Positive regulation of Hedgehog signaling via phosphorylation of GLI2/GLI3 by DYRK2 kinase.

Hedgehog (Hh) signaling, an evolutionarily conserved pathway, plays an essential role in development and tumorigenesis, making it a promising drug target. Multiple negative regulators are known to govern Hh signaling; however, how activated Smoothened (SMO) participates in the activation of downstream GLI2 and GLI3 remains unclear. Herein, we identified the ciliary kinase DYRK2 as a positive regulator of the GLI2 and GLI3 transcription factors for Hh signaling. Transcriptome and interactome analyses demonstrated that DYRK2 phosphorylates GLI2 and GLI3 on evolutionarily conserved serine residues at the ciliary base, in response to activation of the Hh pathway. This phosphorylation induces the dissociation of GLI2/GLI3 from suppressor, SUFU, and their translocation into the nucleus. Loss of Dyrk2 in mice causes skeletal malformation, but neural tube development remains normal. Notably, DYRK2-mediated phosphorylation orchestrates limb development by controlling cell proliferation. Taken together, the ciliary kinase DYRK2 governs the activation of Hh signaling through the regulation of two processes: phosphorylation of GLI2 and GLI3 downstream of SMO and cilia formation. Thus, our findings of a unique regulatory mechanism of Hh signaling expand understanding of the control of Hh-associated diseases.

Hedgehog signaling pathway regulates Th17 cell differentiation in asthma via IL-6/STAT3 signaling.

Asthma is the most prevalent chronic inflammatory disease of the airways in children. The most prevalent phenotype of asthma is eosinophilic asthma, which is driven by a Th2 immune response and can be effectively managed by inhaled corticosteroid therapy. However, there are phenotypes of asthma with Th17 immune response that are insensitive to corticosteroid therapy and manifest a more severe phenotype. The treatment of this corticosteroid-insensitive asthma is currently immature and requires further attention. The objective of this study is to elucidate the regulation of the Hedgehog signaling pathway in Th17 cell differentiation in asthma. The study demonstrated that both Smo and Gli3, key components of the Hedgehog signaling pathway, were upregulated in Th17 polarization in vitro and in a Th17-dominant asthma model in vivo. Inhibiting Smo with a small molecule inhibitor or genetically knocking down Gli3 was found to suppress Th17 polarization. Smo was found to increase in Th1, Th2, Th17 and Treg polarization, while Gli3 specifically increased in Th17 polarization. ChIP-qPCR analyses indicated that Gli3 can directly interact with IL-6 in T cells, inducing STAT3 phosphorylation and promoting Th17 cell differentiation. Furthermore, the study demonstrated a correlation between elevated Gli3 expression and IL-17A and IL-6 expression in children with asthma. In conclusion, the study demonstrated that the Hedgehog signaling pathway plays an important role in the pathogenesis of asthma, as it regulates the differentiation of Th17 cells through the IL-6/STAT3 signaling. This may provide a potential therapeutic target for corticosteroid-insensitive asthma driven by Th17 cells.

Identification of truncated variants in GLI family zinc finger 3 (GLI3) associated with polydactyly.

BACKGROUND: Polydactyly is a prevalent congenital anomaly with an incidence of 2.14 per 1000 live births in China. GLI family zinc finger 3 (GLI3) is a classical causative gene of polydactyly, and serves as a pivotal transcription factor in the hedgehog signaling pathway, regulating the development of the anterior-posterior axis in limbs. METHODS: Three pedigrees of polydactyly patients were enrolled from Hunan Province, China. Pathogenic variants were identified by whole-exome sequencing (WES) and Sanger sequencing. RESULTS: Three variants in GLI3 were identified in three unrelated families, including a novel deletion variant (c.1372del, p.Thr458GlnfsTer44), a novel insertion-deletion (indel) variant (c.1967_1968delinsAA, p.Ser656Ter), and a nonsense variant (c.2374 C > T, p.Arg792Ter). These variants were present exclusively in patients but not in healthy individuals. CONCLUSIONS: We identified three pathogenic GLI3 variants in polydactyly patients, broadening the genetic spectrum of GLI3 and contributing significantly to genetic counseling and diagnosis for polydactyly.

Construction and Identification of a Novel Mice Model of Microphthalmia.

Purpose: Microphthalmia is a rare developmental eye disease that affects 1 in 7000 births. Currently, there is no cure for this condition. This study aimed to construct a stable mouse model of microphthalmia, thus providing a new tool for the study of the etiology of microphthalmia. Methods: The Hedgehog signaling pathway plays a crucial role in eye development. One of the key mechanisms of the Sonic Hedgehog signaling is the strong transcriptional activation ability of GLI3, a major mediator of this pathway. This study used CRISPR/Cas9 system to construct a novel TgGli3Ki/Ki lens-specific over-expression mouse line. To identify the ocular characteristics of this line, quantitative PCR, Western blot, hematoxylin and eosin staining, immunofluorescent staining, and RNA-seq were performed on the ocular tissues of this line and normal mice. Results: The TgGli3Ki/Ki lens-specific over-expression mouse model exhibits the ocular phenotype of microphthalmia. In the TgGli3Ki/Ki mouse, Gli3 is over-expressed in the lens, and the size of the eyeball and lens is significantly smaller than the normal one. RNA-seq analysis using the lens and the retina samples from TgGli3Ki/Ki and normal mice indicates that the phototransduction pathway is ectopically activated in the lens. Immunofluorescent staining of the lens samples confirmed this activation. Conclusions: The TgGli3Ki/Ki mouse model consistently manifests the stereotypical microphthalmia phenotype across generations, making it an excellent tool for studying this severe eye disease. Translational Relevance: This study developed a novel animal model to facilitate clinical research on microphthalmia.

A novel missense variant located within the zinc finger domain of the GLI3 gene was identified in a Vietnamese pedigree with index finger polydactyly.

BACKGROUND: Polydactyly, particularly of the index finger, remains an intriguing anomaly for which no specific gene or locus has been definitively linked to this phenotype. In this study, we conducted an investigation of a three-generation family displaying index finger polydactyly. METHODS: Exome sequencing was conducted on the patient, with a filtration to identify potential causal variation. Validation of the obtained variant was conducted by Sanger sequencing, encompassing all family members. RESULTS: Exome analysis uncovered a novel heterozygous missense variant (c.1482A>T; p.Gln494His) at the zinc finger DNA-binding domain of the GLI3 protein within the proband and all affected family members. Remarkably, the variant was absent in unaffected individuals within the pedigree, underscoring its association with the polydactyly phenotype. Computational analyses revealed that GLI3 p.Gln494His impacts a residue that is highly conserved across species. CONCLUSION: The GLI3 zinc finger DNA-binding region is an essential part of the Sonic hedgehog signaling pathway, orchestrating crucial aspects of embryonic development through the regulation of target gene expression. This novel finding not only contributes valuable insights into the molecular pathways governing polydactyly during embryonic development but also has the potential to enhance diagnostic and screening capabilities for this condition in clinical settings.

TBX3 is essential for establishment of the posterior boundary of anterior genes and upregulation of posterior genes together with HAND2 during the onset of limb bud development.

During limb bud formation, axis polarities are established as evidenced by the spatially restricted expression of key regulator genes. In particular, the mutually antagonistic interaction between the GLI3 repressor and HAND2 results in distinct and non-overlapping anterior-distal Gli3 and posterior Hand2 expression domains. This is a hallmark of the establishment of antero-posterior limb axis polarity, together with spatially restricted expression of homeodomain and other transcriptional regulators. Here, we show that TBX3 is required for establishment of the posterior expression boundary of anterior genes in mouse limb buds. ChIP-seq and differential gene expression analysis of wild-type and mutant limb buds identifies TBX3-specific and shared TBX3-HAND2 target genes. High sensitivity fluorescent whole-mount in situ hybridisation shows that the posterior expression boundaries of anterior genes are positioned by TBX3-mediated repression, which excludes anterior genes such as Gli3, Alx4, Hand1 and Irx3/5 from the posterior limb bud mesenchyme. This exclusion delineates the posterior mesenchymal territory competent to establish the Shh-expressing limb bud organiser. In turn, HAND2 is required for Shh activation and cooperates with TBX3 to upregulate shared posterior identity target genes in early limb buds.

Distinct expression patterns of Hedgehog signaling components in mouse gustatory system during postnatal tongue development and adult homeostasis.

The Hedgehog (HH) pathway regulates embryonic development of anterior tongue taste fungiform papilla (FP) and the posterior circumvallate (CVP) and foliate (FOP) taste papillae. HH signaling also mediates taste organ maintenance and regeneration in adults. However, there are knowledge gaps in HH pathway component expression during postnatal taste organ differentiation and maturation. Importantly, the HH transcriptional effectors GLI1, GLI2 and GLI3 have not been investigated in early postnatal stages; the HH receptors PTCH1, GAS1, CDON and HHIP, required to either drive HH pathway activation or antagonism, also remain unexplored. Using lacZ reporter mouse models, we mapped expression of the HH ligand SHH, HH receptors, and GLI transcription factors in FP, CVP and FOP in early and late postnatal and adult stages. In adults we also studied the soft palate, and the geniculate and trigeminal ganglia, which extend afferent fibers to the anterior tongue. Shh and Gas1 are the only components that were consistently expressed within taste buds of all three papillae and the soft palate. In the first postnatal week, we observed broad expression of HH signaling components in FP and adjacent, non-taste filiform (FILIF) papillae in epithelium or stroma and tongue muscles. Notably, we observed elimination of Gli1 in FILIF and Gas1 in muscles, and downregulation of Ptch1 in lingual epithelium and of Cdon, Gas1 and Hhip in stroma from late postnatal stages. Further, HH receptor expression patterns in CVP and FOP epithelium differed from anterior FP. Among all the components, only known positive regulators of HH signaling, SHH, Ptch1, Gli1 and Gli2, were expressed in the ganglia. Our studies emphasize differential regulation of HH signaling in distinct postnatal developmental periods and in anterior versus posterior taste organs, and lay the foundation for functional studies to understand the roles of numerous HH signaling components in postnatal tongue development.

A Pilot Immunohistochemical Study Identifies Hedgehog Pathway Expression in Sinonasal Adenocarcinoma.

Tumors of the head and neck, more specifically the squamous cell carcinoma, often show upregulation of the Hedgehog signaling pathway. However, almost nothing is known about its role in the sinonasal adenocarcinoma, either in intestinal or non-intestinal subtypes. In this work, we have analyzed immunohistochemical staining of six Hedgehog pathway proteins, sonic Hedgehog (SHH), Indian Hedgehog (IHH), Patched1 (PTCH1), Gli family zinc finger 1 (GLI1), Gli family zinc finger 2 (GLI2), and Gli family zinc finger 3 (GLI3), on 21 samples of sinonasal adenocarcinoma and compared them with six colon adenocarcinoma and three salivary gland tumors, as well as with matching healthy tissue, where available. We have detected GLI2 and PTCH1 in the majority of samples and also GLI1 in a subset of samples, while GLI3 and the ligands SHH and IHH were generally not detected. PTCH1 pattern of staining shows an interesting pattern, where healthy samples are mostly positive in the stromal compartment, while the signal shifts to the tumor compartment in tumors. This, taken together with a stronger signal of GLI2 in tumors compared to non-tumor tissues, suggests that the Hedgehog pathway is indeed activated in sinonasal adenocarcinoma. As Hedgehog pathway inhibitors are being tested in combination with other therapies for head and neck squamous cell carcinoma, this could provide a therapeutic option for patients with sinonasal adenocarcinoma as well.

A conserved molecular logic for neurogenesis to gliogenesis switch in the cerebral cortex.

During development, neural stem cells in the cerebral cortex, also known as radial glial cells (RGCs), generate excitatory neurons, followed by production of cortical macroglia and inhibitory neurons that migrate to the olfactory bulb (OB). Understanding the mechanisms for this lineage switch is fundamental for unraveling how proper numbers of diverse neuronal and glial cell types are controlled. We and others recently showed that Sonic Hedgehog (Shh) signaling promotes the cortical RGC lineage switch to generate cortical oligodendrocytes and OB interneurons. During this process, cortical RGCs generate intermediate progenitor cells that express critical gliogenesis genes Ascl1, Egfr, and Olig2. The increased Ascl1 expression and appearance of Egfr+ and Olig2+ cortical progenitors are concurrent with the switch from excitatory neurogenesis to gliogenesis and OB interneuron neurogenesis in the cortex. While Shh signaling promotes Olig2 expression in the developing spinal cord, the exact mechanism for this transcriptional regulation is not known. Furthermore, the transcriptional regulation of Olig2 and Egfr has not been explored. Here, we show that in cortical progenitor cells, multiple regulatory programs, including Pax6 and Gli3, prevent precocious expression of Olig2, a gene essential for production of cortical oligodendrocytes and astrocytes. We identify multiple enhancers that control Olig2 expression in cortical progenitors and show that the mechanisms for regulating Olig2 expression are conserved between the mouse and human. Our study reveals evolutionarily conserved regulatory logic controlling the lineage switch of cortical neural stem cells.

Variant characterisation and clinical profile in a large cohort of patients with Ellis-van Creveld syndrome and a family with Weyers acrofacial dysostosis.

BACKGROUND: Ellis-van Creveld syndrome (EvC) is a recessive disorder characterised by acromesomelic limb shortening, postaxial polydactyly, nail-teeth dysplasia and congenital cardiac defects, primarily caused by pathogenic variants in EVC or EVC2. Weyers acrofacial dysostosis (WAD) is an ultra-rare dominant condition allelic to EvC. The present work aimed to enhance current knowledge on the clinical manifestations of EvC and WAD and broaden their mutational spectrum. METHODS: We conducted molecular studies in 46 individuals from 43 unrelated families with a preliminary clinical diagnosis of EvC and 3 affected individuals from a family with WAD and retrospectively analysed clinical data. The deleterious effect of selected variants of uncertain significance was evaluated by cellular assays. MAIN RESULTS: We identified pathogenic variants in EVC/EVC2 in affected individuals from 41 of the 43 families with EvC. Patients from each of the two remaining families were found with a homozygous splicing variant in WDR35 and a de novo heterozygous frameshift variant in GLI3, respectively. The phenotype of these patients showed a remarkable overlap with EvC. A novel EVC2 C-terminal truncating variant was identified in the family with WAD. Deep phenotyping of the cohort recapitulated 'classical EvC findings' in the literature and highlighted findings previously undescribed or rarely described as part of EvC. CONCLUSIONS: This study presents the largest cohort of living patients with EvC to date, contributing to better understanding of the full clinical spectrum of EvC. We also provide comprehensive information on the EVC/EVC2 mutational landscape and add GLI3 to the list of genes associated with EvC-like phenotypes.

Positive correlation between the nuclear expression of GPER and pGLI3 in prostate cancer tissues from patients with different Gleason scores.

Prostate cancer (PCa) is the most prevalent cause of death in the male population worldwide. The G Protein-Coupled Estrogen Receptor (GPER) has been gaining relevance in the development of PCa. Hedgehog (Hh) pathway activation is associated with aggressiveness, metastasis, and relapse in PCa patients. To date, no studies have evaluated the crosstalk between the GPER and the Hh pathway along different group grades in PCa. We conducted an analysis of paraffin-embedded tissues derived from patients with different prognostic grade of PCa using immunohistochemistry. Expression and correlation between GPER and glioma associated oncogene homologue (GLI) transcriptional factors in the parenchyma and stroma of PCa tumors were evaluated. Our results indicate that GPER is highly expressed in the nucleus and increases with higher grade groups. Additionally, GPER's expression correlates with pGLI3 nuclear expression across different grade groups in PCa tissues; however, whether the receptor induces the activation of GLI transcriptional factors, or the latter modulate the expression of GPER is yet to be discovered, as well as the functional consequence of this correlation.

ATRX is a predictive marker for endocrinotherapy and chemotherapy resistance in HER2-/HR+ breast cancer through the regulation of the AR, GLI3 and GATA2 transcriptional network.

Drug resistance in breast cancer (BC) is a clinical challenge. Exploring the mechanism and identifying a precise predictive biomarker for the drug resistance in BC is critical. Three first-line drug (paclitaxel, doxorubicin and tamoxifen) resistance datasets in BC from GEO were merged to obtain 1,461 differentially expressed genes for weighted correlation network analysis, resulting in identifying ATRX as the hub gene. ATRX is a chromatin remodelling protein, therefore, ATRX-associated transcription factors were explored, thereby identifying the network of AR, GLI3 and GATA2. GO and KEGG analyses revealed immunity, transcriptional regulation and endocrinotherapy/chemotherapy resistance were enriched. Moreover, CIBERSORT revealed immunity regulation was inhibited in the resistance group. ssGSEA showed a significantly lower immune status in the ATRX-Low group compared to the ATRX-High group. Furthermore, the peaks of H3K9me3 ChIP-seq on the four genes were higher in normal tissues than in BC tissues. Notably, the frequency of ATRX mutation was higher than BRCA in BC. Moreover, depressed ATRX revealed worse overall survival and disease-free survival in the human epidermal growth factor receptor 2 (HER2)-/hormone receptor (HR)+ BC. Additionally, depressed ATRX predicted poor results for patients who underwent endocrinotherapy or chemotherapy in the HER2-/HR+ BC subgroup. A nomogram based on ATRX, TILs and ER exhibited a significantly accurate survival prediction ability. Importantly, overexpression of ATRX significantly inhibited the IC50 of the three first-line drugs on MCF-7 cell. Thus, ATRX is an efficient predictive biomarker for endocrinotherapy and chemotherapy resistance in HER2-/HR+ BC and acts by suppressing the AR, GLI3 and GATA2 transcriptional network.

The BAF chromatin complex component SMARCC1 does not mediate GLI transcriptional repression of Hedgehog target genes in limb buds.

Transcriptional responses to the Hedgehog (HH) signaling pathway are primarily modulated by GLI repression in the mouse limb. Previous studies suggested a role for the BAF chromatin remodeling complex in mediating GLI repression. Consistent with this possibility, the core BAF complex protein SMARCC1 is present at most active limb enhancers including the majority of GLI enhancers. However, in contrast to GLI repression which reduces chromatin accessibility, SMARCC1 maintains chromatin accessibility at most enhancers, including those bound by GLI. Moreover, SMARCC1 binding at GLI-regulated enhancers occurs independently of GLI3. Consistent with previous studies, some individual GLI target genes are mis-regulated in Smarcc1 conditional knockouts, though most GLI target genes are unaffected. Moreover, SMARCC1 is not necessary for mediating constitutive GLI repression in HH mutant limb buds. We conclude that SMARCC1 does not mediate GLI3 repression, which we propose utilizes alternative chromatin remodeling complexes.

Analysis of variant of GLI3 gene in a child featuring autosomal dominant Pallister-Hall syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical and genetic characteristics of a child with Pallister-Hall syndrome (PHS).@*METHODS@#DNA was extracted from peripheral blood sample from the child and subjected to whole exome sequencing. Suspected variants were verified by Sanger sequencing of his family members.@*RESULTS@#Genetic testing revealed that the child has harbored a heterozygous c.3320_3330delGGTACGAGCAG (p.G1107Afs×18) variant of the GLI3 gene. Neither parent was found to carry the same variant.@*CONCLUSION@#The c.3320_3330delGGTACGAGCAG (p.G1107Afs×18) frameshift variant of the GLI3 gene probably underlay the pathogenesis of PHS in this child. Genetic testing should be considered for patients featuring hypothalamic hamartoma and central polydactyly.

A study on etiology of incontinence in double knockout mouse model.

INTRODUCTION AND OBJECTIVE: Stress urinary incontinence is of concern in both pediatric and adult population. Double mutant GLI family zinc finger Gli2+/-; Gli3Δ699/+ murine model of stress incontinence has been recently developed as a reliable model which does not require surgical manipulation to create incontinence and is shown to survive to adulthood. The aim of this study was to establish the etiology of incontinence in the double mutant Gli2+/-; Gli3Δ699/+ mice. STUDY DESIGN: We used 13 cluster of differentiation 1 (CD-1) mice (7-9 weeks) for demonstration of histology of the bladder and urethra. There were 3 Wild Gli2+/- females, 2 Wild Gli2+/- males, 4 Gli2+/-;Gli3Δ699/+ females and 4 Gli2+/-;Gli3Δ699/+ males. The Wild Gli2+/- mice served as the control group and Gli2+/-;Gli3Δ699/+ mice served as the test group. Additionally, eight 16.5 days mice (2 each of Wild Gli2+/- females, Wild Gli2+/- males, double knockout (DKO) Gli2+/-;Gli3Δ699/+ females and Gli2+/-;Gli3Δ699/+ males) were used to assess the histology of the spinal cord. The gross appearance of bladder and urethra was studied using ink injection assays. Immunohistochemistry was done for smooth muscle actin and cytokeratin. RESULTS: Gross and histologic appearance confirmed the previously reported widening of bladder outlet and hypoplasia of smooth muscles in female urethra and also established them in the male urethra of Gli2+/-;Gli3Δ699/+ mice compared to Gli2+/- mice. The double knockout mice were smaller than the Gli2 mice (5.2 vs 6.1 cm, p = 0.002). Immunohistochemistry demonstrated epithelial hyperplasia and smooth muscle hypoplasia. Additionally, there was prostatic hypoplasia in the Gli2+/-;Gli3Δ699/+ male mice. The spinal cord length for body size appeared comparable between the Gli2+/- and Gli2+/-;Gli3Δ699/+ mice but histological evaluation revealed abnormal development of the caudal end of the vertebral body with premature termination of the spinal cord (Figure). DISCUSSION: The histological changes in the bladder neck and urethra were consistent to those previously reported. While previous report described the findings in female mice only, we confirmed that these findings are also present in males as well as prostatic hypoplasia, a possible additional factor leading to stress incontinence. The most important finding in the present study however, was the detection of premature termination of spinal cord in the DKO Gli2+/-; Gli3Δ699/+ mice which has not been reported previously and is likely a major contributor to incontinence in this model. CONCLUSION: The incontinence in male as well as female Gli2+/-; Gli3Δ699/+ mice is due to both myogenic and neurogenic involvement. These double knockout mice are a valuable model of stress incontinence related to neurogenic bladder due to low outlet resistance.

[Analysis of variant of GLI3 gene in a child featuring autosomal dominant Pallister-Hall syndrome].

OBJECTIVE: To explore the clinical and genetic characteristics of a child with Pallister-Hall syndrome (PHS). METHODS: DNA was extracted from peripheral blood sample from the child and subjected to whole exome sequencing. Suspected variants were verified by Sanger sequencing of his family members. RESULTS: Genetic testing revealed that the child has harbored a heterozygous c.3320_3330delGGTACGAGCAG (p.G1107Afs×18) variant of the GLI3 gene. Neither parent was found to carry the same variant. CONCLUSION: The c.3320_3330delGGTACGAGCAG (p.G1107Afs×18) frameshift variant of the GLI3 gene probably underlay the pathogenesis of PHS in this child. Genetic testing should be considered for patients featuring hypothalamic hamartoma and central polydactyly.

Conclusion of diagnostic odysseys due to inversions disrupting GLI3 and FBN1.

Many genetic testing methodologies are biased towards picking up structural variants (SVs) that alter copy number. Copy-neutral rearrangements such as inversions are therefore likely to suffer from underascertainment. In this study, manual review prompted by a virtual multidisciplinary team meeting and subsequent bioinformatic prioritisation of data from the 100K Genomes Project was performed across 43 genes linked to well-characterised skeletal disorders. Ten individuals from three independent families were found to harbour diagnostic inversions. In two families, inverted segments of 1.2/14.8 Mb unequivocally disrupted GLI3 and segregated with skeletal features consistent with Greig cephalopolysyndactyly syndrome. For one family, phenotypic blending was due to the opposing breakpoint lying ~45 kb from HOXA13 In the third family, long suspected to have Marfan syndrome, a 2.0 Mb inversion disrupting FBN1 was identified. These findings resolved lengthy diagnostic odysseys of 9-20 years and highlight the importance of direct interaction between clinicians and data-analysts. These exemplars of a rare mutational class inform future SV prioritisation strategies within the NHS Genomic Medicine Service and similar genome sequencing initiatives. In over 30 years since these two disease-gene associations were identified, large inversions have yet to be described and so our results extend the mutational spectra linked to these conditions.

Pallister-Hall syndrome, GLI3, and kidney malformation.

Pallister-Hall syndrome (PHS) is a rare autosomal dominant disease diagnosed by the presence of hypothalamic hamartoma, mesoaxial polydactyly and a truncating variant in the middle third of the GLI-Kruppel family member 3 (GLI3) gene. PHS may also include a wide range of clinical phenotypes affecting multiple organ systems including congenital anomalies of the kidney and urinary tract (CAKUT). The observed clinical phenotypes are consistent with the essential role of GLI3, a transcriptional effector in the hedgehog (Hh) signaling pathway, in organogenesis. However, the mechanisms by which truncation of GLI3 in PHS results in such a variety of clinical phenotypes with variable severity, even within the same organ, remain unclear. In this study we focus on presentation of CAKUT in PHS. A systematic analysis of reported PHS patients (n = 78) revealed a prevalence of 26.9% (21/78) of CAKUT. Hypoplasia (± dysplasia) and agenesis were the two main types of CAKUT; bilateral and unilateral CAKUT were reported with equal frequency. Examination of clinical phenotypes with CAKUT revealed a significant association between CAKUT and craniofacial defects, bifid epiglottis and a Disorder of Sex Development, specifically affecting external genitalia. Lastly, we determined that PHS patients with CAKUT predominately had substitution type variants (as opposed to deletion type variants in non-CAKUT PHS patients) in the middle third of the GLI3 gene. These results provide a foundation for future work aimed at uncovering the molecular mechanisms by which variant GLI3 result in the wide range and severity of clinical features observed in PHS.

A novel mechanism of regulation of the oncogenic transcription factor GLI3 by toll-like receptor signaling.

The transcription factor GLI3 is a member of the GLI family and has been shown to be regulated by canonical hedgehog (HH) signaling through smoothened (SMO). Little is known about SMO-independent regulation of GLI3. Here, we identify TLR signaling as a novel pathway regulating GLI3 expression. We show that GLI3 expression is induced by LPS/TLR4 in human monocyte cell lines and peripheral blood CD14+ cells. Further analysis identified TRIF, but not MyD88, signaling as the adapter used by TLR4 to regulate GLI3. Using pharmacological and genetic tools, we identified IRF3 as the transcription factor regulating GLI3 downstream of TRIF. Furthermore, using additional TLR ligands that signal through TRIF such as the TLR4 ligand, MPLA and the TLR3 ligand, Poly(I:C), we confirm the role of TRIF-IRF3 in the regulation of GLI3. We found that IRF3 directly binds to the GLI3 promoter region and this binding was increased upon stimulation of TRIF-IRF3 with Poly(I:C). Furthermore, using Irf3 -/- MEFs, we found that Poly(I:C) stimulation no longer induced GLI3 expression. Finally, using macrophages from mice lacking Gli3 expression in myeloid cells (M-Gli3-/- ), we found that in the absence of Gli3, LPS stimulated macrophages secrete less CCL2 and TNF-α compared with macrophages from wild-type (WT) mice. Taken together, these results identify a novel TLR-TRIF-IRF3 pathway that regulates the expression of GLI3 that regulates inflammatory cytokines and expands our understanding of the non-canonical signaling pathways involved in the regulation of GLI transcription factors.