The zebrafish mutants dre, uki, and lep encode negative regulators of the hedgehog signaling pathway.

Proliferation is one of the basic processes that control embryogenesis. To identify factors involved in the regulation of proliferation, we performed a zebrafish genetic screen in which we used proliferating cell nuclear antigen (PCNA) expression as a readout. Two mutants, hu418B and hu540A, show increased PCNA expression. Morphologically both mutants resembled the dre (dreumes), uki (ukkie), and lep (leprechaun) mutant class and both are shown to be additional uki alleles. Surprisingly, although an increased size is detected of multiple structures in these mutant embryos, adults become dwarfs. We show that these mutations disrupt repressors of the Hedgehog (Hh) signaling pathway. The dre, uki, and lep loci encode Su(fu) (suppressor of fused), Hip (Hedgehog interacting protein), and Ptc2 (Patched2) proteins, respectively. This class of mutants is therefore unique compared to previously described Hh mutants from zebrafish genetic screens, which mainly show loss of Hh signaling. Furthermore, su(fu) and ptc2 mutants have not been described in vertebrate model systems before. Inhibiting Hh activity by cyclopamine rescues uki and lep mutants and confirms the overactivation of the Hh signaling pathway in these mutants. Triple uki/dre/lep mutants show neither an additive increase in PCNA expression nor enhanced embryonic phenotypes, suggesting that other negative regulators, possibly Ptc1, prevent further activation of the Hh signaling pathway. The effects of increased Hh signaling resulting from the genetic alterations in the uki, dre, and lep mutants differ from phenotypes described as a result of Hh overexpression and therefore provide additional insight into the role of Hh signaling during vertebrate development

Investigation of the role of VHL-HIF signaling in DNA repair and apoptosis in zebrafish

pVHL is a tumor suppressor. The lack of its function leads to various tumors, among which ccRCC (clear cell renal cell carcinoma) has the most serious outcome due to its resistance to chemotherapies and radiotherapies. Although HIF promotes the progression of ccRCC, the precise mechanism by which the loss of VHL leads to tumor initiation remains unclear. We exploited two zebrafish vhl mutants, vhl and vll, and Tg (phd3:: EGFP)i144 fish to identify crucial functions of Vhl in tumor initiation. Through the mutant analysis, we found that the role of pVHL in DNA repair is conserved in zebrafish Vll. Interestingly, we also discovered that Hif activation strongly suppressed genotoxic stress induced DNA repair defects and apoptosis in vll and brca2 mutants and in embryos lacking ATM activity. These results suggest the potential of HIF as a clinical modulator that can protect cells from accumulating DNA damage and apoptosis which can lead to cancers and neurodegenerative disorders

Asymmetric Hapln1a drives regionalized cardiac ECM expansion and promotes heart morphogenesis in zebrafish development

Aims Vertebrate heart development requires the complex morphogenesis of a linear tube to form the mature organ, a process essential for correct cardiac form and function, requiring coordination of embryonic laterality, cardiac growth, and regionalized cellular changes. While previous studies have demonstrated broad requirements for extracellular matrix (ECM) components in cardiac morphogenesis, we hypothesized that ECM regionalization may fine tune cardiac shape during heart development. Methods and results Using live in vivo light sheet imaging of zebrafish embryos, we describe a left-sided expansion of the ECM between the myocardium and endocardium prior to the onset of heart looping and chamber ballooning. Analysis using an ECM sensor revealed the cardiac ECM is further regionalized along the atrioventricular axis. Spatial transcriptomic analysis of gene expression in the heart tube identified candidate genes that may drive ECM expansion. This approach identified regionalized expression of hapln1a, encoding an ECM cross-linking protein. Validation of transcriptomic data by in situ hybridization confirmed regionalized hapln1a expression in the heart, with highest levels of expression in the future atrium and on the left side of the tube, overlapping with the observed ECM expansion. Analysis of CRISPR-Cas9-generated hapln1a mutants revealed a reduction in atrial size and reduced chamber ballooning. Loss-of-function analysis demonstrated that ECM expansion is dependent upon Hapln1a, together supporting a role for Hapln1a in regionalized ECM modulation and cardiac morphogenesis. Analysis of hapln1a expression in zebrafish mutants with randomized or absent embryonic left–right asymmetry revealed that laterality cues position hapln1a-expressing cells asymmetrically in the left side of the heart tube. Conclusion We identify a regionalized ECM expansion in the heart tube which promotes correct heart development, and propose a novel model whereby embryonic laterality cues orient the axis of ECM asymmetry in the heart, suggesting these two pathways interact to promote robust cardiac morphogenesis

Underlying molecular mechanisms of DIO2 susceptibility in symptomatic osteoarthritis

Objectives: To investigate how the genetic susceptibility gene DIO2 confers risk to osteoarthritis (OA) onset in humans and to explore whether counteracting the deleterious effect could contribute to novel therapeutic approaches. Methods: Epigenetically regulated expression of DIO2 was explored by assessing methylation of positional CpG-dinucleotides and the respective DIO2 expression in OA-affected and macroscopically preserved articular cartilage from end-stage OA patients. In a human in vitro chondrogenesis model, we measured the effects when thyroid signalling during culturing was either enhanced (excess T3 or lentiviral induced DIO2 overexpression) or decreased (iopanoic acid). Results: OA-related changes in methylation at a specific CpG dinucleotide upstream of DIO2 caused significant upregulation of its expression (ß=4.96; p=0.0016). This effect was enhanced and appeared driven specifically by DIO2 rs225014 risk allele carriers (ß=5.58, p=0.0006). During in vitro chondrogenesis, DIO2 overexpression resulted in a significant reduced capacity of chondrocytes to deposit extracellular matrix (ECM) components, concurrent with significant induction of ECM degrading enzymes (ADAMTS5, MMP13) and markers of mineralisation (ALPL, COL1A1). Given their concurrent and significant upregulation of expression, this process is likely mediated via HIF-2a/RUNX2 signalling. In contrast, we showed that inhibiting deiodinases during in vitro chondrogenesis contributed to prolonged cartilage homeostasis as reflected by significant increased deposition of ECM components and attenuated upregulation of matrix degrading enzymes. Conclusions: Our findings show how genetic variation at DIO2 could confer risk to OA and raised the possibility that counteracting thyroid signalling may be a novel therapeutic approach

Grading immunohistochemical markers p16INK4a and HPV E4 identifies productive and transforming lesions caused by low- and high-risk HPV within high-grade anal squamous intraepithelial lesions

Objectives: Because current guidelines recognise high-grade anal squamous intraepithelial lesions (HSILs) and low-grade SILs (LSILs), and recommend treatment of all HSILs although not all progress to cancer, this study aims to distinguish transforming and productive HSILs by grading immunohistochemical (IHC) biomarkers p16INK 4a (p16) and E4 in low-risk human papillomavirus (lrHPV) and high-risk (hr)HPV-associated SILs as a potential basis for more selective treatment. Methods: Immunostaining for p16 and HPV E4 was performed and graded in 183 biopsies from 108 HIV-positive men who have sex with men. The causative HPV genotype of the worst lesion was identified using the HPV SPF10-PCR-DEIA-LiPA25 version 1 system, with laser capture microdissection for multiple infections. The worst lesions were scored for p16 (0–4) to identify activity of the hrHPV E7 gene, and panHPV E4 (0–2) to mark HPV production and life cycle completion. Results: There were 37 normal biopsies, 60 LSILs and 86 HSILs, with 85% of LSILs caused by lrHPV and 93% of HSILs by hrHPV. No normal biopsy showed E4, but 43% of LSILs and 37% of HSILs were E4 positive. No differences in E4 positivity rates were found between lrHPV and hrHPV lesions. Most of the lesions caused by lrHPV (90%) showed very extensive patchy p16 staining; p16 grade in HSILs was variable, with frequency of productive HPV infection dropping with increasing p16 grade. Conclusions: Combined p16/E4 IHC identifies productive and nonproductive HSILs associated with hrHPV within the group of HSILs defined by the Lower Anogenital Squamous Terminology recommendations. This opens the possibility of investigating selective treatment of advanced transforming HSILs caused by hrHPV, and a ‘wait and see’ policy for productive HSILs. What's already known about this topic?. For preventing anal cancer in high-risk populations, all patients with high-grade squamous intraepithelial lesions (HSILs) are treated, even though this group of lesions is heterogeneous, the histology is variable and regression is frequent. What does this study add?. By adding human papillomavirus (HPV) E4 immunohistochemistry to p16 INK4a (p16), and grading expression of both markers, different biomarker expression patterns that reflect the heterogeneity of HSILs can be identified. Moreover, p16/E4 staining can separate high-risk HPV-associated HSILs into productive and more advanced transforming lesions, providing a potential basis for selective treatment

Convenient synthetic route to antimicrobial benzo[c]pyranquinones

A genera) synthetic strategy has been developed for the synthesis of racemic 3,4-dihydro-3-methyl-1 Hbenzo[ c]pyran-5,8-dione 25, trans-0 fl,3fl)-5,8-dihydroxy-1,3-dimethyl-4-oxo-lH-benzo[cjpyran 39, rel- {1fl,3R,4H)-3,4-dihydro-1,3-dimethyl-4-hydroxy-1H-benzo[c]pyran-5,8-dione 41 and the re/-(4S)-diastereoisomer 42

Hedgehog signaling plays a cell-autonomous role in maximizing cardiac developmental potential.

Elucidation of the complete roster of signals required for myocardial specification is crucial to the future of cardiac regenerative medicine. Prior studies have implicated the Hedgehog (Hh) signaling pathway in the regulation of multiple aspects of heart development. However, our understanding of the contribution of Hh signaling to the initial specification of myocardial progenitor cells remains incomplete. Here, we show that Hh signaling promotes cardiomyocyte formation in zebrafish. Reduced Hh signaling creates a cardiomyocyte deficit, and increased Hh signaling creates a surplus. Through fate-mapping, we find that Hh signaling is required at early stages to ensure specification of the proper number of myocardial progenitors. Genetic inducible fate mapping in mouse indicates that myocardial progenitors respond directly to Hh signals, and transplantation experiments in zebrafish demonstrate that Hh signaling acts cell autonomously to promote the contribution of cells to the myocardium. Thus, Hh signaling plays an essential early role in defining the optimal number of cardiomyocytes, making it an attractive target for manipulation of multipotent progenitor cells

[An unusual presentation of a periappendicular infiltrate]

Item does not contain fulltextA 17-year-old boy presented with an atypical manifestation of acute appendicitis. The clinical aspect, radiological investigations and peroperative aspect of the appendix were not conclusive but nevertheless a neuroendocrine tumour (carcinoid tumour) of the appendix was suspected. After ileocaecal resection and resection of pathological lymph nodes, histopathological evaluation revealed the diagnosis: a periappendicular mass without any sign of malignancy. In retrospect, ileocaecal resection was performed for a benign disease. This case illustrates that an unusual presentation of a common disease occurs more frequently than a typical presentation of a rare disease

A zebrafish model for VHL and hypoxia signaling

The von Hippel-Lindau (VHL) tumor suppressor gene encodes an adaptor protein that regulates an array of transcription-dependent and -independent cellular and physiological processes. Mutations in this gene cause VHL disease, congenital polycythemia, and several sporadic tumor types. The last 15 years of fundamental and clinical research have helped define the phenotypic spectrum of VHL-associated diseases and have introduced new cellular functions for pVHL. Here, we review the current knowledge of VHL function, and the different animal models for VHL disease, with a particular focus on the zebrafish. Zebrafish vhl mutants develop key aspects of the human disease condition, including activation of the hypoxia-inducible factor (HIF) signaling pathway, polycythemia, excessive neovascularization, macular edema, and pronephric abnormalities. The zebrafish vhl model offers a platform for the identification of genetic pathways, modifiers, and interactors involved in the development of VHL-associated neoplasms. Vhl mutants represent a unique and clinically relevant in vivo model for studying genotype-phenotype correlations and the identification of prognostic biomarkers. The amenability of zebrafish for chemical genetic screens will not only be helpful to identify novel therapeutic agents but may also reveal novel processes that require regulation by VHL

von Hippel-Lindau tumor suppressor mutants faithfully model pathological hypoxia-driven angiogenesis and vascular retinopathies in zebrafish

Biallelic inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene predisposes human patients to the development of highly vascularized neoplasms in multiple organ systems. We show that zebrafish vhl mutants display a marked increase in blood vessel formation throughout the embryo, starting at 2 days post-fertilization. The most severe neovascularization is observed in distinct areas that overlap with high vegfa mRNA expression, including the vhl mutant brain and eye. Real-time quantitative PCR revealed increased expression of the duplicated VEGFA orthologs vegfaa and vegfab, and of vegfb and its receptors flt1, kdr and kdr-like, indicating increased vascular endothelial growth factor (Vegf) signaling in vhl mutants. Similar to VHL-associated retinal neoplasms, diabetic retinopathy and age-related macular degeneration, we show, by tetramethyl rhodamine-dextran angiography, that vascular abnormalities in the vhl(-/-) retina lead to vascular leakage, severe macular edema and retinal detachment. Significantly, vessels in the brain and eye express cxcr4a, a marker gene expressed by tumor and vascular cells in VHL-associated hemangioblastomas and renal cell carcinomas. VEGF receptor (VEGFR) tyrosine kinase inhibition (through exposure to sunitinib and 676475) blocked vhl(-/-)-induced angiogenesis in all affected tissues, demonstrating that Vegfaa, Vegfab and Vegfb are key effectors of the vhl(-/-) angiogenic phenotype through Flt1, Kdr and Kdr-like signaling. Since we show that the vhl(-/-) angiogenic phenotype shares distinct characteristics with VHL-associated vascular neoplasms, zebrafish vhl mutants provide a valuable in vivo vertebrate model to elucidate underlying mechanisms contributing to the development of these lesions. Furthermore, vhl mutant zebrafish embryos carrying blood vessel-specific transgenes represent a unique and clinically relevant model for tissue-specific, hypoxia-induced pathological angiogenesis and vascular retinopathies. Importantly, they will allow for a cost-effective, non-invasive and efficient way to screen for novel pharmacological agents and combinatorial treatments