Project description:Aberrant sonic hedeghog signaling is implicated in the development of various cancer entities such as medulloblastoma. The canonical signaling cascade has been studied for years. Activation of GLI transcription factors was revealed as the driving force upon pathway activation. Phosphorylation by Proteinkinase A, Casein Kinase 1 and Glycogen Synthase Kinase 3 β has been found to influence the degradation of the GLI transcription factors. However, the deeper role of phosphorylation in the signal transduction remains unclear. We, therefore, applied comprehensive HPLC-MS/MS based phosphoproteomics to reveal phosphorylation dynamics underlying the chemical activation and inhibition of sonic hedgehog signaling in human medulloblastoma cells. Human medulloblastoma cells were treated with SAG (Hh pathway induction) and Vismodegib (Hh pathway inhibition) for 5 and 15 minutes. Our phosphoproteomic profiling revealed a central role of phosphorylation in the regulation of ciliary assembly, trafficking and signal transduction after 5 minutes treatment. ERK/MAPK signaling besides protein kinase A signaling and mTOR signaling were differentially regulated. Activation of Polo-like kinase 1 and inhibtion of Caseinkinase 2A1 was characteristic for Vismodegib treatment while SAG treatment induced Aurora kinase A activity. Distinctive phosphorylation of central players of sonic Hh signaling such as Smoothened, SUFU, Gli2 and Gli3 was obtained after 15 minutes treatment.
Project description:Paracrine Hedgehog (Hh) signaling regulates growth and patterning in many Drosophila organs. We mapped chromatin binding sites for Cubitus interruptus (Ci), the transcription factor that mediates outputs of Hh signal transduction, and we analyzed transcription profiles of control and mutant embryos to identify genes that are regulated by Hh. Putative targets we identified include several Hh pathway components, most previously identified targets, and many targets that are novel. Analysis of expression patterns of pathway components and target genes gave evidence of autocrine Hh signaling in the optic primordium of the embryo. And, every Hh target we analyzed that is not a pathway component appeared to be regulated by Hh in a tissue-specific manner. We present evidence that Hh-dependent tissue specificity is dependent upon transcription factors that are Hh-independent, suggesting that “pre-patterns” of transcription factors partner with Ci to make Hh-dependent gene expression position-specific.
Project description:Paracrine Hedgehog (Hh) signaling regulates growth and patterning in many Drosophila organs. We mapped chromatin binding sites for Cubitus interruptus (Ci), the transcription factor that mediates outputs of Hh signal transduction, and we analyzed transcription profiles of control and mutant embryos to identify genes that are regulated by Hh. Putative targets we identified include several Hh pathway components, most previously identified targets, and many targets that are novel. Analysis of expression patterns of pathway components and target genes gave evidence of autocrine Hh signaling in the optic primordium of the embryo. And, every Hh target we analyzed that is not a pathway component appeared to be regulated by Hh in a tissue-specific manner. We present evidence that Hh-dependent tissue specificity is dependent upon transcription factors that are Hh-independent, suggesting that “pre-patterns” of transcription factors partner with Ci to make Hh-dependent gene expression position-specific. Analysis of the expression profiles of loss of function mutantations in core components of the Hh signaling pathway. A total of 14 samples were analysed consisting of comparisons of hh-, ci-, smo-, ptc-, and Cim1-m4 (Activator) mis-expression embryos compared to wt sibling embryos.
Project description:Purpose: Most Hedgehog responsive gene expression is mediated through GLI de-repression. Additionally GLI -repression is proposed to play roles in limb pre-patterning before HH pathway activation. This study evaluates if GLI repression is established prior to HH pathway activation. Methods: To determine if GLI-repression is established prior to pathway activation, we used genomic approaches to study GLI-mediated repression using the mouse developing limb as a model. We identified pre-HH (E9.25, 21-23S) and post-HH (E10.5, 32-25S) GLI3 binding regions using CUT&RUN for endogenous FLAG-tagged GLI3 proteins. Using a combination of ChIP-seq, CUT&RUN, CUT&Tag, ATAC-seq and RNA-seq, we tested whether loss of Gli3 prior to HH signaling was able to de-repress genes and enhancers, as it does after HH signaling. Results: Prior to HH signaling, GLI3 binds to poised, accessible regions with histone deacetylase (HDAC) proteins, similar to post-HH signaling. Despite GLI3 binding to most regions as it does in the post-HH limb, loss of Gli3 is unable to prematurely active target genes or enhancers. Furthermore, we find that GLI3-dependent chromatin compaction does not occur until roughly 10 hours after HH signaling would have normally been induced. Collectively, these results support that GLI repressor proteins are inert prior to HH pathway activation.
Project description:Mesenchymal-epithelial interactions play a critical role in organ development, stem cells and disease. During intestinal development, pseudostratified epithelia undergo dramatic morphogenesis called villification, to form finger-like projections, in which mesenchymal cell clustering and muscle layers play a key role. In the adult, the gut mesenchyme is proposed as a key intestinal stem cell niche providing essential niche signals such as Wnt ligands, while the TGF beta signaling mediated gut stromal program is critical for cancer progression. However, how these signals are produced is currently unknown. In the gut, Hedgehog (Hh) signaling acts strictly in a paracrine manner: Hh ligands are expressed in the epithelium and activate signaling exclusively in the mesenchyme. Notably, Hh signaling is not only essential for mesenchymal clustering and muscle differentiation, it is also involved in intestinal tumorigenesis. To investigate Hh mediated mechanisms, we analyzed mice deleted for key Hh negative regulators, Sufu and/or Spop in the gut mesenchyme, and demonstrated their dosage dependent role in the negative regulation of Hh signaling. Although these mutants exhibit abnormal mesenchymal cell growth and functionally defective muscle layers, villification is completed with proper mesenchymal clustering, implying a permissive role for Hh signaling. These mesenchymal defects are partially rescued by Gli2 reduction, demonstrating the significance of its transcriptional regulation. Surprisingly, in contrast to its known inhibitory role in epithelial proliferation, abnormal Hh activation in the gut mesenchyme leads to increased epithelial proliferation. Corroborating this data, Sufu reduction is sufficient to promote intestinal tumorigenesis, while Gli2 heterozygosity suppresses it. To define GLI2-mediated downstream mechanisms, we mapped its binding sites and analyzed gene expression genome-wide, identifying one of the most robust Hh direct targetome data sets ever reported. This work reveals the GLI2 transcriptional regulation of Wnt and TGF beta pathways in stem cell proliferation and muscle differentiation, providing mechanistic insight into the intestinal stem cell niche in development and tumorigenesis.
Project description:This experiment was specifically designed to measure neural targets of Shh signaling, we sought to profile the genes upregulated by Hh signaling in the ventral neural tube to obtain a valid dataset. To obtain ventral-specific markers, we generated retinoic acid-treated EBs grown in the presence or absence of HH-Ag. We did not observe induction of ventral Hh markers in RA-treated constitutive Gli1FLAG EBs and used these for the control, baseline set. The presence of FoxA2, Nkx2.9 and Nkx6.1 amongst the top 10 genes based on expression levels suggests that profiling significantly enriches for Hh-dependent cell types. As expected, the benchmark standard Gli1 was not up-regulated in our array, since it is constitutively expressed in the control as well. Keywords: neural progenitors, embryoid bodies, differentiation, Hedgehog, retinoic acid
Project description:Global warming and rising temperature significantly increase the incidence of heat stress, which is known to affect the process of inflammation and aging. However, the effect of heat stress on skin melanogenesis is not fully known. We found that healthy foreskin tissues underwent significant pigmentation when exposed to 41℃. Furthermore, heat stress promoted melanogenesis in pigment cells by increasing the paracrine effects of keratinocytes. High-throughput RNA sequencing showed that heat stress activates the Hedgehog (Hh) signaling pathway in keratinocytes. The agonists of Hh signaling promote the paracrine effect of keratinocytes on melanogenesis. In addition, TRPV3 agonists activate the Hh signaling in keratinocytes and augment its paracrine effect on melanogenesis. The heat-induced activation of Hh signaling is dependent on TRPV3-mediated Ca2+ influx. Heat exposure promotes melanogenesis by increasing the paracrine effects in keratinocytes via the TRPV3/Ca2+/Hh signaling pathway. Our findings provide insights into the mechanisms of heat-induced skin pigmentation.