T-box3 is a ciliary protein and regulates stability of the Gli3 transcription factor to control digit number.
Ontology highlight
ABSTRACT:
SUBMITTER: Emechebe U
PROVIDER: S-EPMC4829432 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:WNT signaling is critical in most aspects of skeletal development and homeostasis, and antagonists of WNT signaling are emerging as key regulatory proteins with great promise as therapeutic agents for bone disorders. Here we show that Sost and its paralog Sostdc1 emerged through ancestral genome duplication and their expression patterns have diverged to delineate non-overlapping domains in most organ systems including musculoskeletal, cardiovascular, nervous, digestive, reproductive and respiratory. In the developing limb, Sost and Sostdc1 display dynamic expression patterns with Sost being restricted to the distal ectoderm and Sostdc1 to the proximal ectoderm and the mesenchyme. While Sostdc1(-/-) mice lack any obvious limb or skeletal defects, Sost(-/-) mice recapitulate the hand defects described for Sclerosteosis patients. However, elevated WNT signaling in Sost(-/-); Sostdc1(-/-) mice causes misregulation of SHH signaling, ectopic activation of Sox9 in the digit 1 field and preaxial polydactyly in a Gli1- and Gli3-dependent manner. In addition, we show that the syndactyly documented in Sclerosteosis is present in both Sost(-/-) and Sost(-/-); Sostdc1(-/-) mice, and is driven by misregulation of Fgf8 in the AER, a region lacking Sost and Sostdc1 expression. This study highlights the complexity of WNT signaling in skeletal biology and disease and emphasizes how redundant mechanism and non-cell autonomous effects can synergize to unveil new intricate phenotypes caused by elevated WNT signaling.
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Project description:Inactivation of Gli3, a key component of Hedgehog signaling in vertebrates, results in formation of additional digits (polydactyly) during limb bud development. The analysis of mouse embryos constitutively lacking Gli3 has revealed the essential GLI3 functions in specifying the anteroposterior (AP) limb axis and digit identities. We conditionally inactivated Gli3 during mouse hand plate development, which uncoupled the resulting preaxial polydactyly from known GLI3 functions in establishing AP and digit identities. Our analysis revealed that GLI3 directly restricts the expression of regulators of the G(1)-S cell-cycle transition such as Cdk6 and constrains S phase entry of digit progenitors in the anterior hand plate. Furthermore, GLI3 promotes the exit of proliferating progenitors toward BMP-dependent chondrogenic differentiation by spatiotemporally restricting and terminating the expression of the BMP antagonist Gremlin1. Thus, Gli3 is a negative regulator of the proliferative expansion of digit progenitors and acts as a gatekeeper for the exit to chondrogenic differentiation.
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Project description:The anterior-posterior patterning of the vertebrate limb bud requires closely coordinated signaling interactions, including Sonic Hedgehog (Shh)-mediated counteraction of the Gli3 transcription factor in the distal and posterior mesenchyme of the limb bud. Suppressor of Fused (Sufu), an intracellular negative regulator of Shh signaling via Gli2 and Gli3, is implicated in early development of the mouse limb bud. However, how Sufu is involved in the genetic regulation of limb bud patterning still remains elusive. In this study, we show that the conditional deletion of Sufu in the mesenchyme of the early limb bud results in polydactyly with loss of digit identity and supernumerary bones in the wrist and the ankle. These pattern alterations are associated with anterior expansion of HoxD genes located at the 5' end of the cluster. By focusing on gene expression analysis of Shh/Gremlin1/Fgf signaling critical for the establishment and maintenance of anterior-posterior patterning, we show that early response to loss of Sufu involves anterior prolongation of Fgf4 and Fgf8 expression in the apical ectodermal ridge at E10.5. We also reveal the anterior activation of Shh-dependent posterior markers Ptc1, Gli1 and Gremlin in limb buds lacking Sufu. Furthermore, we find that loss of Sufu leads to attenuated levels of repressor Gli2 and repressor Gli3 in the early limb bud. Moreover, expression of Hand2 is activated in the entire limb bud at the early outgrowth stage in the mutant lacking Sufu. Thus, we provide evidence that Sufu is involved in the genetic network that restricts the posterior expression of Gli2/3/Hand2 and Gremlin/Fgf in limb bud patterning.
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Project description:The Gli transcription factors are mediators of Hedgehog (Hh) signaling and have been shown to play critical roles during embryogenesis. Previously, we have demonstrated that the Hh pathway is reactivated by ischemia in adult mammals, and that this pathway can be stimulated for therapeutic benefit; however, the specific roles of the Gli transcription factors during ischemia-induced Hh signaling have not been elucidated.To investigate the role of Gli3 in ischemic tissue repair.Gli3-haploinsufficient (Gli3(+/-)) mice and their wild-type littermates were physiologically similar in the absence of ischemia; however, histological assessments of capillary density and echocardiographic measurements of left ventricular ejection fractions were reduced in Gli3(+/-) mice compared to wild-type mice after surgically induced myocardial infarction, and fibrosis was increased. Gli3-deficient mice also displayed reduced capillary density after induction of hindlimb ischemia and an impaired angiogenic response to vascular endothelial growth factor in the corneal angiogenesis model. In endothelial cells, adenovirus-mediated overexpression of Gli3 promoted migration (modified Boyden chamber), small interfering RNA-mediated downregulation of Gli3 delayed tube formation (Matrigel), and Western analyses identified increases in Akt phosphorylation, extracellular signal-regulated kinase (ERK)1/2 activation, and c-Fos expression; however, promoter-reporter assays indicated that Gli3 overexpression does not modulate Gli-dependent transcription. Furthermore, the induction of endothelial cell migration by Gli3 was dependent on Akt and ERK1/2 activation.Collectively, these observations indicate that Gli3 contributes to vessel growth under both ischemic and nonischemic conditions and provide the first evidence that Gli3 regulates angiogenesis and endothelial cell activity in adult mammals.
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Project description:WNT signaling is critical in most aspects of skeletal development and homeostasis, and antagonists of WNT signaling are emergning as key regulatory proteins with great promise as therapeutic agents for bone disorders. Until recently Sost and its paralog Sostdc1 have been described as growth factors with highly restricted expression in the adult where Sost was assumed 'osteocyte-' and Sostdc1 'kidney-' specific. Here we show that these two proteins emerged throgh ancestral genome duplication and their expression patterns have diverged to span complimentary domains in most organ systems including musculoskeletal, cardiovascular, nervous, digestive, reproductive and respiratory. In the developing limb, Sost and Sostdc1 display dynamic expression patterns with Sost being restricted to the distal ectoderm and Sostdc1 to the proximal ectoderm and the mesenchyme. While Sostdc1-/- mice lack any obvious limb and skeletal defects, Sost-/- mice recapitulate the hand defects described for sclerosteosis patients. However, elevated WNT signaling in Sost-/-; Sostdc1-/- mice causes misregulation of SHH signaling, ectopic activation of Sox9 in the digit 1 field and ultimately preaxial polydactyly. In addition, we show that the syndactyly documented in Sclerosteosis is present in both Sost-/- and Sost-/-; Sostdc1-/- mice, and is driven by misregulation of Fgf8 in the AER, a region lacking Sost and Sostdc1 expression. This study highlights the complexity of WNT signaling in skeletal biology and disease and emphasizes how redundant mechanisms and non-cell autonomous effects can synergize to unveil new intricate phenotypes caused by elevated WNT signaling. Five arrays were analyzed, consisting of two total embryonic fore-limb RNA (experimental) and three total embryonic forelimb RNA (reference) samples at E11.5 DPC mouse (C57Bl6 strain). Embryos were not pooled to generate samples. Each time point has 3 to 5 biological replicates for limb bud samples, duplicates for whole embryos. Comparisons were made between limb bud samples and whole embryo at the same stage, fore-limb samples of different stages, hind-limb samples of different stages, and fore-limb samples compared to hind-limb samples at the same or the next stage.
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Project description:WNT signaling is critical in most aspects of skeletal development and homeostasis, and antagonists of WNT signaling are emergning as key regulatory proteins with great promise as therapeutic agents for bone disorders. Until recently Sost and its paralog Sostdc1 have been described as growth factors with highly restricted expression in the adult where Sost was assumed 'osteocyte-' and Sostdc1 'kidney-' specific. Here we show that these two proteins emerged throgh ancestral genome duplication and their expression patterns have diverged to span complimentary domains in most organ systems including musculoskeletal, cardiovascular, nervous, digestive, reproductive and respiratory. In the developing limb, Sost and Sostdc1 display dynamic expression patterns with Sost being restricted to the distal ectoderm and Sostdc1 to the proximal ectoderm and the mesenchyme. While Sostdc1-/- mice lack any obvious limb and skeletal defects, Sost-/- mice recapitulate the hand defects described for sclerosteosis patients. However, elevated WNT signaling in Sost-/-; Sostdc1-/- mice causes misregulation of SHH signaling, ectopic activation of Sox9 in the digit 1 field and ultimately preaxial polydactyly. In addition, we show that the syndactyly documented in Sclerosteosis is present in both Sost-/- and Sost-/-; Sostdc1-/- mice, and is driven by misregulation of Fgf8 in the AER, a region lacking Sost and Sostdc1 expression. This study highlights the complexity of WNT signaling in skeletal biology and disease and emphasizes how redundant mechanisms and non-cell autonomous effects can synergize to unveil new intricate phenotypes caused by elevated WNT signaling.
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