TGF-β1/SMAD3-driven GLI2 isoform expression contributes to aggressive phenotypes of hepatocellular carcinoma

Hedgehog signaling is activated in response to liver injury, and modulates organogenesis. However, the role of non-canonical hedgehog activation via TGF-β1/SMAD3 in hepatic carcinogenesis is poorly understood. TGF-β1/SMAD3-mediated non-canonical activation was found in approximately half of GLI2-positive hepatocellular carcinoma (HCC), and two new GLI2 isoforms with transactivating activity were identified. Phospho-SMAD3 interacted with active GLI2 isoforms to transactivate downstream genes in modulation of stemness, epithelial-mesenchymal transition, chemo-resistance and metastasis in poorly-differentiated hepatoma cells. Non-canonical activation of hedgehog signaling was confirmed in a transgenic HBV-associated HCC mouse model. Inhibition of TGF-β/SMAD3 signaling reduced lung metastasis in a mouse in situ hepatic xenograft model. In another cohort of 55 HCC patients, subjects with high GLI2 expression had a shorter disease-free survival than those with low expression. Moreover, co-positivity of GLI2 with SMAD3 was observed in 87.5% of relapsed HCC patients with high GLI2 expression, indicating an increased risk of post-resection recurrence of HCC. The findings underscore that suppressing the non-canonical hedgehog signaling pathway may confer a potential strategy in the treatment of HCC.

Ptch1 is essential for cochlear marginal cell differentiation and stria vascularis formation

A common cause of deafness in humans is dysregulation of the endocochlear potential generated by the stria vascularis (SV). Thus, proper formation of the SV is critical for hearing. Using single-cell transcriptomics and a series of Shh signaling mutants, we discovered that the Shh receptor Patched1 (Ptch1) is essential for marginal cell (MC) differentiation and SV formation. Single-cell RNA sequencing analyses revealed that the cochlear roof epithelium is already specified into discrete domains with distinctive gene expression profiles at embryonic day 14, with Gsc as a marker gene of the MC lineage. Ptch1 deficiency leads to defective specification of MC precursors along the cochlear basal-apical regions. We demonstrated that elevated Gli2 levels impede MC differentiation through sustaining Otx2 expression and maintaining the progenitor state of MC precursors. Our results uncover an early specification of cochlear non-sensory epithelial cells and establish a crucial role of the Ptch1-Gli2 axis in regulating the development of SV.

Heterozygous missense variant in GLI2 impairs human endocrine pancreas development

Missense variants are the most common type of coding genetic variants. Their functional assessment is fundamental for defining any implication in human diseases and may also uncover genes that are essential for human organ development. Here, we apply CRISPR-Cas9 gene editing on human iPSCs to study a heterozygous missense variant in GLI2 identified in two siblings with early-onset and insulin-dependent diabetes of unknown cause. GLI2 is a primary mediator of the Hedgehog pathway, which regulates pancreatic β-cell development in mice. However, neither mutations in GLI2 nor Hedgehog dysregulation have been reported as cause or predisposition to diabetes. We establish and study a set of isogenic iPSC lines harbouring the missense variant for their ability to differentiate into pancreatic β-like cells. Interestingly, iPSCs carrying the missense variant show altered GLI2 transcriptional activity and impaired differentiation of pancreatic progenitors into endocrine cells. RNASeq and network analyses unveil a crosstalk between Hedgehog and WNT pathways, with the dysregulation of non-canonical WNT signaling in pancreatic progenitors carrying the GLI2 missense variant. Collectively, our findings underscore an essential role for GLI2 in human endocrine development and identify a gene variant that may lead to diabetes.

Anoikis regulator GLI2 promotes NC cell immunity escape by TGF-β-mediated non-classic hedgehog signaling in colorectal cancer: based on artificial intelligence and big data analysis

BACKGROUND

Anoikis is a speed-limited procedure to inhibit tumor metastasis during epithelial-mesenchymal transition (EMT). Previous studies have explored anoikis-related genes (ARG) in predicting prognosis and distinguishing tumoral immunity in many types of cancer. However, the role of ARGs in regulating NK cell exhaustion (NKE) and in predicting chemotherapy sensitivity is not clear. Therefore, it is necessary to work on it.

METHODS

Gene expression profiles and clinical features are collected from TCGA and GEO, and data analysis is performed in R4.2.0.

RESULTS

The ARGs-based no-supervised learning algorithm identifies three ARG subgroups, amongst which the prognosis is different. WCGNA and Artificial intelligence (AI) are applied to construct an NKE-related drug sensitivity stratification and prognosis identification model in digestive system cancer. Pathways association analysis screens out GLI2 is a key gene in regulating NKE by non-classic Hedgehog signaling (GLI2/TGF-β/IL6). In vitro experiments show that down-regulation of GLI2 enhances the CAPE-mediated cell toxicity and accompanies with down-regulation of PD-L1, tumor-derive IL6, and snial1 whereas the expression of cleaved caspas3, cleaved caspase4, cleaved PARP, and E-cadherin are up-regulated in colorectal cancer. Co-culture experiments show that GLI2- decreased colorectal tumor cells lead to down-regulation of TIM-3 and PD1 in NK cells, which are restored by TGF-bate active protein powder. Besides, the Elisa assay shows that GLI2-decreased colorectal tumor cells lead to up-regulation of IFN-gamma in NK cells.

Genetic diagnosis of congenital hypopituitarism in Turkish patients by a target gene panel: novel pathogenic variants in GHRHR, GLI2, LHX4 and POU1F1 genes

Objective

Congenital hypopituitarism (CH) is a rare disease characterized by one or more hormone deficiencies of the pituitary gland. To date, many genes have been associated with CH. In this study, we identified the allelic variant spectrum of 11 causative genes in Turkish patients with CH.

Materials and methods

This study included 47 patients [21 girls (44.6%) and 26 boys (55.4%)] from 45 families. To identify the genetic etiology, we screened 11 candidate genes associated with CH using next-generation sequencing. To confirm and detect the status of the specific familial variant in relatives, Sanger sequencing was also performed.

Results

We identified 12 possible pathogenic variants in GHRHR, GH1, GLI2, PROP-1, POU1F1, and LHX4 in 11 patients (23.4%), of which six were novel variants: two in GHRHR, two in POU1F1, one in GLI2, and one in LHX4. In all patients, these variants were most frequently found in GLI2, followed by PROP-1 and GHRHR.

Conclusion

Genetic causes were determined in only 23.4% of all patients with CH and 63% of molecularly diagnosed patients (7/11) from consanguineous families. Despite advances in genetics, we were unable to identify the genetic etiology of most patients with CH, suggesting the effect of unknown genes or environmental factors. More genetic studies are necessary to understand the etiology of CH.

Circular RNA circ-FIRRE interacts with HNRNPC to promote esophageal squamous cell carcinoma progression by stabilizing GLI2 mRNA

Increasing evidence has shown that circular RNAs (circRNAs) interact with RNA-binding proteins (RBPs) and promote cancer progression. However, the function and mechanism of the circRNA/RBP complex in esophageal squamous cell carcinoma (ESCC) are still largely unknown. Herein, we first characterized a novel oncogenic circRNA, circ-FIRRE, by RNA sequencing (Ribo-free) profiling of ESCC samples. Furthermore, we observed marked circ-FIRRE overexpression in ESCC patients with high TNM stage and poor overall survival. Mechanistic studies indicated that circ-FIRRE, as a platform, interacts with the heterogeneous nuclear ribonucleoprotein C (HNRNPC) protein to stabilize GLI2 mRNA by directly binding to its 3'-UTR in the cytoplasm, thereby resulting in elevated GLI2 protein expression and subsequent transcription of its target genes MYC, CCNE1, and CCNE2, ultimately contributing to ESCC progression. Moreover, HNRNPC overexpression in circ-FIRRE knockdown cells notably abolished circ-FIRRE knockdown-mediated Hedgehog pathway inhibition and ESCC progression impairment in vitro and in vivo. Clinical specimen results showed that circ-FIRRE and HNRNPC expression was positively correlated with GLI2 expression, which reveals the clear significance of the circ-FIRRE/HNRNPC-GLI2 axis in ESCC. In summary, our results indicate that circ-FIRRE could serve as a valuable biomarker and potential therapeutic target for ESCC and highlight a novel mechanism of the circ-FIRRE/HNRNPC complex in ESCC progression regulation.

Case report: A case of Culler-Jones syndrome caused by a novel mutation of GLI2 gene and literature review

Culler-Jones syndrome is a rare clinical phenomenon with diverse manifestations and is prone to misdiagnosis. We report one patient who presented with a 10-year history of anosmia and a 1-year history of epididymal pain. Kallmann syndrome was suspected initially. The results of his laboratory tests, imaging, and genetic testing, however, combined to provide a conclusive diagnosis of Culler-Jones syndrome. With the aid of high-throughput sequencing technology, the GLI2 gene c.527A>G (p.Tyr176Cys) heterozygous mutation in the child was identified. No published works have yet described this mutation site. We described Culler-Jones syndrome in a child at length. We recommend that Culler-Jones syndrome be taken into account when considering the spectrum of disorders associated with abnormal growth and development in children. Once diagnosed, individualized hormone replacement treatment is required for each patient.

Combinatorial Gli activity directs immune infiltration and tumor growth in pancreatic cancer

Proper Hedgehog (HH) signaling is essential for embryonic development, while aberrant HH signaling drives pediatric and adult cancers. HH signaling is frequently dysregulated in pancreatic cancer, yet its role remains controversial, with both tumor-promoting and tumor-restraining functions reported. Notably, the GLI family of HH transcription factors (GLI1, GLI2, GLI3), remain largely unexplored in pancreatic cancer. We therefore investigated the individual and combined contributions of GLI1-3 to pancreatic cancer progression. At pre-cancerous stages, fibroblast-specific Gli2/Gli3 deletion decreases immunosuppressive macrophage infiltration and promotes T cell infiltration. Strikingly, combined loss of Gli1/Gli2/Gli3 promotes macrophage infiltration, indicating that subtle changes in Gli expression differentially regulate immune infiltration. In invasive tumors, Gli2/Gli3 KO fibroblasts exclude immunosuppressive myeloid cells and suppress tumor growth by recruiting natural killer cells. Finally, we demonstrate that fibroblasts directly regulate macrophage and T cell migration through the expression of Gli-dependent cytokines. Thus, the coordinated activity of GLI1-3 directs the fibroinflammatory response throughout pancreatic cancer progression.

Truncating and zinc-finger variants in GLI2 are associated with hypopituitarism

Variants in transcription factor GLI2 have been associated with hypopituitarism and structural brain abnormalities, occasionally including holoprosencephaly (HPE). Substantial phenotypic variability and nonpenetrance have been described, posing difficulties in the counseling of affected families. We present three individuals with novel likely pathogenic GLI2 variants, two with truncating and one with a de novo missense variant p.(Ser548Leu), and review the literature for comprehensive phenotypic descriptions of individuals with confirmed pathogenic (a) intragenic GLI2 variants and (b) chromosome 2q14.2 deletions encompassing only GLI2. We show that most of the 31 missense variants previously reported as pathogenic are likely benign or, at most, low-risk variants. Four Zn-finger variants: p.(Arg479Gly), p.(Arg516Pro), p.(Gly518Lys), and p.(Tyr575His) were classified as likely pathogenic, and three other variants as possibly pathogenic: p.(Pro253Ser), p.(Ala593Val), and p.(Pro1243Leu). We analyze the phenotypic descriptions of 60 individuals with pathogenic GLI2 variants and evidence a morbidity spectrum that includes hypopituitarism (58%), HPE (6%) or other brain structure abnormalities (15%), orofacial clefting (17%) and dysmorphic facial features (35%). We establish that truncating and Zn-finger variants in GLI2 are associated with a high risk of hypopituitarism, and that a solitary median maxillary central incisor is part of the GLI2-related phenotypic variability. The most prevalent phenotypic feature is post-axial polydactyly (65%) which is also the mildest phenotypic expression of the condition, reported in many parents of individuals with systemic findings. Our approach clarifies clinical risks and the important messages to discuss in counseling for a pathogenic GLI2 variant.

Pharmacological Inhibition of Sonic Hedgehog Signaling Suppresses Tumor Development in a Murine Model of Intrahepatic Cholangiocarcinoma

Cholangiocarcinoma (CCC) is the second most primary liver cancer with an aggressive biological behavior, and its incidence increases steadily. An aberrant up-regulation of the sonic hedgehog signaling pathway has been reported in a variety of hepatic diseases including hepatic inflammation, fibrosis, as well as cancer. In this study, we determined the effect of a sonic hedgehog inhibitor, vismodegib, on the development of CCC. Through database analyses, we found sonic hedgehog signaling was up-regulated in human CCC, based on overexpression of its target genes, GLI1 and GLI2. Further, human CCC cells were highly sensitive to the treatment with vismodegib in vitro. Based on the data, we investigated the in vivo anti-cancer efficacy of vismodegib in CCC employing a murine model of CCC developed by hydrodynamic tail vein injection method. In the murine model, CCC induced by constitutively active forms of TAZ and PI3K exhibited up-regulated sonic hedgehog signaling. Treatment of vismodegib significantly suppressed tumor development in the murine CCC model, based on comparison of gross morphologies and liver weight/body weight. It is expected that pharmacological inhibition of sonic hedgehog signaling would be an effective molecular target therapy for CCC.

Postnatal deletion of Bmal1 in mice protects against obstructive renal fibrosis via suppressing Gli2 transcription

Circadian clock is involved in regulating most renal physiological functions, including water and electrolyte balance and blood pressure homeostasis, however, the role of circadian clock in renal pathophysiology remains largely unknown. Here we aimed to investigate the role of Bmal1, a core clock component, in the development of renal fibrosis, the hallmark of pathological features in many renal diseases. The inducible Bmal1 knockout mice (iKO) whose gene deletion occurred in adulthood were used in the study. Analysis of the urinary water, sodium and potassium excretion showed that the iKO mice exhibit abolished diurnal variations. In the model of renal fibrosis induced by unilateral ureteral obstruction, the iKO mice displayed significantly decreased tubulointerstitial fibrosis reflected by attenuated collagen deposition and mitigated expression of fibrotic markers α-SMA and fibronectin. The hedgehog pathway transcriptional effectors Gli1 and Gli2, which have been reported to be involved in the pathogenesis of renal fibrosis, were significantly decreased in the iKO mice. Mechanistically, ChIP assay and luciferase reporter assay revealed that BMAL1 bound to the promoter of and activate the transcription of Gli2, but not Gli1, suggesting that the involvement of Bmal1 in renal fibrosis was possibly mediated via Gli2-dependent mechanisms. Furthermore, treatment with TGF-β increased Bmal1 in cultured murine proximal tubular cells. Knockdown of Bmal1 abolished, while overexpression of Bmal1 increased, Gli2 and the expression of fibrosis-related genes. Collectively, these results revealed a prominent role of the core clock gene Bmal1 in tubulointerstitial fibrosis. Moreover, we identified Gli2 as a novel target of Bmal1, which may mediate the adverse effect of Bmal1 in obstructive nephropathy.

Xpo7 negatively regulates Hedgehog signaling by exporting Gli2 from the nucleus

Dynamic bidirectional transport between the nucleus and the cytoplasm is critical for the regulation of many transcription factors, whose levels inside the nucleus must be tightly controlled. Efficient shuttling across the nuclear membrane is especially crucial with regard to the Hedgehog (Hh) pathway, where the transcriptional signal depends on the fine balance between the amounts of Gli protein activator and repressor forms in the nucleus. The nuclear export machinery prevents the unchecked nuclear accumulation of Gli proteins, but the mechanistic insight into this process is limited. We show that the atypical exportin Xpo7 functions as a major nuclear export receptor that actively excludes Gli2 from the nucleus and controls the outcome of Hh signaling. We show that Xpo7 interacts with several domains of Gli2 and that this interaction is modulated by SuFu, a key negative regulator of Hh signaling. Our data pave the way for a more complete understanding of the nuclear shuttling of Gli proteins and the regulation of their transcriptional activity.

MicroRNA-155 is upregulated in the placentas of patients with preeclampsia and affects trophoblast apoptosis by targeting SHH/GLi1/BCL2

The pathogenesis of preeclampsia (PE) is complicated and multiple risk factors have been associated with its occurrence. Still, the underlying molecular mechanisms involved in PE remain elusive. Aberrant apoptosis and insufficient invasion of trophoblasts have been observed and are considered vital pathological features in PE. Herein, we found that miR-155 can specifically degrade the mRNA of the Hedgehog ligand sonic hedgehog (SHH), using dual luciferase reporter assays. Quantitative real-time PCR found that administering miR-155 mimics or inhibitors could significantly decrease or increase the expression of SHH in the trophoblasts, respectively. The transcription levels of miR-155 in the placenta were higher in patients with PE compared to the levels in healthy pregnant women, as shown by quantitative real-time PCR. Serum levels of miR-155 could predict the diagnosis of PE by receiver operating characteristic curve analysis and diagnosis evaluation tests. A significant increase in apoptosis was observed after administering miR-155 in HTR8/SVneo cells cultured ex vivo, accompanied by reduced proliferation. Mechanistically, transcriptional activity and expression of GLi1 were also inhibited under treatment of miR-155, and could be recovered after supplying additional recombinant human SHH to primary trophoblasts from patients, as determined by luciferase activity assays and western blotting. We further found that inhibiting miR-155 increased the production of SHH and improved the phenotype in primary trophoblasts from patients with PE. Our data show that miR-155 regulates apoptosis of trophoblasts in PE, which has potential value for predicting PE risk and might be deemed as a therapeutic target for treating PE.

Positive feedback of SuFu negating protein 1 on Hedgehog signaling promotes colorectal tumor growth

Hedgehog (Hh) signaling plays a critical role in embryogenesis and tissue homeostasis, and its deregulation has been associated with tumor growth. The tumor suppressor SuFu inhibits Hh signaling by preventing the nuclear translocation of Gli and suppressing cell proliferation. Regulation of SuFu activity and stability is key to controlling Hh signaling. Here, we unveil SuFu Negating Protein 1 (SNEP1) as a novel Hh target, that enhances the ubiquitination and proteasomal degradation of SuFu and thus promotes Hh signaling. We further show that the E3 ubiquitin ligase LNX1 plays a critical role in the SNEP1-mediated degradation of SuFu. Accordingly, SNEP1 promotes colorectal cancer (CRC) cell proliferation and tumor growth. High levels of SNEP1 are detected in CRC tissues and are well correlated with poor prognosis in CRC patients. Moreover, SNEP1 overexpression reduces sensitivity to anti-Hh inhibitor in CRC cells. Altogether, our findings demonstrate that SNEP1 acts as a novel feedback regulator of Hh signaling by destabilizing SuFu and promoting tumor growth and anti-Hh resistance.

HOTAIR and androgen receptor synergistically increase GLI2 transcription to promote tumor angiogenesis and cancer stemness in renal cell carcinoma

Tumor angiogenesis is a major characteristic of renal cell carcinoma (RCC). Herein, we report a novel mechanism of how lncRNA and androgen receptor (AR) drive the Hedgehog pathway to promote tumor angiogenesis in RCC. We found that the high expression of lncRNA HOTAIR in RCC is associated with poor prognosis. Moreover, HOTAIR and AR form a feedback loop to promote the expression of each other. Interestingly, we also found that in RCC, HOTAIR is associated with the Hedgehog pathway, especially GLI2, via bioinformatics analysis. Furthermore, HOTAIR promotes GLI2 expression in the presence of AR. Mechanistically, HOTAIR interacts with AR and they cooperatively bind to GLI2 promoter and increase its transcription activity. We further confirmed how HOTAIR-AR axis regulates GLI2 expression by analyzing its function in RCC cells and found that HOTAIR and AR synergistically enhanced the expression of GLI2 downstream genes, such as VEGFA, PDGFA, and cancer stem cell transcription factors, and promoted tumor angiogenesis and cancer stemness in RCC cells both in vitro and in tumor xenografts. Overall, these findings suggest that HOTAIR and GLI2 could be novel therapeutic targets against RCC.

Natural small molecule triptonide inhibits lethal acute myeloid leukemia with FLT3-ITD mutation by targeting Hedgehog/FLT3 signaling

Acute myeloid leukemia harboring internal tandem duplication of FMS-like tyrosine kinase 3 (FLT3-ITD AML) is a subset of highly aggressive malignancies with poor clinical outcome. Despite some advances in the development of FLT3 tyrosine kinase inhibitors (FLT3 inhibitors), most of FLT3-ITD AML patients suffer from lethal disease relapse, suggesting the requirement of novel targets and agents. Here we describe a natural small molecule, triptonide that can efficiently inhibit FLT3-ITD-driven AML in vitro and in vivo. Mechanistically, triptonide targeted Hedgehog/FLT3 signaling by inhibiting its critical effectors, which are GLI2, c-Myc and FLT3 and induced apoptosis of FLT3-ITD-driven leukemia cells. In addition, we also observed that triptonide activated tumor suppressor p53. In vivo, triptonide treatment markedly suppressed lethal FLT3-ITD-driven AML with good tolerance and prolonged survival time in orthotopic mouse model. Our studies identify Hedgehog/FLT3 axis as a novel target for treating FLT3-ITD-driven leukemia and demonstrate that triptonide is an active lead compound that can kill FLT3-ITD-driven leukemia cells.

Long non-coding RNA HOTAIR induces GLI2 expression through Notch signalling in systemic sclerosis dermal fibroblasts

OBJECTIVES

Systemic sclerosis (SSc) is characterised by tissue fibrosis of the major organs of the body including the skin, lungs and heart. We have previously reported that the lncRNA HOTAIR plays a central role in the activation of SSc myofibroblasts, the key cellular elements of fibrosis. HOTAIR induces fibroblast activation through H3K27me3-mediated activation of the Notch signalling pathway. Here we aimed to identify the signalling events downstream of Notch that drive SSc myofibroblast activation.

METHODS

Patient fibroblasts were obtained from full-thickness forearm skin biopsies of 3 adult patients with SSc of recent onset. The lncRNA HOTAIR was expressed in healthy dermal fibroblasts by lentiviral transduction. Hedgehog signalling pathway was inhibited with GANT61 and GLI2 siRNA. Gamma secretase inhibitors RO4929097 and DAPT were used to block Notch signalling. GSK126 was used to inhibit Enhancer of Zeste 2 (EZH2).

RESULTS

Overexpression of HOTAIR in dermal fibroblasts induced the expression of the Hedgehog pathway transcription factor GLI2. This is mediated by activation of Notch signalling following epigenetic downregulation of miRNA-34a expression. Inhibition of H3K27 methylation and Notch signalling reduced expression of GLI2 in HOTAIR-expressing fibroblasts as well as in SSc dermal fibroblasts. Importantly, the inhibition of GLI2 function using GANT61 or siRNA mitigates the pro-fibrotic phenotype induced by HOTAIR.

CONCLUSIONS

Our data indicates that GLI2 expression is stably upregulated in SSc myofibroblasts through HOTAIR and that GLI2 mediates the expression of pro-fibrotic markers downstream of Notch.

Optic vesicle morphogenesis requires primary cilia

Arl13b is a gene known to regulate ciliogenesis. Functional alterations in this gene's activity have been associated with Joubert syndrome. We found that in Arl13 null mouse embryos the orientation of the optic cup is inverted, such that the lens is abnormally surrounded by an inverted optic cup whose retina pigmented epithelium is oddly facing the surface ectoderm. Loss of Arl13b leads to the disruption of optic vesicle's patterning and expansion of ventral fates. We show that this phenotype is consequence of miss-regulation of Sonic hedgehog (Shh) signaling and demonstrate that the Arl13b-/- eye phenotype can be rescued by deletion of Gli2, a downstream effector of the Shh pathway. This work identified an unexpected role of primary cilia during the morphogenetic movements required for the formation of the eye.

Hedgehog Signal Inhibitor GANT61 Inhibits the Malignant Behavior of Undifferentiated Hepatocellular Carcinoma Cells by Targeting Non-Canonical GLI Signaling

The Hedgehog (HH)–GLI pathway plays an important role in cell dedifferentiation and is therefore pivotally involved in the malignant transformation of cancer cells. GANT61, a selective inhibitor of GLI1 and GLI2, was reported as a promising treatment for cancer in various tissues; however, the biological impact of GANT61 in hepatocellular carcinoma (HCC), especially in undifferentiated HCC cells, remains unclear. In this study, we investigated the antitumor effect of GANT61 using two undifferentiated hepatoma cell lines: HLE and HLF. Quantitative PCR and RT-PCR analyses revealed that these cells express GLI transcripts, showing mesenchymal phenotypes characterized by the loss of epithelial and hepatic markers and specific expression of epithelial–mesenchymal transition (EMT)-related genes. GANT61 significantly reduced the proliferation and cell viability after drug treatment using 5-FU and Mitomycin C. We showed that GLI transcript levels were down-regulated by the MEK inhibitor U0126 and the Raf inhibitor sorafenib, suggesting that non-canonical signaling including the Ras–Raf–MEK–ERK pathway is involved. Sphere formation and migration were significantly decreased by GANT61 treatment, and it is suggested that the underlying molecular mechanisms are the down-regulation of stemness-related genes (Oct4, Bmi1, CD44, and ALDH) and the EMT-related gene Snail1. The data presented here showed that direct inhibition of GLI might be beneficial for the treatment of dedifferentiated HCC.

Unique near-complete deletion of GLI2 in a patient with combined pituitary hormone deficiency and post-axial polydactyly

INTRODUCTION

Combined pituitary hormone deficiency (CPHD) can cause a broad spectrum of health problems, ranging from short stature only, to convulsions or even death. In the majority of patients, the cause is unknown.

METHODS

The idex case had unexplained CPHD, pituitary anomalies on MRI and polydactyly. In the patients and her unaffected parents, we performed SNP array analysis and Whole Exome Sequencing, after candidate gene analysis turned out negative.

RESULTS

We found a unique de novo heterozygous 229.9 kb deletion in the index case on chr. 2q14.2. This deletion covered 12 out of the 13 coding exons of the GLI2 gene, a transcription factor involved in midline formation and previously associated with CPHD. As reported GLI2 deletions and mutations show a large phenotypic variability, we performed a genotype-phenotype analysis. This revealed that GLI2 missense mutations usually present with a 'ppp-only' phenotype (pituitary anomalies ± postaxial polydactyly without brain phenotype), whereas the 'ppp-plus' phenotype (with major brain malformations and/or intellectual disabilities) is more frequent in patients with larger deletions, and those with frameshift mutations/point mutations or splice variants resulting in a stop codon (p < .001).

CONCLUSION

The present case shows that a deletion of the GLI2 gene only (not affecting any of the adjacent genes) causes pituitary anomalies without brain phenotype. This suggests that brain phenotype only occurs when additional genes adjacent to GLI2 are deleted, or when mutations result in truncated GLI2 mRNA/protein. However, due to the lack of functional data for many GLI2 mutations and based on the available information regarding variable penetrance, phenotype-genotype correlations need to be made with caution.

Saikosaponin B2 attenuates kidney fibrosis via inhibiting the Hedgehog Pathway

BACKGROUND

Renal interstitial fibrosis is a common pathway through which chronic kidney disease progresses to end-stage renal disease. There are currently no effective drugs available to treat kidney fibrosis, so traditional medicine is likely to be a candidate. The therapeutic potential of saikosaponin B2 (SSB2), a biologically active ingredient of Radix Bupleuri, on renal fibrosis has not been reported.

METHODS

A unilateral ureteral obstruction (UUO) model was conducted to induce renal interstitial fibrosis in mice. SSB2's effect was valuated by histological staining and exploring the changes in expression of relative proteins and mRNAs. A conditional medium containing sonic hedgehog variant protein stimulating normal rat kidney interstitial fibroblast cells (NRK-49F) was used in an in vitro model to determine the possible mechanism. The molecular target of SSB2 was verified using several mutation plasmids.

RESULTS

SSB2 administration reduced kidney injury and alleviated interstitial fibrosis by decreasing excessive accumulation of extracellular matrix components in UUO mice. It could also reduce the expression of α-SMA, fibronectin and Gli1, a crucial molecule of the hedgehog (Hh) signaling pathway both in vivo and in vitro. In NIH-3T3 cells simulated by conditional medium containing sonic hedgehog variant protein, SSB2 showed the ability to decrease the expression of Gli1 and Ptch1 mRNA. Using a dual-luciferase reporter assay, SSB2 suppressed the Gli-luciferase reporter activity in NIH-3T3 cells, and the IC₅₀ was 0.49 μM, but had no effect on the TNF-α/NF-κB and Wnt/β-catenin signaling pathways, indicating the inhibition selectivity on the Hh signaling pathway. Furthermore, SSB2 failed to inhibit the Hh pathway activity evoked by ectopic expression of Gli2ΔN and Smo D473H, suggesting that SSB2 might potentially act on smoothened receptors.

CONCLUSION

SSB2 could attenuate renal fibrosis and decrease fibroblast activation by inhibiting the Hh signaling pathway.

USP8 mutations in corticotroph adenomas determine a distinct gene expression profile irrespective of functional tumour status

OBJECTIVE

Pituitary corticotroph adenomas commonly cause Cushing's disease (CD) but part of these tumours are hormonally inactive (silent corticotroph adenomas, SCA). USP8 mutations are well-known driver mutations in corticotrophinomas. Differences in transcriptomic profiles between functioning and silent tumours or tumours with different USP8 status have not been investigated.

DESIGN AND METHODS

Forty-eight patients (28 CD, 20 SCA) were screened for USP8 mutations with Sanger sequencing. Twenty-four patients were included in transcriptomic profiling with Ampliseq Transcriptome Human Gene Expression Core Panel. The entire patients group was included in qRT-PCR analysis of selected genes expression. Immunohistochemistry was used for visualization of selected protein.

RESULTS

We found USP8 mutation in 15 patients with CD and 4 SCAs. USP8 mutations determine molecular profile of the tumours as showed by hierarchical clustering and identification of 1648 genes differentially expressed in USP8-mutated and USP8-wild-type tumours. Mutations affect many molecular pathways as observed in Gene Set Enrichment analysis. USP8-mutated adenomas showed higher level of POMC, CDC25A, MAPK4 but lower level of CCND2, CDK6, CDKN1B than USP8-wt tumours. Eighty-seven genes differentially expressed between CD-related adenomas and SCAs were found, including those involved in cell signalling (GLI2, DLC1, TBX2, RASSF6), cell adhesion (GJA1, CDH6), ion transport (KCNN4, KCNJ5) and GABA signalling (GABBR2, GABRD).

CONCLUSION

USP8 mutations occur in functioning and silent corticotrophinomas. They have pleiotropic effect, not limited to EGFR signalling, and affect expression levels of many genes involved in different pathways. Expression of GABA-related genes GABBR2, GNAL, GABARD and KCNJ5 correspond to functional status of the tumours.

Elucidation of mechanism for host response to VHSV infection at varying temperatures in vitro and in vivo through proteomic analysis

Seasonal temperature has a major influence on the infectivity of pathogens and the host immune system. Viral hemorrhagic septicemia virus (VHSV) is one such pathogen that only causes the mortality of fish at low temperatures. This study aims to discover the host defense mechanism and pathway for resistance to VHSV at higher temperatures. We first observed the VHSV infection patterns at low and higher temperatures in fathead minnow (FHM) cells (20 °C and 28 °C) and zebrafish (15 °C and 25 °C). In comparison to the 20 °C infection, FHM cells infected at 28 °C showed decreased apoptosis, increased cell viability, and reduced VHSV N gene expression. In zebrafish, infection at 25 °C caused no mortality and significantly reduced the N gene copy number in comparison to infection at 15 °C. To explore the antiviral infection mechanisms induced by high temperature in vitro and in vivo, the changes in the proteomic profile were measured through UPLC-MS^E analysis. ACADL, PTPN6, TLR1, F7, A2M, and GLI2 were selected as high temperature-specific biomarkers in the FHM cell proteome; and MYH9, HPX, ANTXR1, APOA1, HBZ, and MYH7 were selected in zebrafish. Increased immune response, anticoagulation effects, and the formation of lymphocytes from hematopoietic stem cells were analyzed as functions that were commonly induced by high temperature in vitro and in vivo. Among these biomarkers, GLI2 was predicted as an upstream regulator. When treated with GANT58, a GLI-specific inhibitor, cell viability was further reduced due to GLI2 inhibition during VHSV infection at varying temperatures in FHM cells, and the mortality in zebrafish was induced earlier at the low temperature. Overall, this study discovered a new mechanism for VHSV infection in vitro and in vivo that is regulated by GLI2 protein.

Mutation in NADPH oxidase 3 (NOX3) impairs SHH signaling and increases cerebellar neural stem/progenitor cell proliferation

Abnormalities in cerebellar structure and function may cause ataxia, a neurological dysfunction of motor coordination. In the course of the present study, we characterized a mutant mouse lineage with an ataxia-like phenotype. We localized the mutation on chromosome 17 and mapped it to position 1534 of the Nox3 gene, resulting in p.Asn64Tyr change. The primary defect observed in Nox3^eqlb mice was increased proliferation of cerebellar granule cell precursors (GCPs). cDNA microarray comparing Nox3^eqlb and BALB/c neonatal cerebellum revealed changes in the expression of genes involved in the control of cell proliferation. Nox3^eqlb GCPs and NSC produce higher amounts of reactive oxygen species (ROS) and upregulate the expression of SHH target genes, such as Gli1-3 and Ccnd1 (CyclinD1). We hypothesize that this new mutation is responsible for an increase in proliferation via stimulation of the SHH pathway. We suggest this mutant mouse lineage as a new model to investigate the role of ROS in neuronal precursor cell proliferation.

The sonic hedgehog signaling pathway is suppressed following PCB1254 exposure during retinal development

Polychlorinated biphenyl (PCB) has been reported to have detrimental effects on retinal development. In order to explore the role of Shh signaling in retinal development after PCB₁₂₅₄ exposure in vivo and in vitro, zebrafish and RGC-5 retinal cell line were used. Compared with the controls, PCB exposure inhibited proliferation and increased the apoptosis levels. The expression of Shh mRNA decreased in the PCB₁₂₅₄ -treated groups both in vivo and in vitro compared with that of the controls. The ptch2 mRNA expression increased in the experimental groups. The expression of gli2 mRNA decreased in the PCB₁₂₅₄ -treated groups. Immunofluorescence and western blotting assays confirmed that the expression of Shh proteins decreased in PCB₁₂₅₄ -treated groups compared with control groups. Moreover, ptch2 protein levels increased in the PCB₁₂₅₄ -treated groups as well as the decreased protein expressions of gli1 and gli2. These results demonstrated that Shh signaling pathway may participate in the damage of retinal development caused by PCB₁₂₅₄ exposure, providing evidence that eye diseases could be caused by environmental pollutants.

Novel GLI2 mutations identified in patients with Combined Pituitary Hormone Deficiency (CPHD): Evidence for a pathogenic effect by functional characterization

CONTEXT

The Gli-family of zinc-finger transcription factors regulates the Sonic Hedgehog (Shh) signalling pathway that plays a key role in early pituitary and ventral forebrain development. Heterozygous GLI2 loss of function mutations in humans have been reported in holoprosencephaly (HPE), HPE-like phenotypes associated with pituitary anomalies and combined pituitary hormone deficiency with or without other extra-pituitary findings.

OBJECTIVE

The aim of this study was the search for GLI2 mutations in a cohort of Italian CPHD patients and the assessment of a pathogenic role for the identified variants through in vitro studies.

PATIENTS

One hundred forty-five unrelated CPHD patients diagnosed with or without extra-pituitary manifestations were recruited from different Italian centres.

METHODS

The GLI2 mutation screening was carried out through direct sequencing of all the 13 exons and intron-exon boundaries. Luciferase reporter assays were performed to evaluate the role of the detected missense variants.

RESULTS

Five different novel heterozygous non-synonymous GLI2 variants were identified in five patients. The mutations were three missense (p.Pro386Leu, p.Tyr575His, p.Ala593Val), one frameshift (p.Val1111Glyfs*19) and one nonsense (p.Arg1226X). The latter two mutants are likely pathogenic since they lead to a truncated protein. The in vitro functional study of the plasmids bearing two of the three missense variants (namely p.Tyr575His and p.Ala593Val) revealed a significant reduction in transcriptional activity.

CONCLUSION

In conclusion, the analysis of GLI2 in individuals with CPHD led to the identification of five variations with a likely negative impact on the GLI2 protein, confirming that GLI2 is an important causative gene in CPHD. The functional in vitro study analysis performed on the missense variations were useful to strengthen the hypothesis of pathogenicity.

Genetic deletion of genes in the cerebellar rhombic lip lineage can stimulate compensation through adaptive reprogramming of ventricular zone-derived progenitors

BACKGROUND

The cerebellum is a foliated posterior brain structure involved in coordination of motor movements and cognition. The cerebellum undergoes rapid growth postnataly due to Sonic Hedgehog (SHH) signaling-dependent proliferation of ATOH1+ granule cell precursors (GCPs) in the external granule cell layer (EGL), a key step for generating cerebellar foliation and the correct number of granule cells. Due to its late development, the cerebellum is particularly vulnerable to injury from preterm birth and stress around birth. We recently uncovered an intrinsic capacity of the developing cerebellum to replenish ablated GCPs via adaptive reprogramming of Nestin-expressing progenitors (NEPs). However, whether this compensation mechanism occurs in mouse mutants affecting the developing cerebellum and could lead to mis-interpretation of phenotypes was not known.

METHODS

We used two different approaches to remove the main SHH signaling activator GLI2 in GCPs: 1) Our mosaic mutant analysis with spatial and temporal control of recombination (MASTR) technique to delete Gli2 in a small subset of GCPs; 2) An Atoh1-Cre transgene to delete Gli2 in most of the EGL. Genetic Inducible Fate Mapping (GIFM) and live imaging were used to analyze the behavior of NEPs after Gli2 deletion.

RESULTS

Mosaic analysis demonstrated that SHH-GLI2 signaling is critical for generating the correct pool of granule cells by maintaining GCPs in an undifferentiated proliferative state and promoting their survival. Despite this, inactivation of GLI2 in a large proportion of GCPs in the embryo did not lead to the expected dramatic reduction in the size of the adult cerebellum. GIFM uncovered that NEPs do indeed replenish GCPs in Gli2 conditional mutants, and then expand and partially restore the production of granule cells. Furthermore, the SHH signaling-dependent NEP compensation requires Gli2, demonstrating that the activator side of the pathway is involved.

CONCLUSION

We demonstrate that a mouse conditional mutation that results in loss of SHH signaling in GCPs is not sufficient to induce long term severe cerebellum hypoplasia. The ability of the neonatal cerebellum to regenerate after loss of cells via a response by NEPs must therefore be considered when interpreting the phenotypes of Atoh1-Cre conditional mutants affecting GCPs.

Abnormal activity of transcription factors gli in high-grade gliomas

Malignant transformation is associated with loss of cell differentiation, anaplasia. Transcription factors gli, required for embryonic development, may be involved in this process. We studied the activity of transcription factors gli in high-grade gliomas and their role in maintenance of stem cell state and glioma cell survival. 20 glioma cell lines and a sample of a normal adult brain tissue were used in the present study. We found the expression of gli target genes, including GLI1 and FOXM1, in all tested glioma cell lines, but not in the normal tissue. Interestingly, the expression of gli target genes in some glioma cell lines was observed together with a high level of their transcriptional repressor, Gli3R. Knockdown of GLI3 in one of these lines resulted in decrease of gli target gene expression. These data suggest that Gli3R does not prevent the gli target genes transcription, and gli3 acts in glioma cells more as an activator, than a repressor of transcription. We observed that gli regulated the expression of such genes, as SOX2 or OCT4 that maintain stem cell state, and TET1, involving in DNA demethylation. Treatment with GANT61 or siRNA against GLI1, GLI2, or GLI3 could result in complete glioma cell death, while cyclopamine had a weaker and line-specific effect on glioma cell survival. Thus, the gli transcription factors are abnormally active in high-grade gliomas, regulate expression of genes, maintaining the stem cell state, and contribute to glioma cell survival.

A novel GLI2 mutation responsible for congenital hypopituitarism and polymalformation syndrome

OBJECTIVE

We report a novel GLI2 frameshift mutation and describe the phenotypic spectrum of mutations within this gene.

PATIENTS AND METHODS

A male with congenital hypopituitarism and polymalformation syndrome was clinically, biochemically and neuroradiologically characterized. Genetic analysis for congenital hypopituitarism was performed using a targeted NGS custom gene panel.

RESULTS

A heterozygous frameshift mutation, NM_005270.4:c.2125del, p.(Leu709Trpfs*15), was identified in GLI2 exon 12. This mutation has not been previously reported and confirms the diagnosis of Culler-Jones syndrome (MIM #615849).

CONCLUSION

GLI2 mutations should be suspected in the presence of congenital hypopitutarism, characteristic facial abnormalities and polydactyly.

A novel truncating variant of GLI2 associated with Culler-Jones syndrome impairs Hedgehog signalling

Background

GLI2 encodes for a transcription factor that controls the expression of several genes in the Hedgehog pathway. Mutations in GLI2 have been described as causative of a spectrum of clinical phenotypes, notably holoprosencephaly, hypopituitarism and postaxial polydactyl.

Methods

In order to identify causative genetic variant, we performed exome sequencing of a trio from an Italian family with multiple affected individuals presenting clinical phenotypes in the Culler-Jones syndrome spectrum. We performed a series of cell-based assays to test the functional properties of mutant GLI2.

Results

Here we report a novel deletion c.3493delC (p.P1167LfsX52) in the C-terminal activation domain of GLI2. Functional assays confirmed the pathogenicity of the identified variant and revealed a dominant-negative effect of mutant GLI2 on Hedgehog signalling.

Conclusions

Our results highlight the variable clinical manifestation of GLI2 mutations and emphasize the value of functional characterisation of novel gene variants to assist genetic counselling and diagnosis.

Sonic Hedgehog Signalling Activation Contributes to ALCAM Over-Expression and Poor Clinical Outcome in Patients with Oral Squamous Cell Carcinoma

OBJECTIVE

To investigate the Sonic Hedgehog (SHH) signalling molecules and activated leukocyte cell adhesion molecule (ALCAM) expression in the mechanisms regulating invasion and metastasis in oral squamous cell carcinoma (OSCC).

METHODS

The expressions of SHH signalling molecules Gli family zinc finger 1/2 (Gli1/Gli2), as well as ALCAM expression, was analysed in 101 OSCC patients by immunohistochemistry. The potential relationship between Gli1/Gli2 and ALCAM in regard to invasion and metastasis were studied by western blot, invasion and wound-healing assays.

RESULTS

Gli1, Gli2 and ALCAM were expressed in 54.5%, 49.5% and 47.5% of the 101 OSCC specimens, respectively. High expression of ALCAM was associated with shorter survival in the patient population (P = 0.018), which was independent of other clinical parameters. Notably, when both ALCAM expression and positive nodal status were considered, an enhanced prediction of clinical outcomes was achieved (P = 0.001). In OSCC cell lines, down-regulation of ALCAM resulted in reduced cell invasion and metastasis. Importantly, SHH activation increased the half-life of ALCAM leading to ALCAM accumulation and increased cell invasion and migration.

CONCLUSION

ALCAM over-expression in OSCC is an independent prognostic factor for OSCC patients. Its over-expression may be the result of the activation of the SHH signalling pathway and contributes to OSCC progression.

mTORC1-Mediated Inhibition of 4EBP1 Is Essential for Hedgehog Signaling-Driven Translation and Medulloblastoma

Mechanistic target of rapamycin (MTOR) cooperates with Hedgehog (HH) signaling, but the underlying mechanisms are incompletely understood. Here we provide genetic, biochemical, and pharmacologic evidence that MTOR complex 1 (mTORC1)-dependent translation is a prerequisite for HH signaling. The genetic loss of mTORC1 function inhibited HH signaling-driven growth of the cerebellum and medulloblastoma. Inhibiting translation or mTORC1 blocked HH signaling. Depleting 4EBP1, an mTORC1 target that inhibits translation, alleviated the dependence of HH signaling on mTORC1. Consistent with this, phosphorylated 4EBP1 levels were elevated in HH signaling-driven medulloblastomas in mice and humans. In mice, an mTORC1 inhibitor suppressed medulloblastoma driven by a mutant SMO that is inherently resistant to existing SMO inhibitors, prolonging the survival of the mice. Our study reveals that mTORC1-mediated translation is a key component of HH signaling and an important target for treating medulloblastoma and other cancers driven by HH signaling.