The finding of DORV in GSK-3Cdeficient embryos may be interpreted as a nonspecific finding, as septation of the great vessels, creation of AV valves and outflow tracts, and closure of the VSD are regulated by cells of the endocardial cushions and neural crest. were born without a cardiac phenotype, no live-born pups were recovered. The embryos had a double outlet RV, ventricular septal defects, and hypertrophic myopathy, with near obliteration of the ventricular cavities. UNC-2025 The hypertrophic myopathy was caused by cardiomyocyte hyperproliferation without hypertrophy and was associated with increased expression and nuclear localization of three regulators of proliferation GATA4, cyclin D1, and c-Myc. These studies, which we believe are the first in mammals to examine the role of GSK-3 and GSK-3 in the heart using loss-of-function approaches, implicate GSK-3 as a central regulator of embryonic cardiomyocyte proliferation and differentiation, as well as of outflow tract development. Although controversy over the teratogenic effects of lithium remains, our studies suggest that caution should be exercised in the use of newer, more potent drugs targeting GSK-3 in women of childbearing age. Introduction The factors regulating proliferation of cardiomyocytes during development have been the focus of many investigations in the past decade. These studies have identified several growth factors, acting in a paracrine fashion, that regulate cardiac growth and chamber morphogenesis. Specifically, endothelium-derived neuregulin-1 (Nrg1), acting via its receptor and coreceptor, the tyrosine kinases Erb-B4 and Erb-B2, is critical for chamber morphogenesis and trabeculation of the ventricular walls (1C3). Other studies have recognized IGF-1 (4), retinoic acid, FGF9, -16, and -20 (5), and BMP10 (6) as regulators of cardiomyocyte proliferation during mid-gestation. These factors likely regulate cardiomyocyte proliferation through transcription factors, including N-myc, GATA4, T-box genes, and, probably, nuclear element of triggered T cells (NF-AT) family members (in particular, NF-ATc3 and NF-ATc4) (7C11). Signaling pathways linking growth factors and these downstream mediators of proliferation are poorly understood. Not surprisingly, the PI3K pathway, which is the main signaling arm of several growth element receptors, including IGF-1, has been found to play a role in cardiomyocyte proliferation ex lover vivo and in vitro (4, 12, 13). However, it remains unclear whether this is relevant in vivo, which specific components of this complex pathway might regulate growth, and how they accomplish this, particularly in the developing heart. The glycogen synthase kinase isoforms GSK-3 and GSK-3 have nearly identical kinase domains but differ in their N- and C-terminal sequences (14, 15). These kinases are key regulators of the canonical Wnt pathway through phosphorylation-mediated focusing on of -catenin for proteasomal degradation (16C19). The Wnt/-catenin pathway takes on a central part in endocardial cushioning and atrioventricular valve development via regulating the process of endothelial-mesenchymal transition (EMT) (16, 19). Indeed, proper rules of canonical Wnt pathway parts, including dishevelled-2, is required for outflow tract development (20, 21). However, isoform-specific tasks for GSK-3 and -3 in Wnt/-cateninCregulated heart development are unlikely, since both kinases are functionally redundant in regulating -catenin stability and 3 of 4 GSK-3 alleles must be disrupted before an effect on -catenin signaling can be found (22). GSK-3 kinases have also been reported to negatively regulate several transcription factors and fundamental cell cycle regulators implicated in heart development, such as D-type cyclins and Myc family members (23, 24). However, the studies suggesting a role for GSK-3 in regulating these factors are largely based on overexpression methods in cultured cell lines, and, recently, some have challenged the putative part played by GSK-3 (25C27). We believed that determining the role played by GSK-3 in cardiac development was an important issue in and of itself, but the question may take on higher importance given the proposed use of small molecule inhibitors of GSK-3 in ladies of childbearing age who suffer from bipolar disorder. It is estimated that nearly 4% of the US population suffers from bipolar disorder (28), and inhibition of GSK-3 is definitely believed to perform a key part in the restorative response to lithium treatment (29), which has been the mainstay of therapy for 50 years. Based on the preponderance of evidence (examined in ref. 29), GSK-3 has been identified as a viable target for treatment of bipolar disorder. Since there is a suggestive link between lithium therapy and congenital cardiac malformations (30), Rabbit Polyclonal to FER (phospho-Tyr402) the active UNC-2025 development of newer GSK-3 inhibitors that are significantly more potent than lithium increases the.By comparison, no live-born animals were recovered. Previously, embryos were found to be susceptible to liver failure in utero. ventricular septal problems, and hypertrophic myopathy, with near obliteration of the ventricular cavities. The hypertrophic myopathy was caused by cardiomyocyte hyperproliferation without hypertrophy and was associated with improved manifestation and nuclear localization of three regulators of proliferation GATA4, cyclin D1, and c-Myc. These studies, which we believe are the 1st in mammals to analyze the part of GSK-3 and GSK-3 in the heart using loss-of-function methods, implicate GSK-3 like a central regulator of embryonic cardiomyocyte proliferation and differentiation, as well as of outflow tract development. Although controversy on the teratogenic effects of lithium remains, our studies suggest that caution should be exercised in the use of newer, more potent drugs focusing on GSK-3 in ladies of childbearing age. Introduction The factors regulating proliferation of cardiomyocytes during development have been the focus of many investigations in the past decade. These studies have identified several growth factors, acting inside a paracrine fashion, that regulate cardiac growth and chamber morphogenesis. Specifically, endothelium-derived neuregulin-1 (Nrg1), acting via its receptor and coreceptor, the tyrosine kinases Erb-B4 and Erb-B2, is critical for chamber morphogenesis and trabeculation of the ventricular walls (1C3). Other studies have recognized IGF-1 (4), retinoic acid, FGF9, -16, and -20 (5), and BMP10 (6) as regulators of cardiomyocyte proliferation during mid-gestation. These factors likely regulate cardiomyocyte proliferation through transcription factors, including N-myc, GATA4, T-box genes, and, probably, nuclear element of triggered T cells (NF-AT) family members (in particular, NF-ATc3 and NF-ATc4) (7C11). Signaling UNC-2025 pathways linking growth factors and these downstream mediators of proliferation are poorly understood. Not surprisingly, the PI3K pathway, which is the main signaling arm of several growth element receptors, including IGF-1, has been found to play a role in cardiomyocyte proliferation ex lover vivo and in vitro (4, 12, 13). However, it remains unclear whether this is relevant in vivo, which specific components of this complex pathway might regulate growth, and how they accomplish this, particularly in the developing heart. The glycogen synthase kinase isoforms GSK-3 and GSK-3 have nearly identical kinase domains but differ in their N- and C-terminal sequences (14, 15). These kinases are key regulators of the canonical Wnt pathway through phosphorylation-mediated focusing on of -catenin for proteasomal degradation (16C19). The Wnt/-catenin pathway takes on a central part in endocardial cushioning and atrioventricular valve development via regulating the process of endothelial-mesenchymal transition (EMT) (16, 19). Indeed, proper rules of canonical Wnt pathway UNC-2025 parts, including dishevelled-2, is required for outflow tract development (20, 21). However, isoform-specific tasks for GSK-3 and -3 in Wnt/-cateninCregulated heart development are unlikely, since both kinases are functionally redundant in regulating -catenin stability and 3 of 4 GSK-3 alleles must be disrupted before an effect on -catenin signaling can be found (22). GSK-3 kinases have also been reported to negatively regulate several transcription factors and fundamental cell cycle regulators implicated in heart development, such as D-type cyclins UNC-2025 and Myc family members (23, 24). However, the studies suggesting a role for GSK-3 in regulating these factors are largely based on overexpression methods in cultured cell lines, and, recently, some have challenged the putative part played by GSK-3 (25C27). We believed that determining the part played by GSK-3 in cardiac development was an important issue in and of itself, but the question may take on higher importance given the proposed use of small molecule inhibitors of GSK-3 in ladies of childbearing age who suffer from bipolar disorder. It is estimated that nearly 4% of the US population suffers from bipolar disorder (28), and inhibition of GSK-3 is definitely believed to perform a key part in the restorative response to lithium treatment (29), which has been the mainstay of therapy for 50 years. Based on the preponderance of evidence (examined in ref. 29), GSK-3 has been identified as a viable target for treatment of bipolar disorder. Since there is a suggestive link between lithium therapy and congenital cardiac malformations (30), the active development of newer GSK-3 inhibitors that are significantly more potent than lithium increases the importance of defining the part of GSK-3 in cardiac development. To determine the part of GSK-3 kinases in general, and specific isoforms in particular, in mammalian heart development, we analyzed Sera cells and mice erased for either or Sera cell lines (22). Spontaneously contracting WT and EBs were found after 7 days. However, beating EBs were not found until day time 8. Compared with WT (82 beating per 93 EBs,88%), there were significantly fewer beating EBs (66 beating per.
