ABSTRACT
Coronary artery anomalies are common congenital disorders with serious consequences in adult life. Coronary circulation begins when the coronary stems form connections between the aorta and the developing vascular plexus. We recently identified the WNT signaling modulator R-spondin 3 (Rspo3), as a crucial regulator of coronary stem proliferation. Using expression analysis and tissue-specific deletion we now demonstrate that Rspo3 is primarily produced by cardiomyocytes. Moreover, we have employed CRISPR/Cas9 technology to generate novel Lgr4-null alleles that showed a significant decrease in coronary stem proliferation and thus phenocopied the coronary artery defects seen in Rspo3 mutants. Interestingly, Lgr4 mutants displayed slightly hypomorphic right ventricles, an observation also made after myocardial specific deletion of Rspo3. These results shed new light on the role of Rspo3 in heart development and demonstrate that LGR4 is the principal R-spondin 3 receptor in the heart.
Subject(s)
Coronary Vessels/embryology , Heart/embryology , Myocytes, Cardiac/metabolism , Receptors, G-Protein-Coupled/metabolism , Thrombospondins/metabolism , Wnt Signaling Pathway/physiology , Animals , Coronary Circulation/physiology , Coronary Vessels/cytology , Mice , Mice, Transgenic , Myocytes, Cardiac/cytology , Receptors, G-Protein-Coupled/genetics , Thrombospondins/geneticsABSTRACT
Coronary arteries are essential to support the heart with oxygen, and coronary heart disease is one of the leading causes of death worldwide. The coronary arteries form at highly stereotyped locations and are derived from the primitive vascular plexus of the heart. How coronary arteries are remodeled and the signaling molecules that govern this process are poorly understood. Here, we have identified the Wnt-signaling modulator Rspo3 as a crucial regulator of coronary artery formation in the developing heart. Rspo3 is specifically expressed around the coronary stems at critical time points in their development. Temporal ablation of Rspo3 at E11.5 leads to decreased ß-catenin signaling and a reduction in arterial-specific proliferation. As a result, the coronary stems are defective and the arterial tree does not form properly. These results identify a mechanism through which localized expression of RSPO3 induces proliferation of the coronary arteries at their stems and permits their formation.
Subject(s)
Coronary Vessels/growth & development , Coronary Vessels/metabolism , Thrombospondins/biosynthesis , Animals , Cell Proliferation/physiology , Female , Mice , Neovascularization, Physiologic/physiology , Pregnancy , Wnt Signaling PathwayABSTRACT
Kidney organogenesis requires the tight control of proliferation, differentiation and apoptosis of renal progenitor cells. How the balance between these cellular decisions is achieved remains elusive. The Wilms' tumour suppressor Wt1 is required for progenitor survival, but the molecular cause for renal agenesis in mutants is poorly understood. Here we demonstrate that lack of Wt1 abolishes fibroblast growth factor (FGF) and induces BMP/pSMAD signalling within the metanephric mesenchyme. Addition of recombinant FGFs or inhibition of pSMAD signalling rescues progenitor cell apoptosis induced by the loss of Wt1. We further show that recombinant BMP4, but not BMP7, induces an apoptotic response within the early kidney that can be suppressed by simultaneous addition of FGFs. These data reveal a hitherto unknown sensitivity of early renal progenitors to pSMAD signalling, establishes FGF and pSMAD signalling as antagonistic forces in early kidney development and places WT1 as a key regulator of pro-survival FGF signalling pathway genes.
Subject(s)
Fibroblast Growth Factors/metabolism , Repressor Proteins/metabolism , Animals , Bone Morphogenetic Proteins/genetics , Bone Morphogenetic Proteins/metabolism , Cell Differentiation/genetics , Cell Differentiation/physiology , Computational Biology , Fibroblast Growth Factors/genetics , Fluorescent Antibody Technique , Gene Expression Regulation, Developmental/genetics , Gene Expression Regulation, Developmental/physiology , In Situ Hybridization , In Situ Nick-End Labeling , Mice , Mice, Mutant Strains , Organ Culture Techniques , Repressor Proteins/genetics , Reverse Transcriptase Polymerase Chain Reaction , Signal Transduction/genetics , Signal Transduction/physiology , Stem Cells/metabolism , WT1 ProteinsABSTRACT
Adrenal glands and gonads share a common primordium (AGP), but the molecular events driving differentiation are poorly understood. Here we demonstrate that the Wilms tumor suppressor WT1 is a key factor defining AGP identity by inhibiting the steroidogenic differentiation process. Indeed, ectopic expression of WT1 precludes differentiation into adrenocortical steroidogenic cells by locking them into a progenitor state. Chromatin immunoprecipitation experiments identify Tcf21 and Gli1 as direct targets of WT1. Moreover, cell lineage tracing analyses identify a long-living progenitor population within the adrenal gland, characterized by the expression of WT1, GATA4, GLI1, and TCF21, that can generate steroidogenic cells in vivo. Strikingly, gonadectomy dramatically activates these WT1(+) cells and leads to their differentiation into gonadal steroidogenic tissue. Thus, our data describe a mechanism of response to organ loss by recreating hormone-producing cells at a heterotopic site.
