletion causes asplenia in mice. Deregulation of TLX1 expression has recently been proposed in the pathogenesis of congenital asplenia in patients carrying mutations of the gene-encoding transcription factor SF-1. Herein, we have shown that TLX1-dependent regulation of retinoic acid (RA) metabolism is critical for spleen organogenesis. In a murine model, loss of Tlx1 during formation of the splenic anlage increased RA signaling by regulating several genes involved in RA metabolism. Uncontrolled RA activity resulted in premature differentiation of mesenchymal cells and reduced vasculogenesis of the splenic primordium. Pharmacological inhibition of RA signaling in Tlx1-deficient animals partially rescued the spleen defect. Finally, spleen growth was impaired in mice lacking either cytochrome P450 26B1 (Cyp26b1), which results in excess RA, or retinol dehydrogenase 10 (Rdh10), which results in RA deficiency. Together, these findings establish TLX1 as a critical regulator of RA metabolism and provide mechanistic insights into the molecular determinants of human congenital asplenia.

Authors

Elisa Lenti, Diego Farinello, Kazunari K. Yokoyama, Dmitry Penkov, Laura Castagnaro, Giovanni Lavorgna, Kenly Wuputra, Lisa L. Sandell, Naomi E. Butler Tjaden, Francesca Bernassola, Nicoletta Caridi, Anna De Antoni, Michael Wagner, Katja Kozinc, Karen Niederreither, Francesco Blasi, Diego Pasini, Gregor Majdic, Giovanni Tonon, Paul A. Trainor, Andrea Brendolan

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Figure 5

RA induces the expression of cell cycle inhibitors and growth arrest.

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RA induces the expression of cell cycle inhibitors and growth arrest. (A...
(A) Growth curve analysis of primary E13.5 spleen mesenchymal cells treated with RA or control vehicle (left). The means of triplicates ± SD are shown, *P < 0.05 (2-way ANOVA). Data are representative of 1 of 3 independent experiments. Expression of Cdkn2b/p15 in primary E13.5 spleen mesenchymal cells treated for 3 or 5 days with RA or control vehicle (middle). The means of triplicates ± SD are shown, **P < 0.01, ***P < 0.001 (2-tailed Student’s t test). Data are representative of 1 of 2 independent experiments. Heat map and validation of Cdkn2b/p15 expression by qPCR in E13.5 Tlx1+/– and Tlx1–/– spleens (right). The means of triplicates ± SD are shown, **P < 0.01 (2-tailed Student’s t test). Data are representative of 1 of 2 independent validation experiments. (B) Bright-field images of E13.5 explanted spleens cultured in the presence of RA or vehicle (DMSO). Arrows indicate mesenchymal cell sprouting. Quantification of the spleen size area (%) was calculated using ImageJ, as the ratio of spleen area at 24 hours versus 0 hours. The means of triplicates ± SD are shown, **P < 0.01 (2-tailed Student’s t test). Data are representative of 1 of 3 independent experiments with 8 explanted spleens for each condition.