Comprehensive and Integrative Genomic Characterization of Hepatocellular Carcinoma.

Liver cancer has the second highest worldwide cancer mortality rate and has limited therapeutic options. We analyzed 363 hepatocellular carcinoma (HCC) cases by whole-exome sequencing and DNA copy number analyses, and we analyzed 196 HCC cases by DNA methylation, RNA, miRNA, and proteomic expression also. DNA sequencing and mutation analysis identified significantly mutated genes, including LZTR1, EEF1A1, SF3B1, and SMARCA4. Significant alterations by mutation or downregulation by hypermethylation in genes likely to result in HCC metabolic reprogramming (ALB, APOB, and CPS1) were observed. Integrative molecular HCC subtyping incorporating unsupervised clustering of five data platforms identified three subtypes, one of which was associated with poorer prognosis in three HCC cohorts. Integrated analyses enabled development of a p53 target gene expression signature correlating with poor survival. Potential therapeutic targets for which inhibitors exist include WNT signaling, MDM4, MET, VEGFA, MCL1, IDH1, TERT, and immune checkpoint proteins CTLA-4, PD-1, and PD-L1.

Structure, mechanism, and inhibition of Hedgehog acyltransferase.

The Sonic Hedgehog (SHH) morphogen pathway is fundamental for embryonic development and stem cell maintenance and is implicated in various cancers. A key step in signaling is transfer of a palmitate group to the SHH N terminus, catalyzed by the multi-pass transmembrane enzyme Hedgehog acyltransferase (HHAT). We present the high-resolution cryo-EM structure of HHAT bound to substrate analog palmityl-coenzyme A and a SHH-mimetic megabody, revealing a heme group bound to HHAT that is essential for HHAT function. A structure of HHAT bound to potent small-molecule inhibitor IMP-1575 revealed conformational changes in the active site that occlude substrate binding. Our multidisciplinary analysis provides a detailed view of the mechanism by which HHAT adapts the membrane environment to transfer an acyl chain across the endoplasmic reticulum membrane. This structure of a membrane-bound O-acyltransferase (MBOAT) superfamily member provides a blueprint for other protein-substrate MBOATs and a template for future drug discovery.

The developmental stage of the medulloblastoma cell-of-origin restricts Sonic hedgehog pathway usage and drug sensitivity.

Sonic hedgehog (SHH) medulloblastoma originates from the cerebellar granule neuron progenitor (CGNP) lineage, which depends on Hedgehog signaling for its perinatal expansion. Whereas SHH tumors exhibit overall deregulation of this pathway, they also show patient age-specific aberrations. To investigate whether the developmental stage of the CGNP can account for these age-specific lesions, we analyzed developing murine CGNP transcriptomes and observed highly dynamic gene expression as a function of age. Cross-species comparison with human SHH medulloblastoma showed partial maintenance of these expression patterns, and highlighted low primary cilium expression as hallmark of infant medulloblastoma and early embryonic CGNPs. This coincided with reduced responsiveness to upstream SHH pathway component Smoothened, whereas sensitivity to downstream components SUFU and GLI family proteins was retained. Together, these findings can explain the preference for SUFU mutations in infant medulloblastoma and suggest that drugs targeting the downstream SHH pathway will be most appropriate for infant patients.

Androgen action in cell fate and communication during prostate development at single-cell resolution.

Androgens/androgen receptor (AR)-mediated signaling pathways are essential for prostate development, morphogenesis and regeneration. Specifically, stromal AR signaling has been shown to be essential for prostatic initiation. However, the molecular mechanisms underlying AR-initiated mesenchymal-epithelial interactions in prostate development remain unclear. Here, using a newly generated mouse model, we have directly addressed the fate and role of genetically marked AR-expressing cells during embryonic prostate development. Androgen signaling-initiated signaling pathways were identified in mesenchymal niche populations at single-cell transcriptomic resolution. The dynamic cell-signaling networks regulated by stromal AR were additionally characterized in relation to prostatic epithelial bud formation. Pseudotime analyses further revealed the differentiation trajectory and fate of AR-expressing cells in both prostatic mesenchymal and epithelial cell populations. Specifically, the cellular properties of Zeb1-expressing progenitors were assessed. Selective deletion of AR signaling in a subpopulation of mesenchymal rather than epithelial cells dysregulated the expression of the master regulators and significantly impaired prostatic bud formation. These data provide novel, high-resolution evidence demonstrating the important role of mesenchymal androgen signaling in the cellular niche controlling prostate early development by initiating dynamic mesenchyme-epithelia cell interactions.

Stromal androgen and hedgehog signaling regulates stem cell niches in pubertal prostate development.

Stromal androgen-receptor (AR) action is essential for prostate development, morphogenesis and regeneration. However, mechanisms underlying how stromal AR maintains the cell niche in support of pubertal prostatic epithelial growth are unknown. Here, using advanced mouse genetic tools, we demonstrate that selective deletion of stromal AR expression in prepubescent Shh-responsive Gli1-expressing cells significantly impedes pubertal prostate epithelial growth and development. Single-cell transcriptomic analyses showed that AR loss in these prepubescent Gli1-expressing cells dysregulates androgen signaling-initiated stromal-epithelial paracrine interactions, leading to growth retardation of pubertal prostate epithelia and significant development defects. Specifically, AR loss elevates Shh-signaling activation in both prostatic stromal and adjacent epithelial cells, directly inhibiting prostatic epithelial growth. Single-cell trajectory analyses further identified aberrant differentiation fates of prostatic epithelial cells directly altered by stromal AR deletion. In vivo recombination of AR-deficient stromal Gli1-lineage cells with wild-type prostatic epithelial cells failed to develop normal prostatic epithelia. These data demonstrate previously unidentified mechanisms underlying how stromal AR-signaling facilitates Shh-mediated cell niches in pubertal prostatic epithelial growth and development.

ZIC1 Dictates Osteogenesis Versus Adipogenesis in Human Mesenchymal Progenitor Cells Via a Hedgehog Dependent Mechanism.

Numerous intrinsic factors regulate mesenchymal progenitor commitment to a specific cell fate, such as osteogenic or adipogenic lineages. Identification and modulation of novel intrinsic regulatory factors represent an opportunity to harness the regenerative potential of mesenchymal progenitors. In the present study, the transcription factor (TF) ZIC1 was identified to be differentially expressed among adipose compared with skeletal-derived mesenchymal progenitor cells. We observed that ZIC1 overexpression in human mesenchymal progenitors promotes osteogenesis and prevents adipogenesis. ZIC1 knockdown demonstrated the converse effects on cell differentiation. ZIC1 misexpression was associated with altered Hedgehog signaling, and the Hedgehog antagonist cyclopamine reversed the osteo/adipogenic differentiation alterations associated with ZIC1 overexpression. Finally, human mesenchymal progenitor cells with or without ZIC1 overexpression were implanted in an ossicle assay in NOD-SCID gamma mice. ZIC1 overexpression led to significantly increased ossicle formation in comparison to the control, as assessed by radiographic and histologic measures. Together, these data suggest that ZIC1 represents a TF at the center of osteo/adipogenic cell fate determinations-findings that have relevance in the fields of stem cell biology and therapeutic regenerative medicine.

IGFBP5 Promotes Neuronal Apoptosis in a 6-OHDA-Toxicant Model of Parkinson's Disease by Inhibiting the Sonic Hedgehog Signaling Pathway.

INTRODUCTION: Parkinson's disease (PD) is the most common neurodegenerative disease worldwide. Studies have shown that insulin-like growth factor-binding protein 5 (IGFBP5) may contribute to methamphetamine-induced neurotoxicity and neuronal apoptosis in PC-12 cells and rat striatum. Here, we studied the expression and role of IGFBP5 in the 6-OHDA-toxicant model of PD. METHODS: PC-12 and SH-SY5Y cells were exposed to 50 µm 6-OHDA for 24 h. qRT-PCR, western blotting, CCK-8 assay, EdU staining, annexin V staining, and immunofluorescence were performed to study the effects of IGFBP5-specific siRNAs. The effects of IGFBP5 on a rat 6-OHDA model of PD were confirmed by performing behavioral tests, tyrosine hydroxylase (TH) immunofluorescence staining, and western blotting. RESULTS: In the GSE7621 dataset, IGFBP5 was highly expressed in the substantia nigra tissues of PD patients compared to healthy controls. In PC-12 and SH-SY5Y cells, IGFBP5 was upregulated following 6-OHDA exposure in a dose-dependent manner. Silencing of IGFBP5 promoted PC-12 and SH-SY5Y proliferation and inhibited apoptosis under 6-OHDA stimulation. Silencing of IGFBP5 relieved 6-OHDA-induced TH-positive neuron loss. Hedgehog signaling pathway was predicted as a downstream signaling pathway of IGFBP5. Negative regulation between IGFBP5 and sonic hedgehog (SHH) signaling pathway was confirmed in vitro. The effects of IGFBP5 silencing on SH-SY5Y cells were partially reversed using cyclopamine, a direct inhibitor of the SHH signaling pathway. In addition, silencing of IGFBP5 attenuated motor deficits and neuronal damage in 6-OHDA-induced PD rats. CONCLUSION: Elevated IGFBP5 expression may be involved in 6-OHDA-induced neurotoxicity through regulation of the SHH signaling pathway.

Sonic Hedgehog Signaling Pathway: A Role in Pain Processing.

Pain, as one of the most prevalent clinical symptoms, is a complex physiological and psychological activity. Long-term severe pain can become unbearable to the body. However, existing treatments do not provide satisfactory results. Therefore, new mechanisms and therapeutic targets need to be urgently explored for pain management. The Sonic hedgehog (Shh) signaling pathway is crucial in embryonic development, cell differentiation and proliferation, and nervous system regulation. Here, we review the recent studies on the Shh signaling pathway and its action in multiple pain-related diseases. The Shh signaling pathway is dysregulated under various pain conditions, such as pancreatic cancer pain, bone cancer pain, chronic post-thoracotomy pain, pain caused by degenerative lumbar disc disease, and toothache. Further studies on the Shh signaling pathway may provide new therapeutic options for pain patients.

Sirt1 regulates microglial activation and inflammation following oxygen-glucose deprivation/reoxygenation injury by targeting the Shh/Gli-1 signaling pathway.

BACKGROUND: Cerebral ischemic injury leads to over-activation of microglia, which release pro-inflammatory factors that deteriorate neurological function during the acute phase of stroke. Thus, inhibiting microglial over-activation is crucial for reducing ischemic injury. Sirtuin 1 (Sirt1) has been shown to play a critical role in stroke, neurodegenerative diseases and aging. However, the effect of Sirt1 on the regulation of microglial activation following cerebral ischemic injury, as well as the underlying mechanism, remain unknown. Therefore, the purpose of the present study is to mainly investigate the effect of Sirt1 on oxygen-glucose deprivation/reoxygenation (OGD/R)-treated N9 microglia following treatment with the Sirt1 agonists resveratrol and SRT1720 and the Sirt1 antagonist sirtinol. METHODS: Cell viability, Apoptosis, activation and inflammatory responses of microglia, expressions and activity of Shh signaling pathway proteins were detected by Cell Counting Kit 8, Flow Cytometry, immunocytochemistry, ELISA, and Western blotting, respectively. RESULTS: The results demonstrated that treatment with resveratrol or SRT1720 could inhibit the activation of microglia and inflammation during OGD/R. Moreover, these treatments also led to the translocation of the GLI family zinc finger-1 (Gli-1) protein from the cytoplasm to the nucleus and upregulated the expression of Sonic hedgehog (Shh), Patched homolog-1 (Ptc-1), smoothened frizzled class receptor and Gli-1. By contrast, the inhibition of Sirt1 using sirtinol had the opposite effect. CONCLUSION: These findings suggested that Sirt1 may regulate microglial activation and inflammation by targeting the Shh/Gli-1 signaling pathway following OGD/R injury. Schematic representation of Sirt1 regulating the microglial activation and inflammation following oxygen-glucose deprivation/reoxygenation injury via mediation of Shh/Gli-1 signaling pathway.

Metformin exerts anti-tumor effects via Sonic hedgehog signaling pathway by targeting AMPK in HepG2 cells.

Metformin, a traditional first-line pharmacological treatment for type 2 diabetes, has recently been shown to have anti-cancer effects on hepatocellular carcinoma (HCC). However, the molecular mechanism underlying the anti-tumor activity of metformin remains unclear. The Sonic hedgehog (Shh) signaling pathway is closely associated with the initiation and progression of HCC. Therefore, the aim of the current study was to investigate the effects of metformin on the biological behavior of HCC and the underlying functional mechanism of metformin in the Shh pathway. HCC was induced in HepG2 cells using recombinant human Shh (rhShh). The effects of metformin on proliferation and metastasis were evaluated using in vitro proliferation, wound healing, and invasion assays. The mRNA and protein expression levels of proteins related to the Shh pathway were measured using western blotting, quantitative PCR, and immunofluorescence staining. Metformin inhibited rhShh-induced proliferation and metastasis. Furthermore, metformin decreased the mRNA and protein expression of Shh pathway components, including Shh, Ptch, Smo, and Gli-1. Silencing of AMPK in the presence of metformin revealed that metformin exerted its inhibitory effects via AMPK. Our findings demonstrate that metformin suppresses the migration and invasion of HepG2 cells via AMPK-mediated inhibition of the Shh pathway.

Emerging role of non-coding RNAs in the regulation of Sonic Hedgehog signaling pathway.

Sonic Hedgehog (Shh) signaling cascade is one of the complex signaling pathways that control the accurately organized developmental processes in multicellular organisms. This pathway has fundamental roles in the tumor formation and induction of resistance to conventional therapies. Numerous non-coding RNAs (ncRNAs) have been found to interact with Shh pathway to induce several pathogenic processes, including malignant and non-malignant disorders. Many of the Shh-interacting ncRNAs are oncogenes whose expressions have been increased in diverse malignancies. A number of Shh-targeting miRNAs such as miR-26a, miR-1471, miR-129-5p, miR-361-3p, miR-26b-5p and miR-361-3p have been found to be down-regulated in tumor tissues. In addition to malignant conditions, Shh-interacting ncRNAs can affect tissue regeneration and development of neurodegenerative disorders. XIST, LOC101930370, lncRNA-Hh, circBCBM1, SNHG6, LINC-PINT, TUG1 and LINC01426 are among long non-coding RNAs/circular RNAs that interact with Shh pathway. Moreover, miR-424, miR-26a, miR-1471, miR-125a, miR-210, miR-130a-5p, miR-199b, miR-155, let-7, miR-30c, miR-326, miR-26b-5p, miR-9, miR-132, miR-146a and miR-425-5p are among Shh-interacting miRNAs. The current review summarizes the interactions between ncRNAs and Shh in these contexts.

Understanding Abnormal SMO-SHH Signaling in Autism Spectrum Disorder: Potential Drug Target and Therapeutic Goals.

Autism is a multifactorial neurodevelopmental condition; it demonstrates some main characteristics, such as impaired social relationships and increased repetitive behavior. The initiation of autism spectrum disorder is mostly triggered during brain development by the deregulation of signaling pathways. Sonic hedgehog (SHH) signaling is one such mechanism that influences neurogenesis and neural processes during the development of the central nervous system. SMO-SHH signaling is also an important part of a broad variety of neurological processes, including neuronal cell differentiation, proliferation, and survival. Dysregulation of SMO-SHH signaling leads to many physiological changes that lead to neurological disorders such as ASD and contribute to cognitive decline. The aberrant downregulation of SMO-SHH signals contributes to the proteolytic cleavage of GLI (glioma-associated homolog) into GLI3 (repressor), which increases oxidative stress, neuronal excitotoxicity, neuroinflammation, and apoptosis by suppressing target gene expression. We outlined in this review that SMO-SHH deregulation plays a crucial role in the pathogenesis of autism and addresses the current status of SMO-SHH pathway modulators. Additionally, a greater understanding of the SHH signaling pathway is an effort to improve successful treatment for autism and other neurological disorders.

The First 50 Years of Postnatal Neurogenesis in the Cerebellum: a Long Journey Across Phenomena, Mechanisms, and Human Disease.

The discovery by Altman and coworkers of adult-born microneurons in the olfactory bulb and dentate gyrus has triggered a long stream of studies and many attempts to harness adult neurogenesis, promote regeneration after injury, and contrast cognitive decline in the elderly. Likewise, the discovery of postnatal neurogenesis in the cerebellum has provided the framework for many subsequent molecular studies, including investigations of developmental processes and the assessment of GC progenitor (GCP) clonal expansion in the context of human disease. Here, I will briefly discuss some of the discoveries made in the field of cerebellar development over the years building upon the findings of Altman and his colleagues, touching upon signaling pathways that regulate granule cell neurogenesis and their involvement in developmental and neoplastic disorders of the cerebellum.

Expression of Shh, Gli1, and Cyr61 in Gastric Cancer Predicts Overall Survival of Patients: A Retrospective Study.

OBJECTIVE: This study aimed to evaluate the expression levels of Shh, Gli1, and Cyr61 proteins in gastric cancer tissues and analyze the relationship between these three proteins and the clinicopathological factors and prognosis of patients. METHODS: This was a retrospective study. Four hundred gastric cancer tissue specimens from patients who underwent radical gastrectomy in Zhangye People's Hospital affiliated to Hexi University between February 2013 and February 2021 underwent immunohistochemical analysis. RESULTS: The positive expression rates of Shh, Gli1, and Cyr61 in gastric cancer tissues were 55.5%, 56.5%, and 64.5%, respectively. The expressions of Shh, Gli1, and Cyr61 in gastric cancer tissues were significantly correlated with tumor size, depth of invasion, and degree of differentiation (P < .05). The expression of Shh protein was positively correlated with the expression of Gli1 protein (P < .01), and the expression of Gli1 protein was positively correlated with the expression of Cyr61 protein (P < .01). Univariate and multivariate analyses showed that the expression of Shh, Gli1, and Cyr61 could predict the prognosis of patients (P < .05). Receiver operating characteristic curve analysis combined with TNM staging could better predict the three-year overall survival of patients (P < .05). CONCLUSION: Shh, Gli1, and Cyr61 proteins are significantly expressed in gastric cancer tissues and are risk factors for the prognosis of patients with gastric cancer.

Dl-3-n-butylphthalide promotes neurite outgrowth of primary cortical neurons by Sonic Hedgehog signaling via upregulating Gap43.

Neurite outgrowth is the basis for wiring during the development of the nervous system. Dl-3-n-butylphthalide (NBP) has been recognized as a promising treatment to improve behavioral, neurological and cognitive outcomes in ischemic stroke. However, little is known about the effect and mechanism of NBP on the neurite outgrowth. In this study, we used different methods to investigate the potential effects of NBP on the neurite extension and plasticity of immature and mature primary cortical neurons and explored the underlying mechanisms. Our results demonstrated that in immature and mature cortical neurons, NBP promoted the neurite length and intersections, increased neuritic arborization, elevated numbers of neurite branch and terminal points and improved neurite complexity and plasticity of neuronal development processes. Besides, our data revealed that NBP promoted neurite extension and branching partly by activating Shh signaling pathway via increasing Gap43 expression both in immature and mature primary cortical neurons. The present study provided new insights into the contribution of NBP in neuronal plasticity and unveiled a novel pathway to induce Gap43 expression in primary cortical neurons.

Regulator of cullins-1 (ROC1) negatively regulates the Gli2 regulator SUFU to activate the hedgehog pathway in bladder cancer.

BACKGROUND: The regulator of cullins-1 (ROC1) is an essential subunit in the cullin-RING ligase (CRL) protein complex and has been shown to be critical in bladder cancer cell survival and progression. This study aimed to explore the molecular mechanism of ROC1 action in the malignant progression of bladder cancer. METHODS: This study utilized ex vivo, in vitro, and in vivo nude mouse experiments to assess the underlying mechanisms of ROC1 in bladder cancer cells. The expression of the components of the sonic hedgehog (SHH) pathway was determined by western blot analysis. ROC1 expression in human tumors was evaluated by immunohistochemistry. RESULTS: ROC1 overexpression promoted the growth of bladder cancer cells, whereas knockdown of ROC1 expression had the opposite effect in bladder cancer cells. Mechanistically, ROC1 was able to target suppressor of fused homolog (SUFU) for ubiquitin-dependent degradation, allowing Gli2 release from the SUFU complex to activate the SHH pathway. Furthermore, knockdown of SUFU expression partially rescued the ROC1 knockdown-suppressed SHH activity as well as cancer cell growth inhibition. In ex vivo experiments, tissue microarray analysis of human bladder cancer specimens revealed a positive association of ROC1 expression with the SHH pathway activity. CONCLUSION: This study demonstrated that dysregulation of the ROC1-SUFU-GLI2 axis plays an important role in bladder cancer progression and that targeting ROC1 expression is warranted in further investigations as a novel strategy for the future control of bladder cancer.

Quercetin suppresses pancreatic ductal adenocarcinoma progression via inhibition of SHH and TGF-ß/Smad signaling pathways.

Pancreatic ductal adenocarcinoma (PDA) is an aggressive type of malignant tumor with a poor prognosis and high mortality. Aberrant activation of hedgehog signaling plays a crucial role in the maintenance and progression of PDA. Here, we report that the dietary bioflavonoid quercetin has therapeutic potential for PDA by targeting sonic hedgehog (SHH) signaling. The effects of quercetin on the proliferation, apoptosis, migration, and invasion of pancreatic cancer cells (PCCs) and tumor growth and metastasis in PDA xenograft mouse models were evaluated. Additionally, SHH signaling activity was determined. Quercetin significantly inhibited PCC proliferation by downregulating c-Myc expression. In addition, quercetin suppressed epithelial-mesenchymal transition (EMT) by reducing TGF-ß1 level, which resulted in inhibition of PCC migration and invasion. Moreover, quercetin induced PCC apoptosis through mitochondrial and death receptor pathways. In nude mouse models, PDA growth and metastasis were reduced by quercetin treatment. Mechanically, quercetin exerts its therapeutic effects on PDA by decreasing SHH activity. Interestingly, quercetin-induced SHH inactivation is mainly dependent on Gli2, but not Gli1. Enhance SHH activity by recombinant Shh protein abolished the quercetin-mediated inhibition of PCC proliferation, migration, and invasion. Furthermore, Shh activated TGF-ß1/Smad2/3 signaling and promoted EMT by inducing the expression of Zeb2 and Snail1 that eventually resulted in a partial reversal of quercetin-mediated inhibition of PCC migration and invasion. We conclude that quercetin inhibited the growth, migration, and invasion and induced apoptosis of PCCs by antagonizing SHH and TGF-ß/Smad signaling pathways. Thus, quercetin may be a potential candidate for PDA treatment.

Specific temperament in patients with nevoid basal cell carcinoma syndrome.

BACKGROUND: Nevoid basal cell carcinoma syndrome (NBCCS) is a neurocutaneous disease, characterized by tumorigenesis and developmental anomalies due to aberrant sonic hedgehog (Shh) signaling. Patients with NBCCS typically appear calm and carefree, suggesting that a specific personality in these patients may be associated with an enhanced hedgehog pathway. Our study aimed to determine the personality type in these patients. METHODS: We enrolled 14 mentally normal patients with genetically confirmed NBCCS (seven males and seven females; mean age = 25.2 years) and 20 controls (10 males and 10 females; mean age = 27.9 years). The patients were assessed with the Japanese version of the Temperament and Character Inventory, based on the seven-dimensional model of temperament and character, and their clinical symptoms were evaluated. The amygdala volumes of six patients with NBCCS were measured using magnetic resonance imaging with image-processing software. RESULTS: Patients with NBCCS scored significantly lower on harm avoidance (0.89) than controls (1.00; P = 0.0084). Moreover, patients with NBCCS and developmental malformations such as rib anomalies, who may have experienced Shh signaling enhancement from the prenatal period, scored significantly lower on harm avoidance (0.80 [P = 0.0031]). The left amygdala volume was also significantly reduced in patients with NBCCS (P = 0.0426). CONCLUSIONS: Patients with NBCCS who experienced increased Shh signaling from the prenatal period showed significantly lower harm avoidance related to serotonin. The left amygdala volume was significantly reduced in these patients. Our results indicate that Shh signaling may influence the human personality.

Shh-Yap signaling controls hepatic ductular reactions in CCl4 -induced liver injury.

Carbon tetrachloride (CCl4 ) exposure can induce hepatic ductular reactions. To date, however, the related mechanism remains largely unknown. Sonic hedgehog (Shh) and Yes-associated protein (Yap) signaling are correlated with liver injury and regeneration. Herein, we investigated the role of Shh and Yap signaling in the fate of ductular reaction cells in CCl4 -treated livers and the possible mechanisms. Wild-type and Shh-EGFP-Cre male mice were exposed to CCl4 (2 mL/kg), and then treated with or without the Shh signaling inhibitor Gant61. The level of liver injury, proliferation of ductular reaction cells, and expression levels of mRNA and protein related to the Shh and Yap signaling components were assessed. Results showed that CCl4 treatment induced liver injury and promoted activation and proliferation of ductular reaction cells. In addition, CCl4 induced the expression of Shh ligands in hepatocytes, accompanied by activation of Shh and Yap1 signaling in the liver. Furthermore, administration of Gant61 ameliorated liver regeneration, inhibited hepatic ductular reactions, and decreased Shh and Yap1 signaling activity. Thus, Shh-Yap1 signaling appears to play an integral role in the proliferation of ductular reaction cells in CCl4 -induced liver injury. This study should improve our understanding of the mechanism of CCl4 -induced liver injury and ductular reactions and provide support for future investigations on liver disease therapy.

Mechanical Brain Injury Increases Cells' Production of Cystathionine ß-Synthase and Glutamine Synthetase, but Reduces Pax2 Expression in the Telencephalon of Juvenile Chum Salmon, Oncorhynchus keta.

The considerable post-traumatic brain recovery in fishes makes them a useful model for studying the mechanisms that provide reparative neurogenesis, which is poorly represented in mammals. After a mechanical injury to the telencephalon in adult fish, lost neurons are actively replaced due to the proliferative activity of neuroepithelial cells and radial glia in the neurogenic periventricular zone. However, it is not enough clear which signaling mechanisms are involved in the activation of adult neural stem cells (aNSC) after the injury (reactive proliferation) and in the production of new neurons (regenerative neurogenesis) from progenitor cells (NPC). In juvenile Pacific salmon, the predominant type of NSCs in the telencephalon are neuroepithelial cells corresponding to embryonic NSCs. Expression of glutamine synthetase (GS), a NSC molecular marker, was detected in the neuroepithelial cells of the pallium and subpallium of juvenile chum salmon, Oncorhynchus keta. At 3 days after a traumatic brain injury (TBI) in juvenile chum salmon, the GS expression was detected in the radial glia corresponding to aNSC in the pallium and subpallium. The maximum density of distribution of GS+ radial glia was found in the dorsal pallial region. Hydrogen sulfide (H2S) is a proneurogenic factor that reduces oxidative stress and excitotoxicity effects, along with the increased GS production in the brain cells of juvenile chum salmon. In the fish brain, H2S producing by cystathionine ß-synthase in neurogenic zones may be involved in maintaining the microenvironment that provides optimal conditions for the functioning of neurogenic niches during constitutive neurogenesis. After injury, H2S can determine cell survivability, providing a neuroprotective effect in the area of injury and reducing the process of glutamate excitotoxicity, acting as a signaling molecule involved in changing the neurogenic environment, which leads to the reactivation of neurogenic niches and cell regeneration programs. The results of studies on the control of the expression of regulatory Sonic Hedgehog genes (Shh) and the transcription factors Paired Box2 (Pax2) regulated by them are still insufficient. A comparative analysis of Pax2 expression in the telencephalon of intact chum salmon showed the presence of constitutive patterns of Pax2 expression in neurogenic areas and non-neurogenic parenchymal zones of the pallium and subpallium. After mechanical injury, the patterns of Pax2 expression changed, and the amount of Pax2+ decreased (p < 0.05) in lateral (Dl), medial (Dm) zones of the pallium, and the lateral zone (Vl) of the subpallium compared to the control. We believe that the decrease in the expression of Pax2 may be caused by the inhibitory effect of the Pax6 transcription factor, whose expression in the juvenile salmon brain increases upon injury.