Project description: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 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 insight into the molecular determinants of human congenital asplenia.
Project description:The molecular mechanisms underlying asplenia, a condition often associated with overwhelming infections remain largely unknown. During spleen development, the transcription factor TLX1 controls morphogenesis and organ expansion, and loss of it causes spleen agenesis. However, the downstream signaling pathways that are deregulated in the absence of TLX1 are mostly unknown. Herein, we demonstrate that loss of Tlx1 in the splenic mesenchyme causes increased retinoic acid (RA) signaling. Increased RA activity causes premature differentiation of the splenic mesenchyme and reduced vasculogenesis of the splenic anlage. Moreover, excess or deficiency in RA signaling, as observed in Cyp26b1 or Rdh10 mutants respectively, also results in spleen growth arrest. Genome-wide analysis revealed that TLX1 binds RA-associated genes through the AP-1 site and cooperates with the AP-1 family transcription factors to regulate transcription. Pharmacological inhibition of RA signaling partially rescues the spleen defect. These findings establish the critical role of TLX1 in controlling RA metabolism, and provide novel mechanistic insights into the molecular determinants underlying congenital asplenia.
Project description:The molecular mechanisms underlying asplenia, a condition often associated with overwhelming infections remain largely unknown. During spleen development, the transcription factor TLX1 controls morphogenesis and organ expansion, and loss of it causes spleen agenesis. However, the downstream signaling pathways that are deregulated in the absence of TLX1 are mostly unknown. Herein, we demonstrate that loss of Tlx1 in the splenic mesenchyme causes increased retinoic acid (RA) signaling. Increased RA activity causes premature differentiation of the splenic mesenchyme and reduced vasculogenesis of the splenic anlage. Moreover, excess or deficiency in RA signaling, as observed in Cyp26b1 or Rdh10 mutants respectively, also results in spleen growth arrest. Genome-wide analysis revealed that TLX1 binds RA-associated genes through the AP-1 site and cooperates with the AP-1 family transcription factors to regulate transcription. Pharmacological inhibition of RA signaling partially rescues the spleen defect. These findings establish the critical role of TLX1 in controlling RA metabolism, and provide novel mechanistic insights into the molecular determinants underlying congenital asplenia. Samples: 3 replicates of E13.5 spleens from Tlx1 heterozygous embryos were compared to 3 replicates of E13.5 spleens from Tlx1 homozygous embryos
Project description: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 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 insight into the molecular determinants of human congenital asplenia. We performed ChIP-sequencing for Hox11 rep1 and rep2 in eSMC untreated cells.
Project description: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.
Project description:The T-cell leukemia homeobox 1 (TLX1, HOX11) transcription factor is critically involved in the multistep pathogenesis of T-cell acute lymphoblastic leukemia (T-ALL) and often cooperates with NOTCH1 activation during malignant T-cell transformation. However, the exact molecular mechanisms by which these T-cell specific oncogenes cooperate during transformation remain to be established. Here, we used an integrative genomics approach to show that the oncogenic properties of TLX1 are mediated by genome-wide interference with the ETS1 and RUNX1 transcription factors. Partial disruption of ETS1 and RUNX1 activity by ectopic TLX1 expression in immature thymocytes drives repression of T-cell specific super-enhancers and mediates an unexpected transcriptional antagonism with NOTCH1 signaling. These phenomena coordinately trigger a TLX1 driven pre-leukemic phenotype in human thymic precursor cells, which corresponds with the in vivo thymic regression observed in murine TLX1 tumor models, and creates a strong genetic pressure for acquiring activating NOTCH1 mutations as a prerequisite for full leukemic transformation. In conclusion, our results uncover a functional antagonism between cooperative oncogenes during the earliest phases of tumor development and provide novel insights in the multistep pathogenesis of TLX1 driven human leukemia.