Abstract: Disclosed are epicardium-derived mesenchymal cells (EPDCs) that differentiate to fates that are commonly adopted by mesenchymal cells elsewhere in the body, but not currently associated with the epicardium. Also disclosed are methods, systems and assays relating to adipocyte and/or osteogenic differentiation in EPDCs that are often related to disease or disregulated states, i.e. the “atypical” fates of epicardium-derived cells. Disclosed are specific EPDC cells that model both the typical fates and atypical fates of EPDCs, and resultant uses of such EPDC cells in systems, methods, compositions and drug discovery.

Abstract: DNA segments have been discovered, and characterized by sequence, which are response elements operative to confer responsiveness to ligands for several members of the steroid/thyroid superfamily of receptors, for the transcriptional activation and/or repression of promoters in cells. By using transcriptional control regions comprising response elements of the present invention in combination with a functional promoter, it is now possible to provide recombinant DNA vectors containing a gene, the transcription (and, thereby, also expression) of which is under the control of a promoter, the transcriptional activity of which is responsive to ligands for members of the steroid/thyroid superfamily of receptors.

Abstract: DNA segments have been discovered, and characterized by sequence, which are response elements operative to confer responsiveness to ligands for several members of the steroid/thyroid superfamily of receptors, for the transcriptional activation and/or repression of promoters in cells. By using transcriptional control regions comprising response elements of the present invention in combination with a functional promoter, it is now possible to provide recombinant DNA vectors containing a gene, the transcription (and, thereby, also expression) of which is under the control of a promoter, the transcriptional activity of which is responsive to ligands for members of the steroid/thyroid superfamily of receptors.

Abstract: DNA segments have been discovered, and characterized by sequence, which are response elements operative to confer responsiveness to ligands for several members of the steroid/thyroid superfamily of receptors, for the transcriptional activation and/or repression of promoters in cells. By using transcriptional control regions comprising response elements of the present invention in combination with a functional promoter, it is now possible to provide recombinant DNA vectors containing a gene, the transcription (and, thereby, also expression) of which is under the control of a promoter, the transcriptional activity of which is responsive to ligands for members of the steroid/thyroid superfamily of receptors.

Abstract: In accordance with the present invention, there are provided targeted loss of function mutant mice which express less than endogenous levels of at least one member of the steroid/thyroid superfamily of receptors in at least one specific tissue type. For example, mutations in the RXR&agr; gene in mouse germlines are lethal in the embryonic stage between E13.5 and E16.5 when bred to homozygosity. The major defect responsible for this lethal effect is hypoplastic development of the ventricular chambers of the heart, which is manifest as a grossly thinned ventricular wall with concurrent defects in ventricular septation. This phenotype is identical to a subset of the effects of embryonic vitamin A deficiency, and therefore establishes RXR&agr; as a genetic component of the vitamin A signaling pathway in cardiac morphogenesis.

Abstract: The present invention provide transcriptional control regions, expression vectors comprising said regions, mammalian cells transformed to transcribe and express genes from said vectors, and various methods of assaying compounds for hormone agonist or antagonist activity, all based on discovery of response elements of the .beta.-retinoic acid receptor and of the activation of said response elements in all mammalian cells without need to transform the cells to express the receptor independently of endogenous expression thereof.