A cell-autonomous role for primary cilium-mediated signaling in long-range commissural axon guidance.

Ciliopathies are characterized by the absence or dysfunction of primary cilia. Despite the fact that cognitive impairments are a common feature of ciliopathies, how cilia dysfunction affects neuronal development has not been characterized in detail. Here, we show that primary cilium-mediated signaling is required cell-autonomously by neurons during neural circuit formation. In particular, a functional primary cilium is crucial during axonal pathfinding for the switch in responsiveness of axons at a choice point, or intermediate target. Utilizing different animal models and in vivo, ex vivo, as well as in vitro experiments, we provide evidence for a critical role of primary cilium-mediated signaling in long-range axon guidance. The primary cilium on the cell body of commissural neurons transduces long-range guidance signals sensed by growth cones navigating an intermediate target. In extension of our finding that Shh is required for the rostral turn of post-crossing commissural axons, we suggest a model implicating the primary cilium in Shh signaling upstream of a transcriptional change of axon guidance receptors, which in turn mediate the repulsive response to floorplate-derived Shh shown by post-crossing commissural axons.

Liver Extracellular Vesicles and Particles Enriched ß-Sitosterol Effectively Promote Liver Regeneration in Mice.

Background: The liver's regenerative capacity allows it to repair itself after injury. Extracellular vesicles and particles (EVPs) in the liver's interstitial space are crucial for signal transduction, metabolism, and immune regulation. Understanding the role and mechanism of liver-derived EVPs in regeneration is significant, particularly after partial hepatectomy, where the mechanisms remain unclear. Methods: A 70% hepatectomy model was established in mice, and EVPs were isolated and characterized using electron microscopy, nanocharacterization, and Western blot analysis. Combined metabolomic and transcriptomic analyses revealed ß-sitosterol enrichment in EVPs and activation of the Hedgehog signaling pathway during regeneration. The role of ß-sitosterol in EVPs on the Hedgehog pathway and its targets were identified using qRT-PCR, Western blot analysis. The regulation of carnitine synthesis by this pathway was determined using a dual luciferase assay. The effect of a ß-sitosterol diet on liver regeneration was verified in mice. Results: After 70% hepatectomy, the liver successfully regenerated without liver failure or death. At 24 hours post-surgery, tissue staining showed transient regeneration-associated steatosis (TRAS), with increased Ki67 positivity at 48 hours. EVPs displayed a spherical lipid bilayer structure with particle sizes of 70-130 nm. CD9, CD63, and CD81 in liver-derived EVPs were confirmed. Transcriptomic and metabolomic analyses showed EVPs supplementation significantly promoted carnitine synthesis and fatty acid oxidation. Tissue staining confirmed accelerated TRAS resolution and enhanced liver regeneration with EVP supplementation. Mass spectrometry identified ß-sitosterol in EVPs, which binds to Smo protein, activating the Hedgehog pathway. This led to the nuclear transport of Gli3, stimulating Setd5 transcription and inducing carnitine synthesis, thereby accelerating fatty acid oxidation. Mice with increased ß-sitosterol intake showed faster TRAS resolution and liver regeneration compared to controls. Conclusion: Liver-derived EVPs promote regeneration after partial hepatectomy. ß-sitosterol from EVPs accelerates fatty acid oxidation and promotes liver regeneration by activating Hedgehog signaling pathway.

Mesenchymal stem cells-derived exosomes alleviate liver fibrosis by targeting Hedgehog/SMO signaling.

BACKGROUND & AIMS: Despite increasing knowledge regarding the cellular and molecular mechanisms of liver fibrogenesis, there is currently no approved drug for the treatment of liver fibrosis. Mesenchymal stem cells (MSCs) are multipotent progenitor cells representing an attractive therapeutic tool for tissue damage and inflammation. This study was designed to determine the protective effect and underlying mechanism of human umbilical cord-derived MSCs (UC-MSCs) on thioacetamide-induced liver fibrosis. METHODS: Liver fibrosis was induced in mice by intraperitoneal injection of thioacetamide (TAA). Some mice were then given injection of UC-MSCs or UC-MSCs-derived exosomes (UC-MSCs-Exo) via the tail vein. Liver tissues were collected for histologic analysis. RESULTS: We found that administration of UC-MSCs significantly reduced serum alanine aminotransferase and aspartate aminotransferase levels, and attenuated hepatic inflammation and fibrosis. Moreover, the therapeutic effect of UC-MSCs-derived exosomes was similar to that of UC-MSCs. Intriguingly, UC-MSCs-Exo treatment downregulated the expression of smoothened (SMO), a fundamental component of Hedgehog signaling which plays a critical role in fibrogenesis, and subsequently inhibited the activation of hepatic stellate cells, a central driver of fibrosis in experimental and human liver injury. Furthermore, the anti-inflammatory and anti-fibrotic effects of UCMSCs- Exo was reversed by the SMO agonist SAG treatment in mice. CONCLUSION: Our findings suggest that UC-MSCs-Exo exert therapeutic effects on liver fibrosis, at least in part, through inhibiting the Hedgehog/SMO signaling pathway.

Benzaldehyde stimulates autophagy via the sonic hedgehog signaling pathway in mouse brain astrocytes after treatment with Angiostrongylus cantonensis excretory-secretory products.

Autophagy is a vital cellular process responsible for digesting various cytoplasmic organelles. This process plays a crucial role in maintaining cell survival and homeostasis, especially under conditions that cause nutrient deficiency, cellular damage, and oxidative stress. Neuroangiostrongyliasis is an infection caused by the parasitic nematode Angiostrongylus cantonensis and is considered as an emerging disease in many parts of the world. However, effective therapeutic strategies for neuroangiostrongyliasis still need to be further developed. In this study, we investigated the effects of benzaldehyde treatment on autophagy and sonic hedgehog (Shh) signaling in A. cantonensis-infected mice and its mechanisms. First, we found autophagosome generation in the central nervous system after A. cantonensis infection. Next, benzaldehyde combined with albendazole treatment reduced eosinophilic meningitis and upregulated the expression of Shh signaling- and autophagy-related molecules in A. cantonensis-infected mouse brains. In vitro experiments demonstrated that benzaldehyde could induce autophagy via the Shh signaling pathway in A. cantonensis excretory-secretory products (ESPs)-treated mouse astrocytes. Finally, benzaldehyde treatment also decreased lipid droplet accumulation and increased cholesterol production by activating the Shh pathway after ESPs treatment. In conclusion, these findings suggested that benzaldehyde treatment could alleviate brain damage by stimulating autophagy generation through the Shh signaling pathway.

Conditioned Medium From Reactive Astrocytes Inhibits Proliferation, Resistance, and Migration of p53-Mutant Glioblastoma Spheroid Through GLI-1 Downregulation.

Glioblastoma (GBM) aggressiveness is partly driven by the reactivation of signaling pathways such as Sonic hedgehog (SHH) and the interaction with its microenvironment. SHH pathway activation is one of the phenomena behind the glial transformation in response to tumor growth. The reactivation of the SHH signaling cascade during GBM-astrocyte interaction is highly relevant to understanding the mechanisms used by the tumor to modulate the adjacent stroma. The role of reactive astrocytes considering SHH signaling during GBM progression is investigated using a 3D in vitro model. T98G GBM spheroids displayed significant downregulation of SHH (61.4 ± 9.3%), GLI-1 (6.5 ± 3.7%), Ki-67 (33.7 ± 8.1%), and mutant MTp53 (21.3 ± 10.6%) compared to the CONTROL group when incubated with conditioned medium of reactive astrocytes (CM-AST). The SHH pathway inhibitor, GANT-61, significantly reduced previous markers (SHH = 43.0 ± 12.1%; GLI-1 = 9.5 ± 3.4%; Ki-67 = 31.9 ± 4.6%; MTp53 = 6.5 ± 7.5%) compared to the CONTROL, and a synergistic effect could be observed between GANT-61 and CM-AST. The volume (2.0 ± 0.2 × 107 µm³), cell viability (80.4 ± 3.2%), and migration (41 ± 10%) of GBM spheroids were significantly reduced in the presence of GANT-61 and CM-AST when compared to CM-AST after 72 h (volume = 2.3 ± 0.4 × 107 µm³; viability = 92.2 ± 6.5%; migration = 102.5 ± 14.6%). Results demonstrated that factors released by reactive astrocytes promoted a neuroprotective effect preventing GBM progression using a 3D in vitro model potentiated by SHH pathway inhibition.

Sonic hedgehog expression in steatohepatitic hepatocellular carcinoma and its clinicopathological significance.

Hedgehog (Hh) signaling pathway dysregulation is involved in the pathogenesis of metabolic dysfunction-associated steatohepatitis, and the sonic Hh (SHh) protein, a pivotal molecule in the Hh pathway, is expressed in ballooned hepatocytes. The present study aimed to investigate the clinicopathological significance of SHh expression in steatohepatitic hepatocellular carcinoma (SH-HCC). Reverse transcription-quantitative polymerase chain reaction and immunohistochemistry were performed to examine SHh gene and SHh protein expression in SH-HCC. Additionally, patients with conventional HCC (C-HCC) were included in the control group. Comparisons of patient and tumor characteristics were also performed. The prevalence of SH-HCC was 3% in the whole cohort, and it was significantly associated with a high prevalence of diabetes mellitus. SHh mRNA was detected in all patients with SH-HCC, but not in 23% of patients with C-HCC. Notably, SHh mRNA expression was not significantly different between patients with SH-HCC and those with C-HCC; however, high SHh protein expression was significantly more frequent in SH-HCC patients than in those with C-HCC. Although the prognosis was not significantly different between the SH-HCC and C-HCC groups, high SHh protein expression was an independent poor prognostic factor for HCC. In conclusion, SHh could potentially serve as a therapeutic target for patients with HCC.

Trichophyton erinacei infection in humans: a case report and a literature review.

BACKGROUND: Trichophyton (T.) erinacei is a rare but emerging zoonotic dermatophyte that is rarely isolated as a human pathogen, with only a few cases extensively described in the literature. PATIENTS AND METHODS: We conducted a systematic search to identify eligible articles reporting demographics, clinical characteristics, and the therapeutic approach regarding T. erinacei infection in humans. RESULTS: 168 patients affected by T. erinacei were reported in the international literature between inception and November 2023. Only 56 cases (32.1%) were fully described. The median age at diagnosis was 26 years, the female/male ratio was around 2:1. The main source of the disease was the hedgehog. The infection presented with a combination of erythema, scaly plaques, pustules, papules, vesicles, oedema, and erosion; the most common locations were the hands and the head. The most frequently conducted examination was fungal culture, but gene sequencing and mass spectrometry improved both speed and precision in the most recent diagnostic course. Topical clotrimazole and systemic terbinafine were the most chosen treatment. CONCLUSIONS: Trichophyton erinacei should be considered in patients with erythematous scaly patches and recent contact with hedgehogs. Terbinafine should be considered as a first-line effective treatment, griseofulvin and azoles could be considered valid alternatives.

BCAA-producing Clostridium symbiosum promotes colorectal tumorigenesis through the modulation of host cholesterol metabolism.

Identification of potential bacterial players in colorectal tumorigenesis has been a focus of intense research. Herein, we find that Clostridium symbiosum (C. symbiosum) is selectively enriched in tumor tissues of patients with colorectal cancer (CRC) and associated with higher colorectal adenoma recurrence after endoscopic polypectomy. The tumorigenic effect of C. symbiosum is observed in multiple murine models. Single-cell transcriptome profiling along with functional assays demonstrates that C. symbiosum promotes the proliferation of colonic stem cells and enhances cancer stemness. Mechanistically, C. symbiosum intensifies cellular cholesterol synthesis by producing branched-chain amino acids (BCAAs), which sequentially activates Sonic hedgehog signaling. Low dietary BCAA intake or blockade of cholesterol synthesis by statins could partially abrogate the C. symbiosum-induced cell proliferation in vivo and in vitro. Collectively, we reveal C. symbiosum as a bacterial driver of colorectal tumorigenesis, thus identifying a potential target in CRC prediction, prevention, and treatment.

Dysembryogenetic Pathogenesis of Basal Cell Carcinoma: The Evidence to Date.

The Basal Cell Carcinoma (BCC) is a sort of unique tumour due to its combined peculiar histological features and clinical behaviour, such as the constant binary involvement of the epithelium and the stroma, the virtual absence of metastases and the predilection of specific anatomical sites for both onset and spread. A potential correlation between the onset of BCC and a dysembryogenetic process has long been hypothesised. A selective investigation of PubMed-indexed publications supporting this theory retrieved 64 selected articles published between 1901 and 2024. From our analysis of the literature review, five main research domains on the dysembryogenetic pathogenesis of BCC were identified: (1) The correlation between the topographic distribution of BCC and the macroscopic embryology, (2) the correlation between BCC and the microscopic embryology, (3) the genetic BCC, (4) the correlation between BCC and the hair follicle and (5) the correlation between BCC and the molecular embryology with a specific focus on the Hedgehog signalling pathway. A large amount of data from microscopic and molecular research consistently supports the hypothesis of a dysembryogenetic pathogenesis of BCC. Such evidence is promoting advances in the clinical management of this disease, with innovative targeted molecular therapies on an immune modulating basis being developed.

An Epilepsy-Associated CILK1 Variant Compromises KATNIP Regulation and Impairs Primary Cilia and Hedgehog Signaling.

Mutations in human CILK1 (ciliogenesis associated kinase 1) are linked to ciliopathies and epilepsy. Homozygous point and nonsense mutations that extinguish kinase activity impair primary cilia function, whereas mutations outside the kinase domain are not well understood. Here, we produced a knock-in mouse equivalent to the human CILK1 A615T variant identified in juvenile myoclonic epilepsy (JME). This residue is in the intrinsically disordered C-terminal region of CILK1 separate from the kinase domain. Mouse embryo fibroblasts (MEFs) with either heterozygous or homozygous A612T mutant alleles exhibited a higher ciliation rate, shorter individual cilia, and upregulation of ciliary Hedgehog signaling. Thus, a single A612T mutant allele was sufficient to impair primary cilia and ciliary signaling in MEFs. Gene expression profiles of wild-type versus mutant MEFs revealed profound changes in cilia-related molecular functions and biological processes. The CILK1 A615T mutant protein was not increased to the same level as the wild-type protein when co-expressed with scaffold protein KATNIP (katanin-interacting protein). Our data show that KATNIP regulation of a JME-associated single-residue variant of CILK1 is compromised, and this impairs the maintenance of primary cilia and Hedgehog signaling.

PP2A phosphatase regulatory subunit PPP2R3C is a new positive regulator of the hedgehog signaling pathway.

Cellular signaling pathways rely on posttranslational modifications (PTMs) to finely regulate protein functions, particularly transcription factors. The Hedgehog (Hh) signaling cascade, crucial for embryonic development and tissue homeostasis, is susceptible to aberrations that lead to developmental anomalies and various cancers. At the core of Hh signaling are Gli proteins, whose dynamic balance between activator (GliA) and repressor (GliR) states shapes cellular outcomes. Phosphorylation, orchestrated by multiple kinases, is pivotal in regulating Gli activity. While kinases in this context have been extensively studied, the role of protein phosphatases, particularly Protein Phosphatase 2A (PP2A), remains less explored. This study unveils a novel role for the B″gamma subunit of PP2A, PPP2R3C, in Hh signaling regulation. PPP2R3C interacts with Gli proteins, and its disruption reduces Hedgehog pathway activity as measured by reduced expression of Gli1/2 and Hh target genes upon Hh signaling activation, and reduced growth of a Hh signaling-dependent medulloblastoma cell line. Moreover, we establish an antagonistic connection between PPP2R3C and MEKK1 kinase in Gli protein phosphorylation, underscoring the intricate interplay between kinases and phosphatases in Hh signaling pathway. This study sheds light on the previously understudied role of protein phosphatases in Hh signaling and provides insights into their significance in cellular regulation.

Hedgehog components are overexpressed in a series of liver cancer cases.

Liver cancers, including hepatocellular carcinoma (HCC), are the sixth most common cancer and the third leading cause of cancer-related death worldwide, representing a global public health problem. This study evaluated nine patients with HCC. Six of the cases involved hepatic explants, and three involved hepatic segmentectomy for tumor resection. Eight out of nine tumors were HCC, with one being a combined hepatocellular-cholangiocarcinoma tumor. Conventional markers of hepatocellular differentiation (Hep Par-1, arginase, pCEA, and glutamine synthetase) were positive in all patients, while markers of hepatic precursor cells (CK19, CK7, EpCAM, and CD56) were negative in most patients, and when positive, they were detected in small, isolated foci. Based on in silico analysis of HCC tumors from The Cancer Genome Atlas database, we found that Hedgehog (HH) pathway components (GLI1, GLI2, GLI3 and GAS1) have high connectivity values (module membership > 0.7) and are strongly correlated with each other and with other genes in biologically relevant modules for HCC. We further validated this finding by analyzing the gene expression of HH components (PTCH1, GLI1, GLI2 and GLI3) in our samples through qPCR, as well as by immunohistochemical analysis. Additionally, we conducted a chemosensitivity analysis using primary HCC cultures treated with a panel of 18 drugs that affect the HH pathway and/or HCC. Most HCC samples were sensitive to sunitinib. Our results offer a comprehensive view of the molecular landscape of HCC, highlighting the significance of the HH pathway and providing insight into focused treatments for HCC.

An "R-spondin code" for multimodal signaling ON-OFF states.

R-spondins (RSPOs) are a family of secreted proteins and stem cell growth factors that are potent co-activators of Wnt signaling. Recently, RSPO2 and RSPO3 were shown to be multifunctional, not only amplifying Wnt- but also binding BMP- and FGF receptors to downregulate signaling. The common mechanism underlying these diverse functions is that RSPO2 and RSPO3 act as "endocytosers" that link transmembrane proteins to ZNRF3/RNF43 E3 ligases and trigger target internalization. Thus, RSPOs are natural protein targeting chimeras for cell surface proteins. Conducting data mining and cell surface binding assays we report additional candidate RSPO targets, including SMO, PTC1,2, LGI1, ROBO4, and PTPR(F/S). We propose that there is an "R-spondin code" that imparts combinatorial signaling ON-OFF states of multiple growth factors. This code involves the modular RSPO domains, notably distinct motifs in the divergent RSPO-TSP1 domains to mediate target interaction and internalization. The RSPO code offers a novel framework for the understanding how diverse signaling pathways may be coordinately regulated in development and disease.

Single-cell RNA-sequencing Analysis Reveals the Promoting Role of the Hedgehog Pathway in Epithelial Cells during Cervical Cancer Progression.

AIM: This study explored the role of the Hedgehog pathway in epithelial cells during cervical cancer [CC] progression, providing new insights for improving current CC treatment. BACKGROUND: Abnormal activation of the Hedgehog signaling pathway is associated with the malignant transformation of CC epithelial cells. Single-cell atlas of CC and the role of Hedgehog pathway in epithelial cells during CC progression remain to be explored. OBJECTIVE: To comprehensively analyze the mechanism of Hedgehog pathway activation in CC epithelial cells and its impact on tumor progression by applying single-cell RNA sequencing [scRNA-seq] analysis. METHODS: The scRNA-seq data were acquired from the Gene Expression Omnibus [GEO] database and then processed with the Seurat package. FindNeighbors and Find- Clusters functions were applied to cluster the cells. The CellMarker database was used for subgroup annotation. Differentially expressed genes [DEGs] in each cell subgroup were filtered by FindAllMarkers function. Biological function analysis for the gene set of interest was performed using Clusterprofiler package. AUCell function was employed to calculate the score of the Hedgehog pathway. The differentiation trajectory in epithelial cell subtypes was generated by performing Pseudotime analysis. Finally, protein-protein network [PPI] was used to investigate the interactions between the Hedgehog pathway and other pathways enriched in the gene set of interest. RESULTS: A total of 9 major cell subpopulations were classified and the proportion of epithelial cells was the highest in CC samples. Further analysis revealed that the Hedgehog pathway was abnormally activated in STYK1+ and TP73+ epithelial cell subtypes. Pseudo-time trajectory analysis showed that the differentiation trajectory of STYK1+ epithelial cells gradually transformed into defense-to-virus cells or into proliferation cells, while TP73+ epithelial cells eventually differentiated into two branches of response to estrogen and virus-induced proliferation. PPI analysis showed that the Hedgehog pathway was involved in the proliferation and viral process of epithelial cells in CC. CONCLUSION: The current study comprehensively analyzed the features of CC samples and differentiation trajectories of epithelial cell subtypes, as well as the role of the Hedgehog pathway in epithelial cells during CC progression. More importantly, effective target genes were discovered for the molecular diagnosis and precise treatment of CC.

Exosomal LINC00958 maintains ovarian cancer cell stemness and induces M2 macrophage polarization via Hedgehog signaling pathway and GLI1 protein.

Long non-coding RNA (lncRNA) LINC00958 has been reported to promote many gynecological cancers, but its detailed function in OC remains unclear. Cancer stem cells (CSCs) and tumor-associated macrophages (TAMs) have been reported to participate in the occurrence and metastasis of cancers. We want to explore the effects of exosomal LINC00958 on cell stemness and macrophage polarization in OC. LINC00958 expression was first verified in OC cells and its function on cell stemness was verified by subcellular fractionation analysis, sphere formation assay and so on. Exosomal LINC00958 was secreted from OC cells and the model of M2 macrophage polarization was established to further verify the impact of exosomal LINC00958 on the cell stemness and macrophage polarization of OC cells using several mechanism experiments including flow cytometry, RNA pulldown, luciferase reporter assays and so on. LINC00958 was up-regulated in OC cells and exosomal LINC00958 enhanced the stem cell-like properties of OC cells and M2 macrophage polarization. Furthermore, LINC00958 combined with glioma-associated oncogene homolog 1 (GLI1) to activate Hedgehog pathway, thereby promoting M2 polarization. Exosomal LINC00958 maintained OC cell stemness and induced M2 polarization via the Hedgehog signaling pathway.

Diffusion barriers imposed by tissue topology shape Hedgehog morphogen gradients.

Animals use a small number of morphogens to pattern tissues, but it is unclear how evolution modulates morphogen signaling range to match tissues of varying sizes. Here, we used single-molecule imaging in reconstituted morphogen gradients and in tissue explants to determine that Hedgehog diffused extracellularly as a monomer, and rapidly transitioned between membrane-confined and -unconfined states. Unexpectedly, the vertebrate-specific protein SCUBE1 expanded Hedgehog gradients by accelerating the transition rates between states without affecting the relative abundance of molecules in each state. This observation could not be explained under existing models of morphogen diffusion. Instead, we developed a topology-limited diffusion model in which cell-cell gaps create diffusion barriers, which morphogens can only overcome by passing through a membrane-unconfined state. Under this model, SCUBE1 promoted Hedgehog secretion and diffusion by allowing it to transiently overcome diffusion barriers. This multiscale understanding of morphogen gradient formation unified prior models and identified knobs that nature can use to tune morphogen gradient sizes across tissues and organisms.

Desert Hedgehog Down-regulation Mediates Inhibition of Proliferation by γ-Glutamylcyclotransferase Knockdown in Murine Glioblastoma Stem Cells.

BACKGROUND/AIM: Glioblastoma is the most frequent type of adult-onset malignant brain tumor and has a very poor prognosis. Glioblastoma stem cells have been shown to be one of the mechanisms by which glioblastoma acquires therapy resistance. Therefore, there is a need to establish novel therapeutic strategies useful for inhibiting this cell population. γ-Glutamylcyclotransferase (GGCT) is an enzyme involved in the synthesis and metabolism of glutathione, which is highly expressed in a wide range of cancer types, including glioblastoma, and inhibition of its expression has been reported to have antitumor effects on various cancer types. The aim of this study was to clarify the function of GGCT in glioblastoma stem cells. MATERIALS AND METHODS: We searched for pathways affected by GGCT overexpression in mouse embryonic fibroblasts NIH-3T3 by comprehensive gene expression analysis. Knockdown of GGCT and overexpression of desert hedgehog (DHH), a representative ligand of the pathway, were performed in glioblastoma stem cells derived from a mouse glioblastoma model. RESULTS: GGCT overexpression activated the hedgehog pathway. Knockdown of GGCT inhibited proliferation of glioblastoma stem cells and reduced expression of DHH and the downstream target GLI family zinc finger 1 (GLI1). DHH overexpression significantly restored the growth-suppressive effect of GGCT knockdown. CONCLUSION: High GGCT expression is important for expression of DHH and activation of the hedgehog pathway, which is required to maintain glioblastoma stem cell proliferation. Therefore, inhibition of GGCT function may be useful in suppressing stemness of glioblastoma stem cells accompanied by activation of the hedgehog pathway.

Identification of small molecule antagonists of sonic hedgehog/heparin binding with activity in hedgehog functional assays.

Sonic hedgehog (Shh) is a morphogen with important roles in embryonic development and in the development of a number of cancers. Its activity is modulated by interactions with binding partners and co-receptors including heparin and heparin sulfate proteoglycans (HSPG). To identify antagonists of Shh/heparin binding, a diverse collection of 34,560 chemicals was screened in single point 384-well format. We identified and confirmed twenty six novel small molecule antagonists with diverse structures including four scaffolds that gave rise to multiple hits. Nineteen of the confirmed hits blocked binding of the N-terminal fragment of Shh (ShhN) to heparin with IC50 values < 50 µM. In the Shh-responsive C3H10T1/2 cell model, four of the compounds demonstrated the ability to block ShhN-induced alkaline phosphatase activity. To demonstrate a direct and selective effect on ShhN ligand mediated activity, two of the compounds were able to block induction of Gli1 mRNA, a primary downstream marker for Shh signaling activity, in Shh-mediated but not Smoothened agonist (SAG)-mediated C3H10T1/2 cells. Direct binding of the two compounds to ShhN was confirmed by thermal shift assay and molecular docking simulations, with both compounds docking with the N-terminal heparin binding domain of Shh. Overall, our findings indicate that small molecule compounds that block ShhN binding to heparin and act to inhibit Shh mediated activity in vitro can be identified. We propose that the interaction between Shh and HSPGs provides a novel target for identifying small molecules that bind Shh, potentially leading to novel tool compounds to probe Shh ligand function.

Loss of primary cilia and dopaminergic neuroprotection in pathogenic LRRK2-driven and idiopathic Parkinson's disease.

Activating leucine-rich repeat kinase 2 (LRRK2) mutations cause Parkinson's and phosphorylation of Rab10 by pathogenic LRRK2 blocks primary ciliogenesis in cultured cells. In the mouse brain, LRRK2 blockade of primary cilia is highly cell type specific: For example, cholinergic interneurons and astrocytes but not medium spiny neurons of the dorsal striatum lose primary cilia in LRRK2-pathway mutant mice. We show here that the cell type specificity of LRRK2-mediated cilia loss is also seen in human postmortem striatum from patients with LRRK2 pathway mutations and idiopathic Parkinson's. Single nucleus RNA sequencing shows that cilia loss in mouse cholinergic interneurons is accompanied by decreased glial-derived neurotrophic factor transcription, decreasing neuroprotection for dopamine neurons. Nevertheless, LRRK2 expression differences cannot explain the unique vulnerability of cholinergic neurons to LRRK2 kinase as much higher LRRK2 expression is seen in medium spiny neurons that have normal cilia. In parallel with decreased striatal dopaminergic neurite density, LRRK2 G2019S neurons show increased autism-linked CNTN5 adhesion protein expression; glial cells show significant loss of ferritin heavy chain. These data strongly suggest that loss of cilia in specific striatal cell types decreases neuroprotection for dopamine neurons in mice and human Parkinson's.

Hypoxia-sonic hedgehog axis as a driver of primitive hematopoiesis development and evolution in cavefish.

The teleost Astyanax mexicanus consists of surface dwelling (surface fish) and cave dwelling (cavefish) forms. Cavefish have evolved in subterranean habitats characterized by reduced oxygen levels (hypoxia) and exhibit a subset of phenotypic traits controlled by increased Sonic hedgehog (Shh) signaling along the embryonic midline. The enhancement of primitive hematopoietic domains, which are formed bilaterally in the anterior and posterior lateral plate mesoderm, are responsible for the development of more larval erythrocytes in cavefish relative to surface fish. In this study, we determine the role of hypoxia and Shh signaling in the development and evolution of primitive hematopoiesis in cavefish. We show that hypoxia treatment during embryogenesis increases primitive hematopoiesis and erythrocyte development in surface fish. We also demonstrate that upregulation of Shh midline signaling by the Smoothened agonist SAG increases primitive hematopoiesis and erythrocyte development in surface fish, whereas Shh downregulation via treatment with the Smoothened inhibitor cyclopamine decreases these traits in cavefish. Together these results suggest that hematopoietic enhancement is regulated by hypoxia and Shh signaling. Lastly, we demonstrate that hypoxia enhances expression of Shh signaling along the midline of surface fish embryos. We conclude that hypoxia-mediated Shh plasticity may be a driving force for the adaptive evolution of primitive hematopoiesis and erythrocyte development in cavefish.