Role Of Hedgehog Signaling Research Articles

Role of hedgehog signaling in the pathogenesis and therapy of heterotopic ossification.

Heterotopic ossification (HO) is a pathological process that generates ectopic bone in soft tissues. Hedgehog signaling (Hh signaling) is a signaling pathway that plays an important role in embryonic development and involves three ligands: sonic hedgehog (Shh), Indian hedgehog (Ihh) and desert hedgehog (Dhh). Hh signaling also has an important role in skeletal development. This paper discusses the effects of Hh signaling on the process of HO formation and describes several signaling molecules that are involved in Hh-mediated processes: parathyroid Hormone-Related Protein (PTHrP) and Fkbp10 mediate the expression of Hh during chondrogenesic differentiation. Extracellular signal-regulated kinase (ERK), GNAs and Yes-Associated Protein (YAP) interact with Hh signaling to play a role in osteogenic differentiation. Runt-Related Transcription Factor 2 (Runx2), Mohawk gene (Mkx) and bone morphogenetic protein (BMP) mediate Hh signaling during both chondrogenic and osteogenic differentiation. This paper also discusses possible therapeutic options for HO, lists several Hh inhibitors and explores whether they could serve as emerging targets for the treatment of HO.

Characterization of a model of liver regeneration: Role of hedgehog signaling in experimental hepatic amoebiasis

The development of amoebic liver abscess (ALA) leads to liver necrosis, accompanied by an exacerbated inflammatory response and the formation of multiple granulomas. Adequate management of the infection through the administration of treatment and the timely response of the organ to the damage allows the injury to heal with optimal regeneration without leaving scar tissue, which does not occur in other types of damage such as viral hepatitis that may conducts to fibrosis or cirrhosis. The Hedgehog signaling pathway (Hh) is crucial in the embryonic stage, while in adults it is usually reactivated in response to acute or chronic injuries, regeneration, and wound healing. In this work, we characterized Hh in experimental hepatic amoebiasis model, with the administration of treatment with metronidazole, as well as a pathway inhibitor (cyclopamine), through histological and immunohistochemical analyses including an ultrastructure analysis through transmission electron microscopy. The results showed an increase in the percentage of lesions obtained, a decrease in the presence of newly formed hepatocytes, a generalized inflammatory response, irregular distribution of type I collagen accompanied by the presence of fibroblast-type cells and a decrease in effector cells of this pathway. These results constitute the first evidence of the association of the activation of Hh with the liver regeneration process in experimental amebiasis.

Hedgehog signaling mastery: R51211's promise in augmenting the therapeutic efficacy of sorafenib

Sorafenib is a multikinase inhibitor employed for managing hepatocellular carcinoma (HCC). The emergence of sorafenib resistance presents an obstacle to its therapeutic efficacy. One notable approach to overcoming sorafenib resistance is the exploration of combination therapies. The role of hedgehog signaling in sorafenib resistance has been also examined in HCC. R51211, known as itraconazole, has been safely employed in clinical practice. Through in vitro and in vivo investigations, we assessed the potential of R51211 to enhance the therapeutic efficacy of sorafenib by inhibiting the hedgehog signaling. The zero-interaction potency synergy model demonstrated a synergistic interaction between R51211 and sorafenib, a phenomenon reversed by the action of a smoothened receptor agonist. This dual therapy exhibited an increased capacity to induce apoptosis, as evidenced by alterations in the Bax/BCL-2 ratio and caspase-3, along with a propensity to promote autophagy, as indicated by changes in BECN1, p62, and the LC3I/LC3II ratio. Furthermore, the combination therapy resulted in significant reductions in biomarkers associated with liver preneoplastic alterations, improved liver microstructure, and mitigated changes in liver function enzymes. The substantial decrease in hedgehog components (Shh, SMO, GLI1, and GLI2) following R51211 treatment appears to be a key factor contributing to the increased efficacy of sorafenib. In conclusion, our study highlights the potential of R51211 as an adjunct to sorafenib, introducing a new dimension to this combination therapy through the modulation of the hedgehog signaling pathway. Further investigations are essential to validate the therapeutic efficacy of this combined approach in inhibiting the development of liver cancer.

Abstract B035: Investigating the roles of GLI transcription factors in the pancreatic cancer microenvironment

Abstract Pancreatic ductal adenocarcinoma (PDA) remains a difficult cancer to treat due to an extensive and complex tumor microenvironment. In particular, intercellular signaling between tumor cells, fibroblasts and immune cells is a key contributor to pancreatic tumor growth. One of these signals, the Hedgehog (HH) pathway, is a known feature of PDA. Pancreatic tumor cells secrete HH ligands, which signal in a paracrine fashion to fibroblasts in the tumor microenvironment. Notably, the role of HH signaling is complicated, with reports suggesting both tumor-promoting and tumor-restraining functions in pancreatic cancer. GLI proteins (GLI1-3) are the transcriptional effectors of the HH pathway; their contribution to pancreatic tumor growth is equally complex. This study seeks to investigate the contribution of GLI1-3 in PDA progression. Our lab has demonstrated that Gli1-3 are expressed in pancreatic fibroblasts and that all three Glis functionally contribute to pancreatic cancer progression through effects on immune cell infiltration. To further explore the mechanisms of GLI function, we have generated a novel mouse model carrying endogenous, epitope-tagged Gli alleles (Gli1FLAG/FLAG;Gli2HA/HA;Gli3V5/V5). This model will allow us to define GLI protein processing and localization as well as the identification of target genes to elucidate the contribution of GLI-driven transcriptional programs that regulate tumor immune infiltration in PDA. Citation Format: Paola Isabel Medina-Cabrera, Michael Scales, Nina Steele, Benjamin Allen, Marina Pasca di Magliano. Investigating the roles of GLI transcription factors in the pancreatic cancer microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B035.

The Role of Hedgehog Signaling in the Melanoma Tumor Bone Microenvironment.

A crucial regulator in melanoma progression and treatment resistance is tumor microenvironments, and Hedgehog (Hh) signals activated in a tumor bone microenvironment are a potential new therapeutic target. The mechanism of bone destruction by melanomas involving Hh/Gli signaling in such a tumor microenvironment is unknown. Here, we analyzed surgically resected oral malignant melanoma specimens and observed that Sonic Hedgehog, Gli1, and Gli2 were highly expressed in tumor cells, vasculatures, and osteoclasts. We established a tumor bone destruction mouse model by inoculating B16 cells into the bone marrow space of the right tibial metaphysis of 5-week-old female C57BL mice. An intraperitoneal administration of GANT61 (40 mg/kg), a small-molecule inhibitor of Gli1 and Gli2, resulted in significant inhibition of cortical bone destruction, TRAP-positive osteoclasts within the cortical bone, and endomucin-positive tumor vessels. The gene set enrichment analysis suggested that genes involved in apoptosis, angiogenesis, and the PD-L1 expression pathway in cancer were significantly altered by the GANT61 treatment. A flow cytometry analysis revealed that PD-L1 expression was significantly decreased in cells in which late apoptosis was induced by the GANT61 treatment. These results suggest that molecular targeting of Gli1 and Gli2 may release immunosuppression of the tumor bone microenvironment through normalization of abnormal angiogenesis and bone remodeling in advanced melanoma with jaw bone invasion.

PiRNAs regulate a Hedgehog germline-to-soma pro-aging signal

The reproductive system regulates somatic aging through competing anti- and pro-aging signals. Germline removal extends somatic lifespan through conserved pathways including insulin and mammalian target-of-rapamycin signaling, while germline hyperactivity shortens lifespan through unknown mechanisms. Here we show that mating-induced germline hyperactivity downregulates piRNAs, in turn desilencing their targets, including the Hedgehog-like ligand-encoding genes wrt-1 and wrt-10, ultimately causing somatic collapse and death. Germline-produced Hedgehog signals require PTR-6 and PTR-16 receptors for mating-induced shrinking and death. Our results reveal an unconventional role of the piRNA pathway in transcriptional regulation of Hedgehog signaling and a new role of Hedgehog signaling in the regulation of longevity and somatic maintenance: Hedgehog signaling is controlled by the tunable piRNA pathway to encode the previously unknown germline-to-soma pro-aging signal. Mating-induced piRNA downregulation in the germline and subsequent Hedgehog signaling to the soma enable the animal to tune somatic resource allocation to germline needs, optimizing reproductive timing and survival.

Combined Inhibition of Smoothened and the DNA Damage Checkpoint WEE1 Exerts Antitumor Activity in Cholangiocarcinoma.

Cholangiocarcinoma (CCA) is characterized by resistance to chemotherapy and a poor prognosis. Therefore, treatments that can effectively suppress tumor growth are urgently needed. Aberrant activation of hedgehog (HH) signaling has been implicated in several cancers, including those of the hepatobiliary tract. However, the role of HH signaling in intrahepatic CCA (iCCA) has not been completely elucidated. In this study, we addressed the function of the main transducer Smoothened (SMO) and the transcription factors (TFs) GLI1 and GLI2 in iCCA. In addition, we evaluated the potential benefits of the combined inhibition of SMO and the DNA damage kinase WEE1. Transcriptomic analysis of 152 human iCCA samples showed increased expression of GLI1, GLI2, and Patched 1 (PTCH1) in tumor tissues compared with nontumor tissues. Genetic silencing of SMO, GLI1, and GLI2 inhibited the growth, survival, invasiveness, and self-renewal of iCCA cells. Pharmacologic inhibition of SMO reduced iCCA growth and viability in vitro, by inducing double-strand break DNA damage, leading to mitotic arrest and apoptotic cell death. Importantly, SMO inhibition resulted in the activation of the G2-M checkpoint and DNA damage kinase WEE1, increasing the vulnerability to WEE1 inhibition. Hence, the combination of MRT-92 with the WEE1 inhibitor AZD-1775 showed increased antitumor activity in vitro and in iCCA xenografts compared with single treatments. These data indicate that combined inhibition of SMO and WEE1 reduces tumor burden and may represent a strategy for the clinical development of novel therapeutic approaches in iCCA.

Ihog proteins contribute to integrin-mediated focal adhesions.

Integrin expression forms focal adhesions, but how this process is physiologically regulated is unclear. Ihog proteins are evolutionarily conserved, playing roles in Hedgehog signaling and serving as trans-homophilic adhesion molecules to mediate cell-cell interactions. Whether these proteins are also engaged in other cell adhesion processes remains unknown. Here, we report that Drosophila Ihog proteins function in the integrin-mediated adhesions. Removal of Ihog proteins causes blister and spheroidal muscle in wings and embryos, respectively. We demonstrate that Ihog proteins interact with integrin via the extracellular portion and that their removal perturbs integrin distribution. Finally, we show that Boc, a mammalian Ihog protein, rescues the embryonic defects caused by removing its Drosophila homologs. We thus propose that Ihog proteins contribute to integrin-mediated focal adhesions.

Hedgehog/GLI signaling in hematopoietic development and acute myeloid leukemia-From bench to bedside.

While the underlying genetic alterations and biology of acute myeloid leukemia (AML), an aggressive hematologic malignancy characterized by clonal expansion of undifferentiated myeloid cells, have been gradually unraveled in the last decades, translation into clinical treatment approaches has only just begun. High relapse rates remain a major challenge in AML therapy and are to a large extent attributed to the persistence of treatment-resistant leukemic stem cells (LSCs). The Hedgehog (HH) signaling pathway is crucial for the development and progression of multiple cancer stem cell driven tumors, including AML, and has therefore gained interest as a therapeutic target. In this review, we give an overview of the major components of the HH signaling pathway, dissect HH functions in normal and malignant hematopoiesis, and specifically elaborate on the role of HH signaling in AML pathogenesis and resistance. Furthermore, we summarize preclinical and clinical HH inhibitor studies, leading to the approval of the HH pathway inhibitor glasdegib, in combination with low-dose cytarabine, for AML treatment.

PTCH1 and AXIN2 modulation of AR copy number effects on AR gene overexpression in metastatic castration resistant prostate cancer (mCRPC).

e17026 Background: Androgen receptor (AR) signaling is a critical pathway in prostate cancer progression. Reactivation of the AR pathway is a key driver in mCRPC. Patients with mCRPC often develop resistance to novel AR signaling inhibitors (ARSIs) such as enzalutamide. AR inhibitor resistance leads to shorter overall and progression-free survival and can be attributed to AR gene amplification with subsequent AR overexpression and androgen-sensitization in prostate tumors. Identifying novel modulators of AR amplification in patients progressing on ARSIs may lead towards potential targets in drug discovery. Methods: In this cross-sectional study, an in silico patient model was developed on prescribed drug therapies and failed therapies patient information, PSA measures, ̃100 mutation variables including somatic, germline, and gain/loss mutations, and ̃1K gene expressions data from 275 mCRPC patients obtained from the Tempus database using GNS Healthcare’s Causal artificial intelligence technology, REFS. A causal network model was reconstructed based on patient data with inferred effect estimates. The network model was topologically surveyed for biological interactions. Results: Causal analysis of this model uncovered two germline mutations, located in PTCH1 and AXIN2, which modify the effect of AR copy number gain ( ARgain+ : copy number 6, ARgain- : copy number < 6) on AR gene expression. For PTCH1-mutant group, there was a 2-fold increase in AR gene expression in ARgain+ patients compared to ARgain- patients (p = 2.1e-12), while only 1.4 fold increase in AR gene expression from the PTCH1 non-mutant group (p = 6.3e-08). Similarly, there was a 2-fold increase in AR gene expression in ARgain+ patients compared to ARgain- patients (p = 7.2e-16) for the AXIN2-mutant group, while only one-fold increase in AR gene expression with the AXIN2 non-mutant group (p = 0.001). The C to T missense mutation in codon 3746 in PTCH1 and codon 148 in AXIN2 have higher prevalences, 55% and 72%, respectively in this mCRPC cohort compared to their population allele frequencies, 38% and 47%, respectively. Conclusions: PTCH1 and AXIN2 mutations from our analyses is consistent with a literature reported role for Hedgehog signaling and Wnt/-catenin signaling pathways, respectively, influencing the disease progression in castration-resistant prostate cancer. Our findings suggest that the missense germline mutations in PTCH1 and AXIN2 predicts response to enzalutamide and other ARSIs in CRPC setting, and propose potential targets for combination therapy to overcome ARSI drug resistance in hormone-refractory prostate cancer. [Table: see text]

An essential function for autocrine hedgehog signaling in epithelial proliferation and differentiation in the trachea.

ABSTRACTThe tracheal epithelium is a primary target for pulmonary diseases as it provides a conduit for air flow between the environment and the lung lobes. The cellular and molecular mechanisms underlying airway epithelial cell proliferation and differentiation remain poorly understood. Hedgehog (HH) signaling orchestrates communication between epithelial and mesenchymal cells in the lung, where it modulates stromal cell proliferation, differentiation and signaling back to the epithelium. Here, we reveal a previously unreported autocrine function of HH signaling in airway epithelial cells. Epithelial cell depletion of the ligand sonic hedgehog (SHH) or its effector smoothened (SMO) causes defects in both epithelial cell proliferation and differentiation. In cultured primary human airway epithelial cells, HH signaling inhibition also hampers cell proliferation and differentiation. Epithelial HH function is mediated, at least in part, through transcriptional activation, as HH signaling inhibition leads to downregulation of cell type-specific transcription factor genes in both the mouse trachea and human airway epithelial cells. These results provide new insights into the role of HH signaling in epithelial cell proliferation and differentiation during airway development.

2021 Canadian Surgery Forum: Virtual, online Sept. 21-24, 2021.

# 01. Design and validation of a unique endoscopy simulator using a commercial video game {#article-title-2} Procedural simulation has been shown to enhance early endoscopy training. In this proof of concept study, we aimed to show that a first-person shooter (FPS) video game with a novel in-house

Abstract PR-014: Hedgehog represses angiogenesis in PDAC through a paracrine cascade mediated by Wif1

Abstract Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an extremely heterogeneous tumor microenvironment (TME) paired with a sparse and compromised vascular network. These features of the TME shape drug responses and contributes to PDAC’s distinctive chemotherapeutic resistance. Prior work demonstrated that inhibition of the Hedgehog (Hh) signaling using Smoothened (Smo) inhibitors relieved some of the local angiogenic suppression. However, the precise mechanisms through which the Hh pathway regulates angiogenesis has remained elusive. Subsequent studies evaluating different timepoints yielded conflicting data on the role of Hedgehog signaling in angiogenesis. In order to replicate the heterogeneity and spatial patterning of cells in pancreatic tumors, we developed a novel tumor explant system for short-term cultures of both murine and human PDAC. Briefly, we cultured intact 300 μm slices of PDAC tissues in a modified gelatin platform system with a novel culture medium informed by the metabolic composition of PDAC tumor interstitial fluid. This system replicates some of the nutrient/waste gradient of PDAC and enables tumors to be culture up to one week with good representation of multiple cell types. Studies in explants were complemented by work in the KPC genetically engineered model of PDAC. Comparison of short versus long-term Smo inhibition in KPC mouse pancreatic tumors revealed a robust increase in vessel density in short-term treatment, which is lost at later timepoints. Studies in murine and human PDAC explants employing different Smo inhibitors demonstrated increased endothelial tip cell formation upon two days of treatment, resulting in increased vessel density after four days. Computational analyses of human PDAC single cell RNAseq data identified candidate cellular subsets potentially involved in the signaling cascade. RNAseq of pre- and on-treatment tumor samples from KPC mice identified Wif1 as a candidate Hh target gene that effected these programs. Mechanistic studies in tumor explants reveal a complex, multi-step mechanism involving multiple cell types that led to suppression of angiogenesis in PDAC. These studies demonstrate how the tumor explant platform can elucidate complex intercellular signaling cascades and provide a candidate mechanism for the Hh-mediated suppression of angiogenesis in PDAC. Citation Format: Marie C. Hasselluhn, Amanda R. Decker, Alvaro Curiel Garcia, Carlo Maurer, Dafydd Thomas, Kenneth P. Olive. Hedgehog represses angiogenesis in PDAC through a paracrine cascade mediated by Wif1 [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PR-014.

The Hedgehog Signaling Pathway is Expressed in the Adult Mouse Hypothalamus and Modulated by Fasting.

The hedgehog signaling pathway is best known for its role in developmental patterning of the neural tube and limb bud. More recently, hedgehog signaling has been recognized for its roles in growth of adult tissues and maintenance of progenitor cell niches. However, the role of hedgehog signaling in fully differentiated cells like neurons in the adult brain is less clear. In mammals, coordination of hedgehog pathway activity relies on primary cilia and patients with ciliopathies such as Bardet–Biedl and Alström syndrome exhibit clinical features clearly attributable to errant hedgehog such as polydactyly. However, these ciliopathies also present with features not clearly associated with hedgehog signaling such as hyperphagia-associated obesity. How hedgehog signaling may contribute to feeding behavior is complex and unclear, but cilia are critical for proper energy homeostasis. Here, we provide a detailed analysis of the expression of core components of the hedgehog signaling pathway in the adult mouse hypothalamus with an emphasis on feeding centers. We show that hedgehog pathway genes continue to be expressed in differentiated neurons important for the regulation of feeding behavior. Furthermore, we demonstrate for the first time that pathway activity is regulated at the transcriptional level by fasting. These data suggest that hedgehog signaling is involved in the proper functioning of brain regions that regulate feeding behavior and that hedgehog pathway dysfunction may play a role in the obesity observed in certain ciliopathies.

Sequences in the stalk domain regulate auto-inhibition and ciliary tip localization of the immotile kinesin-4 KIF7.

The kinesin-4 member KIF7 plays critical roles in Hedgehog signaling in vertebrate cells. KIF7 is an atypical kinesin as it binds to microtubules but is immotile. We demonstrate that, like conventional kinesins, KIF7 is regulated by auto-inhibition, as the full-length protein is inactive for microtubule binding in cells. We identify a segment, the inhibitory coiled coil (inhCC), that is required for auto-inhibition of KIF7, whereas the adjacent regulatory coiled coil (rCC) that contributes to auto-inhibition of the motile kinesin-4s KIF21A and KIF21B is not sufficient for KIF7 auto-inhibition. Disease-associated mutations in the inhCC relieve auto-inhibition and result in strong microtubule binding. Surprisingly, uninhibited KIF7 proteins did not bind preferentially to or track the plus ends of growing microtubules in cells, as suggested by previous in vitro work, but rather bound along cytosolic and axonemal microtubules. Localization to the tip of the primary cilium also required the inhCC, and could be increased by disease-associated mutations regardless of the auto-inhibition state of the protein. These findings suggest that loss of KIF7 auto-inhibition and/or altered cilium tip localization can contribute to the pathogenesis of human disease.

Plasticity and genetic basis of cichlid gill arch anatomy reveal novel roles for Hedgehog signaling.

Teleost gill arches are exquisitely evolved to maximize foraging efficiency, and include structures for the capture, filtering, and processing of prey. While both plasticity and a genetic basis for gill arch traits have been noted, the relative contributions of genetics and the environment in shaping these structures remains poorly understood. East African cichlids are particularly useful in this line of study due to their highly diverse and plastic feeding apparatus. Here we explore the gene-by-environmental effects on cichlid GRs by rearing pure bred species and their F3 hybrids in different foraging environments. We find that anatomical differences between species are dependent on the environment. The genetic architecture of these traits is also largely distinct between foraging environments. We did, however, note a few genomic "hotspots" where multiple traits map to a common region. One of these, for GR number across multiple arches, maps to the ptch1 locus, a key component of the Hedgehog (Hh) pathway that has previously been implicated in cichlid oral jaw shape and plasticity. Since Hh signalling has not previously been implicated in GR development, we explored functional roles for this pathway. Using a small molecule inhibitor in cichlids, as well as zebrafish transgenic systems, we demonstrate that Hh levels negatively regulate GR number, and are both necessary and sufficient to maintain plasticity in this trait. In all these data underscore the critical importance of the environment in determining the relationship between genotype and phenotype, and provide a molecular inroad to better understand the origins of variation in this important foraging-related trait.

Hedging against Neuropathic Pain: Role of Hedgehog Signaling in Pathological Nerve Healing.

The peripheral nervous system has important regenerative capacities that regulate and restore peripheral nerve homeostasis. Following peripheral nerve injury, the nerve undergoes a highly regulated degeneration and regeneration process called Wallerian degeneration, where numerous cell populations interact to allow proper nerve healing. Recent studies have evidenced the prominent role of morphogenetic Hedgehog signaling pathway and its main effectors, Sonic Hedgehog (SHH) and Desert Hedgehog (DHH) in the regenerative drive following nerve injury. Furthermore, dysfunctional regeneration and/or dysfunctional Hedgehog signaling participate in the development of chronic neuropathic pain that sometimes accompanies nerve healing in the clinical context. Understanding the implications of this key signaling pathway could provide exciting new perspectives for future research on peripheral nerve healing.

Distinct Cation Gradients Power Cholesterol Transport at Different Key Points in the Hedgehog Signaling Pathway.

Cholesterol plays two critical roles in Hedgehog signaling, a fundamental pathway in animal development and cancer: it covalently modifies the Sonic hedgehog (SHH) ligand, restricting its release from producing cells, and directly activates Smoothened in responding cells. In both contexts, a membrane protein related to bacterial RND transporters regulates cholesterol: Dispatched1 controls release of cholesterylated SHH, and Patched1 antagonizes Smoothened activation by cholesterol. The mechanism and driving force for eukaryotic RND proteins, including Dispatched1 and Patched1, are unknown. Here, we show that Dispatched1 acts enzymatically to catalyze SHH release. Dispatched1 uses the energy of the plasma membrane Na+ gradient, thus functioning as an SHH/Na+ antiporter. In contrast, Patched1 repression of Smoothened requires the opposing K+ gradient. Our results clarify the transporter activity of essential eukaryotic RND proteins and demonstrate that the two main cation gradients of animal cells differentially power cholesterol transport at two crucial steps in the Hedgehog pathway.

Hedgehog signaling regulates the basement membrane remodeling during folliculogenesis in the neonatal mouse ovary.

In the mouse ovary, interactions between oocytes and somatic cells are essential for folliculogenesis and subsequent follicle development. The polyovular follicle (PF), which contains more than two oocytes in a follicle, can be induced in the neonatal mouse ovary when interactions between oocytes and somatic cells are disrupted by agents such as the potent synthetic estrogen diethylstilbestrol (DES) acting through estrogen receptor (ER) β. Hedgehog signaling is known to regulate granulosa cell proliferation, thecal cell differentiation, and follicle growth. To investigate the role of hedgehog signaling in the early folliculogenesis and in PF induction by DES, neonatal mouse ovaries were cultured with or without 10 μM cyclopamine (CPA), an inhibitor of hedgehog signaling, and grafted under the kidney capsule of adult ovariectomized host mice. The number and the incidence of PFs were significantly increased in organ-cultured ovaries post-grafting. Expression of procollagen type IV, alpha 1 (Col4a1) in organ-cultured ovaries was significantly reduced by CPA, but not by DES. The expression of two hedgehog ligands, Desert hedgehog (Dhh) and Indian hedgehog (Ihh), and a target gene, Hedgehog interacting protein (Hhip), was significantly increased by DES both in WT and ERβ KO mice. Therefore, we infer that DES can affect expression of those genes through ERα but not via suppression of hedgehog signaling. Thus, PFs are induced by DES or CPA, but the induction mechanism is different. Our results revealed an important role of hedgehog signaling in basement membrane remodeling during folliculogenesis even before thecal cell differentiation.

Hedgehog Signaling Regulates Epithelial Morphogenesis to Position the Ventral Embryonic Midline.

Despite much progress toward understanding how epithelial morphogenesis is shaped by intra-epithelial processes including contractility, polarity, and adhesion, much less is known regarding how such cellular processes are coordinated by extra-epithelial signaling. During embryogenesis, the coelomic epithelia on the two sides of the chick embryo undergo symmetrical lengthening and thinning, converging medially to generate and position the dorsal mesentery (DM) in the embryonic midline. We find that Hedgehog signaling, acting through downstream effectors Sec5 (ExoC2), an exocyst complex component, and RhoU (Wrch-1), a small GTPase, regulates coelomic epithelium morphogenesis to guide DM midline positioning. These effects are accompanied by changes in epithelial cell-cell alignment and N-cadherin and laminin distribution, suggesting Hedgehog regulation of cell organization within the coelomic epithelium. These results indicate a role for Hedgehog signaling in regulating epithelial morphology and provide an example of how transcellular signaling can modulate specific cellular processes to shape tissue morphogenesis.