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 6

Excessive RA due to loss of Tlx1 causes premature differentiation and reduced vasculogenesis.

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Excessive RA due to loss of Tlx1 causes premature differentiation and re...
(A) Heat map and validation of Desmin expression by qPCR in E13.5 Tlx1+/– and Tlx1–/– spleens (left). Confocal images of E13.5 spleen sagittal sections stained with anti-desmin antibody (green) (middle). Nuclei are visualized by DAPI staining (blue). Dashed red lines indicate the developing spleen. Data are representative of 1 embryo of 5 embryos analyzed for each genotype. Desmin expression by qPCR in primary E13.5 spleen mesenchymal cells after 48 hours of RA treatment (right). Data are representative of 1 of 2 independent experiments. (B) Expression of Vegf-a in primary E13.5 spleen mesenchymal cells treated for 48 hours with RA or control vehicle. Heat map and validation of Vegf-a expression by qPRCs in E13.5 Tlx1+/– and Tlx1–/– spleens. Data are representative of 1 of 2 independent experiments. IHC analysis on E13.5 Tlx1+/– and Tlx1–/– sagittal sections stained with anti–PECAM-1 antibody to reveal vascular networks and counterstained with hematoxylin to show nuclei. Microvessel density was calculated by counting of the number of PECAM-1+ vessels/μm2 in Tlx1+/– and Tlx1–/– embryonic spleen. Data are representative of 1 embryo of 5 embryos analyzed for each genotype. (C) Representative confocal images of E13.5 Tlx1+/– and Tlx1–/– spleen sagittal sections stained with anti–PECAM-1 antibody (red) to reveal endothelial cells and anti–β-gal antibody (green) to show TLX1-expressing cells in Tlx1-LacZ knock-in embryos. Nuclei are visualized by DAPI staining (blue). Data are representative of 1 embryo of 5 embryos analyzed for each genotype. (A and B) The means of triplicates ± SD are shown, *P < 0.05 (B), **P < 0.01 (A and B) (2-tailed Student’s t test). (A–C) Scale bars: 50 μm. st, stomach; sp, spleen.