Project description:The morphogen and mitogen, Sonic Hedgehog, activates a Gli1-dependent transcription program that drives proliferation of granule neuron progenitors (GNPs) within the external germinal layer of the postnatally developing cerebellum. Medulloblastomas with mutations activating the Sonic Hedgehog signaling pathway preferentially arise within the external germinal layer, and the tumor cells closely resemble GNPs. Atoh1/Math1, a basic helix-loop-helix transcription factor essential for GNP histogenesis, does not induce medulloblastomas when expressed in primary mouse GNPs that are explanted from the early postnatal cerebellum and transplanted back into the brains of naïve mice. However, enforced expression of Atoh1 in primary GNPs enhances the oncogenicity of cells overexpressing Gli1 by almost three orders of magnitude. Unlike Gli1, Atoh1 cannot support GNP proliferation in the absence of Sonic Hedgehog signaling and does not govern expression of canonical cell cycle genes. Instead, Atoh1 maintains GNPs in a Sonic Hedgehog-responsive state by regulating genes that trigger neuronal differentiation, including many expressed in response to bone morphogenic protein-4. Therefore, by targeting multiple genes regulating the differentiation state of GNPs, Atoh1 collaborates with the pro-proliferative Gli1-dependent transcriptional program to influence medulloblastoma development. Keywords: disease state analysis 14 samples, 1 time series, 2 engineered Medulloblastoma tumors
Project description:Postnatal tissue quiescence is generally thought to be a default state in the absence of a proliferative stimulus such as injury. We now demonstrate that in the lung, quiescence in the adult is an actively maintained state and is regulated by paracrine hedgehog signaling. Epithelial-specific deletion of Sonic Hedgehog during normal homeostasis results in a proliferative expansion of the adjacent lung mesenchyme. Injury to the lung epithelium results in decreased hedgehog activation, accompanied by proliferative expansion of the adjacent mesenchyme. Moreover, reconstitution of Hedgehog signaling during epithelial injury attenuated the proliferative expansion of the adjacent mesenchyme. Hedgehog signaling maintains lung quiescence by attenuating PDGF signaling through blocking post-translational processing of PDGF receptor α/β into the mature isoforms. These results indicate that in postnatal tissues, epithelial cells can actively maintain mesenchymal quiescence via paracrine hedgehog activation, and that imbalances in this pathway could lead to aberrant mesenchymal expansion and postnatal disease. Fibroblasts were isolated from mouse lungs and grown in culture in triplicate wells. Samples were treated with vehicle or purmorphamine 5um for 24 hours and RNA was isolated for microarray.
Project description:The morphogen and mitogen, Sonic Hedgehog, activates a Gli1-dependent transcription program that drives proliferation of granule neuron progenitors (GNPs) within the external germinal layer of the postnatally developing cerebellum. Medulloblastomas with mutations activating the Sonic Hedgehog signaling pathway preferentially arise within the external germinal layer, and the tumor cells closely resemble GNPs. Atoh1/Math1, a basic helix-loop-helix transcription factor essential for GNP histogenesis, does not induce medulloblastomas when expressed in primary mouse GNPs that are explanted from the early postnatal cerebellum and transplanted back into the brains of naïve mice. However, enforced expression of Atoh1 in primary GNPs enhances the oncogenicity of cells overexpressing Gli1 by almost three orders of magnitude. Unlike Gli1, Atoh1 cannot support GNP proliferation in the absence of Sonic Hedgehog signaling and does not govern expression of canonical cell cycle genes. Instead, Atoh1 maintains GNPs in a Sonic Hedgehog-responsive state by regulating genes that trigger neuronal differentiation, including many expressed in response to bone morphogenic protein-4. Therefore, by targeting multiple genes regulating the differentiation state of GNPs, Atoh1 collaborates with the pro-proliferative Gli1-dependent transcriptional program to influence medulloblastoma development. Keywords: disease state analysis
Project description:The primary cilium is a signaling compartment that interprets Hedgehog signals through changes of its protein, lipid and second messenger compositions. Here, we combine proximity labeling of cilia with quantitative mass spectrometry to unbiasedly profile the time-dependent alterations of the ciliary proteome in response to Hedgehog. This approach correctly identifies the three factors known to undergo Hedgehog-regulated ciliary redistribution and reveals two such additional proteins. First, we find that a regulatory subunit of the cAMP-dependent protein kinase (PKA) rapidly exits cilia together with the G protein-coupled receptor GPR161 in response to Hedgehog; and we propose that the GPR161/PKA module senses and amplifies cAMP signals to modulate ciliary PKA activity. Second, we identify the phosphatase Paladin as a cell type-specific regulator of Hedgehog signaling that enters primary cilia upon pathway activation. The broad applicability of quantitative ciliary proteome profiling promises a rapid characterization of ciliopathies and their underlying signaling malfunctions.
Project description:The primary cilium is a signaling compartment that interprets Hedgehog signals through changes of its protein, lipid and second messenger compositions. Here, we combine proximity labeling of cilia with quantitative mass spectrometry to unbiasedly profile the time-dependent alterations of the ciliary proteome in response to Hedgehog. This approach correctly identifies the three factors known to undergo Hedgehog-regulated ciliary redistribution and reveals two such additional proteins. First, we find that a regulatory subunit of the cAMP-dependent protein kinase (PKA) rapidly exits cilia together with the G protein-coupled receptor GPR161 in response to Hedgehog; and we propose that the GPR161/PKA module senses and amplifies cAMP signals to modulate ciliary PKA activity. Second, we identify the phosphatase Paladin as a cell type-specific regulator of Hedgehog signaling that enters primary cilia upon pathway activation. The broad applicability of quantitative ciliary proteome profiling promises a rapid characterization of ciliopathies and their underlying signaling malfunctions.
Project description:The primary cilium is a signaling compartment that interprets Hedgehog signals through changes of its protein, lipid and second messenger compositions. Here, we combine proximity labeling of cilia with quantitative mass spectrometry to unbiasedly profile the time-dependent alterations of the ciliary proteome in response to Hedgehog. This approach correctly identifies the three factors known to undergo Hedgehog-regulated ciliary redistribution and reveals two such additional proteins. First, we find that a regulatory subunit of the cAMP-dependent protein kinase (PKA) rapidly exits cilia together with the G protein-coupled receptor GPR161 in response to Hedgehog; and we propose that the GPR161/PKA module senses and amplifies cAMP signals to modulate ciliary PKA activity. Second, we identify the phosphatase Paladin as a cell type-specific regulator of Hedgehog signaling that enters primary cilia upon pathway activation. The broad applicability of quantitative ciliary proteome profiling promises a rapid characterization of ciliopathies and their underlying signaling malfunctions.
Project description:Development of the cerebellum requires precise regulation of granule neuron progenitor (GNP) proliferation. Although it is known that primary cilia are necessary to support GNP proliferation, the exact molecular mechanism governing primary cilia dynamics within GNPs remains elusive. Here, we establish the pivotal roles for the centrosomal kinase TTBK2 (Tau tubulin kinase-2) and the E3 ubiquitin ligase HUWE1 in GNP proliferation. We show that TTBK2 is highly expressed in proliferating GNPs under Sonic Hedgehog (SHH) signaling, coinciding with active GNP proliferation and the presence of primary cilia. TTBK2 stabilizes primary cilia by inhibiting their disassembly, thereby promoting GNP proliferation in response to SHH. Mechanistically, we identify HUWE1 as a novel centrosomal E3 ligase that facilitates primary cilia disassembly by targeting TTBK2 degradation. Disassembly of primary cilia serves as a trigger for GNP differentiation, allowing their migration from the external granule layer (EGL) of the cerebellum to the internal granule layer (IGL) for subsequent maturation. Moreover, we have established a link between TTBK2 and SHH-type medulloblastoma (SHH-MB), a tumor characterized by uncontrolled GNP proliferation. TTBK2 depletion inhibits SHH-MB proliferation, indicating that TTBK2 may be a potential therapeutic target for this cancer type. In summary, our findings reveal the mechanism governing cerebellar development and highlight a potential anti-cancer strategy for SHH-MB.
Project description:Postnatal tissue quiescence is generally thought to be a default state in the absence of a proliferative stimulus such as injury. We now demonstrate that in the lung, quiescence in the adult is an actively maintained state and is regulated by paracrine hedgehog signaling. Epithelial-specific deletion of Sonic Hedgehog during normal homeostasis results in a proliferative expansion of the adjacent lung mesenchyme. Injury to the lung epithelium results in decreased hedgehog activation, accompanied by proliferative expansion of the adjacent mesenchyme. Moreover, reconstitution of Hedgehog signaling during epithelial injury attenuated the proliferative expansion of the adjacent mesenchyme. Hedgehog signaling maintains lung quiescence by attenuating PDGF signaling through blocking post-translational processing of PDGF receptor α/β into the mature isoforms. These results indicate that in postnatal tissues, epithelial cells can actively maintain mesenchymal quiescence via paracrine hedgehog activation, and that imbalances in this pathway could lead to aberrant mesenchymal expansion and postnatal disease.
Project description:Swiss-Webster B mouse postnatal day 4-5 primary cerebellar culture (pooled from litter mates) treated with sonic hedgehog (Shh), controls (veh), growth arrested (arrest), cycloheximide (cyc) for 1, 3 and 24 hours.
Project description:Aberrant Notch signaling has been linked to many cancers including choroid plexus (CP) tumors, a group of rare and predominantly pediatric brain neoplasms. We developed animal models of CP tumors by inducing sustained expression of Notch1 that recapitulate properties of human CP tumors with aberrant NOTCH signaling. Whole transcriptome and functional analyses showed that tumor cell proliferation is associated with Sonic Hedgehog (Shh) in the tumor microenvironment. Unlike CP epithelial cells, which have multiple primary cilia, tumor cells possess a solitary primary cilium as a result of Notch-mediated suppression of multiciliate diffferentiation. A Shh-driven signaling cascade in the primary cilium occurs in tumor cells but not in epithelial cells. Lineage studies show that CP tumors arise from mono-ciliated progenitors in the roof plate characterized by elevated Notch signaling. Abnormal SHH signaling and distinct ciliogenesis are detected in human CP tumors, suggesting SHH pathway and cilia differentiation as potential therapeutic avenues.