Regulation of RXR-RAR Heterodimers by RXR- and RAR-Specific Ligands and Their Combinations

The three subtypes (α, β, and γ) of the retinoic acid receptor (RAR) are ligand-dependent transcription factors that mediate retinoic acid signaling by forming heterodimers with the retinoid X receptor (RXR). Heterodimers are functional units that bind ligands (retinoids), transcriptional co-regulators and DNA, to regulate gene networks controlling cell growth, differentiation, and death. Using biochemical, crystallographic, and cellular approaches, we have set out to explore the spectrum of possibilities to regulate RXR-RAR heterodimer-dependent transcription through various pharmacological classes of RAR- and RXR- specific ligands, alone or in combination. We reveal the molecular details by which these compounds direct specificity and functionality of RXR-RAR heterodimers. Among these ligands, we have reevaluated and improved the molecular and structural definition of compounds CD2665, Ro41-5253, LE135, or LG100754, highlighting novel functional features of these molecules. Our analysis reveals a model of RXR-RAR heterodimer action in which each subunit retains its intrinsic properties in terms of ligand and co-regulator binding. However, their interplay upon the combined action of RAR- and RXR-ligands allows for the fine tuning of heterodimer activity. It also stresses the importance of accurate ligand characterization to use synthetic selective retinoids appropriately and avoid data misinterpretations.

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Roles of retinoic acid receptors in early embryonic morphogenesis and hindbrain patterning

Development ◽

10.1242/dev.128.11.2031 ◽

2001 ◽

Vol 128 (11) ◽

pp. 2031-2038 ◽

Cited By ~ 4

Author(s):

Olivia Wendling ◽

Norbert B. Ghyselinck ◽

Pierre Chambon ◽

Manuel Mark

Keyword(s):

Retinoic Acid ◽

Retinoic Acid Receptor ◽

Axial Rotation ◽

Retinoic Acid Receptors ◽

Retinoic Acid Signaling ◽

Wild Type ◽

Pharyngeal Arches ◽

Embryonic Morphogenesis ◽

Null Mutants

Mutants mice carrying targeted inactivations of both retinoic acid receptor (RAR) α and RARγ (Aα/Aγ mutants) were analyzed at different embryonic stages, in order to establish the timing of appearance of defects that we previously observed during the fetal period. We show that embryonic day (E)9.5 Aα/Aγ embryos display severe malformations, similar to those already described in retinaldehyde dehydrogenase 2 null mutants. These malformations reflect early roles of retinoic acid signaling in axial rotation, segmentation and closure of the hindbrain; formation of otocysts, pharyngeal arches and forelimb buds; and in the closure of the primitive gut. The hindbrain of E8.5 Aα/Aγ embryos shows a posterior expansion of rhombomere 3 and 4 (R3 and R4) markers, but fails to express kreisler, a normal marker of R5 and R6. This abnormal hindbrain phenotype is strikingly different from that of embryos lacking RARα and RARβ (Aα/Aβmutants), in which we have previously shown that the territory corresponding to R5 and R6 is markedly enlarged. Administration of a pan-RAR antagonist at E8.0 to wild-type embryos cultured in vitro results in an Aα/Aβ-like hindbrain phenotype, whereas an earlier treatment at E7.0 yields an Aα/Aγ-like phenotype. Altogether, our data suggest that RARα and/or RARγ transduce the RA signal that is required first to specify the prospective R5/R6 territory, whereas RARβ is subsequently involved in setting up the caudal boundary of this territory.

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Impact of sustained TGFβ receptor inhibition on chromatin accessibility and gene expression in cultured human endometrial MSC

10.1101/2020.05.01.073346 ◽

2020 ◽

Author(s):

Raffaella Lucciola ◽

Pavle Vrljicak ◽

Caitlin Filby ◽

Saeedeh Darzi ◽

Shanti Gurung ◽

...

Keyword(s):

Gene Expression ◽

Retinoic Acid ◽

Gene Networks ◽

Large Scale ◽

Transforming Growth Factor ◽

Retinoic Acid Receptor ◽

Human Endometrium ◽

Acid Receptor ◽

Genome Wide ◽

The Impact

AbstractEndometrial mesenchymal stem cells (eMSC) drive the extraordinary regenerative capacity of the human endometrium. Clinical application of eMSC for therapeutic purposes is hampered by spontaneous differentiation and cellular senescence upon large-scale expansion in vitro. A83-01, a selective transforming growth factor-β receptor (TGFβ-R) inhibitor, promotes pharmacological expansion of eMSC in culture by blocking differentiation and senescence, but the underlying mechanisms are incompletely understood. In this study, we combined RNA-seq and ATAC-seq to study the impact of sustained TGFβ-R inhibition on gene expression and chromatin architecture of eMSC. Treatment of primary eMSC with A83-01 for 5 weeks resulted in differential expression of 1,463 genes. Gene ontology analysis showed enrichment of genes implicated in cell growth whereas extracellular matrix genes and genes involved in cell fate commitment were downregulated. ATAC-seq analysis demonstrated that sustained TGFβ-R inhibition results in opening and closure of 3,555 and 2,412 chromatin loci, respectively. Motif analysis revealed marked enrichment of retinoic acid receptor (RAR) binding sites, which was paralleled by the induction of RARB, encoding retinoic acid receptor beta (RARβ). Selective RARβ inhibition attenuated proliferation and clonogenicity of A83-01 treated eMSC. Taken together, our study provides new insights into the gene networks and genome-wide chromatin changes that underpin maintenance of an undifferentiated phenotype of eMSC in prolonged culture.Significance statementCycling human endometrium is a rich source of adult stem/progenitor cells that could be exploited for clinical purposes. Small molecules, such as A83-01, that modulate cell identity may open new avenues to maintain the functional properties of eMSC upon expansion in culture. By integrating complementary genome-wide profiling techniques, we mapped the dynamic changes in chromatin landscape and gene expression in response to prolonged A83-01 treatment of eMSC. Our findings provide new insights into the mechanisms of action of TGFβ-R inhibition that may lead to the development of more targeted pharmacological approaches for MSC expansion.

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