CMG2/ANTXR2 regulates extracellular collagen VI which accumulates in hyaline fibromatosis syndrome

Endotrophin, a Key Marker and Driver for Fibroinflammatory Disease

Our overview covers several key areas related to recent results obtained for collagen type VI and endotrophin (ETP). (1) An introduction to the history of ETP, including how it was identified, how it is released, and its function and potential receptors. (2) An introduction to the collagen family, with a focus on what differentiates collagen type VI from an evolutionary standpoint. (3) An overview of collagen type VI, the 6 individual chains (COL6A1, A2, A3, A4, A5, and A6), their differences and similarities, as well as their expression profiles and function. (4) A detailed analysis of COL6A3, including the cleaved product endotrophin, and what separates it from the other 5 collagen 6 molecules, including its suggested function based on insights gained from knockout and gain of function mouse models. (5) The pathology of ETP. What leads to its presence and release and what are the consequences thereof? (6) Functional implications of circulating ETP. Here we review the data with the functional roles of ETP in mind. (7) We propose that ETP is a mediator for fibrotic (or fibroinflammatory) disorders. Based on what we know about ETP, we have to consider it as a target for the treatment of fibrotic (or fibroinflammatory) disorders. What segment(s) of the patient population would most dramatically respond to an ETP-targeted intervention? How can we find the population that would profit most from an intervention? We aim to present a broad overview over the ETP field at large, providing an assessment of where the future research efforts need to be placed to tap into the vast potential of ETP, both as a marker and as a target in different diseases.

ANTXR1 deficiency promotes fibroblast senescence: implications for GAPO syndrome as a progeroid disorder

ANTXR1 is one of two cell surface receptors mediating the uptake of the anthrax toxin into cells. Despite substantial research on its role in anthrax poisoning and a proposed function as a collagen receptor, ANTXR1's physiological functions remain largely undefined. Pathogenic variants in ANTXR1 lead to the rare GAPO syndrome, named for its four primary features: Growth retardation, Alopecia, Pseudoanodontia, and Optic atrophy. The disease is also associated with a complex range of other phenotypes impacting the cardiovascular, skeletal, pulmonary and nervous systems. Aberrant accumulation of extracellular matrix components and fibrosis are considered to be crucial components in the pathogenesis of GAPO syndrome, contributing to the shortened life expectancy of affected individuals. Nonetheless, the specific mechanisms connecting ANTXR1 deficiency to the clinical manifestations of GAPO syndrome are largely unexplored. In this study, we present evidence that ANTXR1 deficiency initiates a senescent phenotype in human fibroblasts, correlating with defects in nuclear architecture and actin dynamics. We provide novel insights into ANTXR1's physiological functions and propose GAPO syndrome to be reconsidered as a progeroid disorder highlighting an unexpected role for an integrin-like extracellular matrix receptor in human aging.

Hyaline Fibromatosis Syndrome Diagnosed by Whole Genome Sequencing

Hyaline fibromatosis syndrome is an extremely rare autosomal recessive condition caused by biallelic pathogenic variants in the ANTXR2 gene that leads to abnormal growth of hyalinized fibrous tissue. Severity ranges from life-threatening intractable diarrhea, recurrent infection, and acute pain to milder disease resulting in skin lesions and less severe contractures. Here, we report the case of a 3-month-old female who presented with joint contractures and severe pain followed by failure to thrive. Diagnosis via ultra-rapid whole genome sequencing allowed our team to provide appropriate care and anticipatory guidance for this patient and family.

Endothelial anthrax toxin receptor 2 plays a protective role in liver fibrosis

Hepatocellular carcinoma is one of the leading cancers worldwide and is a potential consequence of fibrosis. Therefore, the identification of key cellular and molecular mechanisms involved in liver fibrosis is an important goal for the development of new strategies to control liver-related diseases. Here, single-cell RNA sequencing data (GSE136103 and GES181483) of clinical liver non-parenchymal cells were analyzed to identify cellular and molecular mechanisms of liver fibrosis. The proportion of endothelial subpopulations in cirrhotic livers was significantly higher than that in healthy livers. Gene ontology and gene set enrichment analysis of differentially expressed genes in the endothelial subgroups revealed that extracellular matrix (ECM)-related pathways were significantly enriched. Since anthrax toxin receptor 2 (ANTXR2) interacts with the ECM, the expression of ANTXR2 in the liver endothelium was analyzed. ANTXR2 expression in the liver endothelium of wild-type (WT) mice significantly decreased after a 4-time sequential injection of carbon tetrachloride (CCl4) to induce liver fibrosis. Next, conditional knockout mice selectively lacking Antxr2 in endothelial cells were generated. After endothelial-specific Antxr2 knockout mice were subjected to the CCl4 model, the degree of liver fibrosis in the knockout group was significantly more severe than that in the control group. In addition, ANTXR2 in human umbilical vein endothelial cells promoted matrix metalloproteinase 2 (MMP2) activation to degrade the ECM in vitro. Finally, endothelial-specific overexpression of Antxr2 alleviated the development of liver fibrosis following adeno-associated virus treatment. Collectively, these results suggested that endothelial ANTXR2 plays a protective role in liver fibrosis. This function of ANTXR2 may be achieved by promoting MMP2 activation to degrade the ECM.

Epithelial cell invasion by salmonella typhimurium induces modulation of genes controlled by aryl hydrocarbon receptor signaling and involved in extracellular matrix biogenesis

Salmonella is the only bacterium able to enter a host cell by the two known mechanisms: trigger and zipper. The trigger mechanism relies on the injection of bacterial effectors into the host cell through the Salmonella type III secretion system 1. In the zipper mechanism, mediated by the invasins Rck and PagN, the bacterium takes advantage of a cellular receptor for invasion. This study describes the transcriptomic reprogramming of the IEC-6 intestinal epithelial cell line to Salmonella Typhimurium strains that invaded cells by a trigger, a zipper, or both mechanisms. Using S. Typhimurium strains invalidated for one or other entry mechanism, we have shown that IEC-6 cells could support both entries. Comparison of the gene expression profiles of exposed cells showed that irrespective of the mechanism used for entry, the transcriptomic reprogramming of the cell was nearly the same. On the other hand, when gene expression was compared between cells unexposed or exposed to the bacterium, the transcriptomic reprogramming of exposed cells was significantly different. It is particularly interesting to note the modulation of expression of numerous target genes of the aryl hydrocarbon receptor showing that this transcription factor was activated by S. Typhimurium infection. Numerous genes associated with the extracellular matrix were also modified. This was confirmed at the protein level by western-blotting showing a dramatic modification in some extracellular matrix proteins. Analysis of a selected set of modulated genes showed that the expression of the majority of these genes was modulated during the intracellular life of S. Typhimurium.

Multisystemic Manifestations of Hyaline Fibromatosis Syndrome: Implications for Diagnosis and Management

Hyaline fibromatosis syndrome (HFS) is a rare autosomal recessive disorder characterized by the deposition of hyaline material in the skin, soft tissues, and bones. In this report, we discuss a case of a six-month-old male with HFS who presented with faltering growth, chronic diarrhea, multiple joint contractures, joint stiffness, hyperpigmented skin over bony prominences, gingival hypertrophy, patent foramen ovale, and symmetric periventricular hyperintensities on brain MRI. The diagnosis of HFS was confirmed by skin biopsy and genetic testing, which identified a homozygous mutation in the anthrax toxin receptor 2 (ANTXR2) gene. The patient was managed symptomatically with nutritional support, physiotherapy, analgesics, and regular dental care. He also received intralesional corticosteroid therapy, which significantly decreased the size of the skin nodules. His hyperpigmented skin and gingival hypertrophy remained stable, and the patent foramen ovale was managed conservatively. This case report highlights the importance of early diagnosis and management of HFS and the benefits of involving a multidisciplinary team to improve the quality of life of affected individuals.

Extracellular vesicles stimulate smooth muscle cell migration by presenting collagen VI

The extracellular matrix (ECM) supports blood vessel architecture and functionality and undergoes active remodelling during vascular repair and atherogenesis. Vascular smooth muscle cells (VSMCs) are essential for vessel repair and, via their secretome, are able to invade from the vessel media into the intima to mediate ECM remodelling. Accumulation of fibronectin (FN) is a hallmark of early vascular repair and atherosclerosis and here we show that FN stimulates VSMCs to secrete small extracellular vesicles (sEVs) by activating the β1 integrin/FAK/Src pathway as well as Arp2/3-dependent branching of the actin cytoskeleton. Spatially, sEV were secreted via filopodia-like cellular protrusions at the leading edge of migrating cells. We found that sEVs are trapped by the ECM in vitro and colocalise with FN in symptomatic atherosclerotic plaques in vivo. Functionally, ECM-trapped sEVs induced the formation of focal adhesions (FA) with enhanced pulling forces at the cellular periphery. Proteomic and GO pathway analysis revealed that VSMC-derived sEVs display a cell adhesion signature and are specifically enriched with collagen VI. In vitro assays identified collagen VI as playing the key role in cell adhesion and invasion. Taken together our data suggests that the accumulation of FN is a key early event in vessel repair acting to promote secretion of collage VI enriched sEVs by VSMCs. These sEVs stimulate migration and invasion by triggering peripheral focal adhesion formation and actomyosin contraction to exert sufficient traction forces to enable VSMC movement within the complex vascular ECM network.

New Clinical and Immunofluoresence Data of Collagen VI-Related Myopathy: A Single Center Cohort of 69 Patients

Pathogenetic mechanism recognition and proof-of-concept clinical trials were performed in our patients affected by collagen VI-related myopathies. This study, which included 69 patients, aimed to identify innovative clinical data to better design future trials. Among the patients, 33 had Bethlem myopathy (BM), 24 had Ullrich congenital muscular dystrophy (UCMD), 7 had an intermediate phenotype (INTM), and five had myosclerosis myopathy (MM). We obtained data on muscle strength, the degree of contracture, immunofluorescence, and genetics. In our BM group, only one third had a knee extension strength greater than 50% of the predicted value, while only one in ten showed similar retention of elbow flexion. These findings should be considered when recruiting BM patients for future trials. All the MM patients had axial and limb contractures that limited both the flexion and extension ranges of motion, and a limitation in mouth opening. The immunofluorescence analysis of collagen VI in 55 biopsies from 37 patients confirmed the correlation between collagen VI defects and the severity of the clinical phenotype. However, biopsies from the same patient or from patients with the same mutation taken at different times showed a progressive increase in protein expression with age. The new finding of the time-dependent modulation of collagen VI expression should be considered in genetic correction trials.

Collagen VI sustains cell stemness and chemotherapy resistance in glioblastoma

Microenvironmental factors are known fundamental regulators of the phenotype and aggressiveness of glioblastoma (GBM), the most lethal brain tumor, characterized by fast progression and marked resistance to treatments. In this context, the extracellular matrix (ECM) is known to heavily influence the behavior of cancer cells from several origins, contributing to stem cell niches, influencing tumor invasiveness and response to chemotherapy, mediating survival signaling cascades, and modulating inflammatory cell recruitment. Here, we show that collagen VI (COL6), an ECM protein widely expressed in both normal and pathological tissues, has a distinctive distribution within the GBM mass, strongly correlated with the most aggressive and phenotypically immature cells. Our data demonstrate that COL6 sustains the stem-like properties of GBM cells and supports the maintenance of an aggressive transcriptional program promoting cancer cell proliferation and survival. In particular, we identified a specific subset of COL6-transcriptionally co-regulated genes, required for the response of cells to replicative stress and DNA damage, supporting the concept that COL6 is an essential stimulus for the activation of GBM cell response and resistance to chemotherapy, through the ATM/ATR axis. Altogether, these findings indicate that COL6 plays a pivotal role in GBM tumor biology, exerting a pleiotropic action across different GBM hallmarks, including phenotypic identity and gene transcription, as well as response to treatments, thus providing valuable information for the understanding of the complex microenvironmental cues underlying GBM malignancy.

Collagen VI in the Musculoskeletal System

Collagen VI exerts several functions in the tissues in which it is expressed, including mechanical roles, cytoprotective functions with the inhibition of apoptosis and oxidative damage, and the promotion of tumor growth and progression by the regulation of cell differentiation and autophagic mechanisms. Mutations in the genes encoding collagen VI main chains, COL6A1, COL6A2 and COL6A3, are responsible for a spectrum of congenital muscular disorders, namely Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM) and myosclerosis myopathy (MM), which show a variable combination of muscle wasting and weakness, joint contractures, distal laxity, and respiratory compromise. No effective therapeutic strategy is available so far for these diseases; moreover, the effects of collagen VI mutations on other tissues is poorly investigated. The aim of this review is to outline the role of collagen VI in the musculoskeletal system and to give an update about the tissue-specific functions revealed by studies on animal models and from patients' derived samples in order to fill the knowledge gap between scientists and the clinicians who daily manage patients affected by collagen VI-related myopathies.

Croix B. Cancer cell survival depends on collagen uptake into tumor-associated stroma

Collagen I, the most abundant protein in humans, is ubiquitous in solid tumors where it provides a rich source of exploitable metabolic fuel for cancer cells. While tumor cells were unable to exploit collagen directly, here we show they can usurp metabolic byproducts of collagen-consuming tumor-associated stroma. Using genetically engineered mouse models, we discovered that solid tumor growth depends upon collagen binding and uptake mediated by the TEM8/ANTXR1 cell surface protein in tumor-associated stroma. Tumor-associated stromal cells processed collagen into glutamine, which was then released and internalized by cancer cells. Under chronic nutrient starvation, a condition driven by the high metabolic demand of tumors, cancer cells exploited glutamine to survive, an effect that could be reversed by blocking collagen uptake with TEM8 neutralizing antibodies. These studies reveal that cancer cells exploit collagen-consuming stromal cells for survival, exposing an important vulnerability across solid tumors with implications for developing improved anticancer therapy.

Host Cell Transcriptional Tuning with CRISPR/dCas9 to Mitigate the Effects of Toxin Exposure

Anthrax infection is caused byBacillus anthracis, a bacterium that once established within the host releases lethal toxin (LeTx). Anthrax LeTx is internalized by the capillary morphogenesis protein 2/anthrax toxin receptor 2 (CMG2/ANTXR2) cell surface receptor on mammalian cells. Once inside the cell, LeTx cleaves mitogen-activated protein kinases (MAPKs), ultimately leading to cell death. Previous reports have shown that decreased expression of ANTXR2 reduces cell susceptibility to LeTx. By ablating the ANTXR2 gene in cells in vitro, we observed complete resistance to LeTx-induced cell death. Here, we directed CRISPR/dCas9-based tools to the ANTXR2 promoter to modulate ANTXR2 expression without altering the underlying gene sequence in human cell lines that express the receptor at high levels. We hypothesized that downregulating the expression of the ANTXR2 gene at the genomic level would mitigate the impact of toxin exposure. In one epigenetic editing approach, we employed the fusion of DNMT3A DNA methyltransferase and dCas9 (dCas9-DNMT3A) to methylate CpGs within the CpG island of the ANTXR2 promoter and found this repressed ANTXR2 gene expression resulting in significant resistance to LeTx-induced cell death. Furthermore, by multiplexing gRNAs to direct dCas9-DNMT3A to multiple sites in the ANTXR2 promoter, we applied a broader distribution of CpG methylation along the gene promoter resulting in enhanced repression and resistance to LeTx. In parallel, we directed the dCas9-KRAB-MeCP2 transcriptional repressor to the ANTXR2 promoter to quickly and robustly repress ANTXR2 expression. With this approach, in as little as two weeks, we created resistance to LeTx at a similar level to ANTXR2 gene-ablated cells. Overall, we present a transcriptional tuning approach to inhibit the effects of LeTx and provide a framework to repress toxin-binding cell surface receptors.

Lack of evidence for a role of anthrax toxin receptors as surface receptors for collagen VI and for its cleaved-off C5 domain/endotrophin

The microfibril-forming collagen VI is proteolytically cleaved and it was proposed that the released C-terminal Kunitz domain (C5) of the α3 chain is an adipokine important for tumor progression and fibrosis. Designated “endotrophin,” C5 is a potent biomarker for fibroinflammatory diseases. However, the biochemical mechanisms behind endotrophin activity were not investigated. Earlier, anthrax toxin receptor 1 was found to bind C5, but this potential interaction was not further studied. Given the proposed physiological role of endotrophin, we aimed to determine how the signal is transmitted. Surprisingly, we could not detect any interaction between endotrophin and anthrax toxin receptor 1 or its close relative, anthrax toxin receptor 2. Moreover, we detect no binding of fully assembled collagen VI to either receptor. We also studied the collagen VI receptor NG2 (CSPG4) and confirmed that NG2 binds assembled collagen VI, but not cleaved C5/endotrophin. A cellular receptor for C5/endotrophin, therefore, still remains elusive.

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ANTXR1 does not support collagen VI or C5/endotrophin binding to the cell surface

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ANTXR2 does not support collagen VI or C5/endotrophin binding to the cell surface

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NG2/CSPG4 supports collagen VI, but not C5/endotrophin binding to the cell surface

The Capillary Morphogenesis Gene 2 Triggers the Intracellular Hallmarks of Collagen VI-Related Muscular Dystrophy

Collagen VI-related disorders (COL6-RD) represent a severe form of congenital disease for which there is no treatment. Dominant-negative pathogenic variants in the genes encoding α chains of collagen VI are the main cause of COL6-RD. Here we report that patient-derived fibroblasts carrying a common single nucleotide variant mutation are unable to build the extracellular collagen VI network. This correlates with the intracellular accumulation of endosomes and lysosomes triggered by the increased phosphorylation of the collagen VI receptor CMG2. Notably, using a CRISPR-Cas9 gene-editing tool to silence the dominant-negative mutation in patients’ cells, we rescued the normal extracellular collagen VI network, CMG2 phosphorylation levels, and the accumulation of endosomes and lysosomes. Our findings reveal an unanticipated role of CMG2 in regulating endosomal and lysosomal homeostasis and suggest that mutated collagen VI dysregulates the intracellular environment in fibroblasts in collagen VI-related muscular dystrophy.

Juvenile Hyaline Fibromatosis: Report of a Case with a Novel ANTXR2 Gene Mutation

BACKGROUND Juvenile hyaline fibromatosis is a rare autosomal recessive disorder with unknown prevalence characterized by abnormal development of hyalinized fibrous tissue usually in the skin, mucosa, bone, and often the internal organs. Here, we report the case of a 7-year-old girl from a family with ANTXR2 mutation confirming JHF. CASE REPORT The girl presented with multiple painless soft-tissue swellings affecting the ears, forehead, and scalp. Excisional biopsies of the masses reported positive immunohistochemical staining for collagen type VI in the extracellular matrix area, which indicated collagen VI accumulation. Genetic analysis was performed using whole-exome sequencing. The variants were further validated using Sanger sequencing in trio-based approach. We identified a novel mutation, c.1273_1293delinsTCTTGTGGGTTTGGCT in exon 15 of ANTXR2 gene, leading to a frameshift of the amino acid from codon 425 to all the rest of the amino acid chain (p.Pro425Serfs). The change of an encoded protein interrupted lysosome-mediated degradation of collagen VI. This finding was compatible with her parents whose genetic tests were both positive for the same heterogenous deletion/insertion mutation. The patient was treated with surgical excision of the tumor masses, which had to be repeated several times due to recurrences. CONCLUSIONS This novel mutation in exon 15 of the ANTXR2 gene may help improve understanding of genotype-phenotype correlations for this syndrome and provide the basis for diagnostic testing. A multidisciplinary team approach including genetic molecular testing is required for an accurate diagnosis and management of JHF for conducting genetic counseling for affected families as a part of holistic management.

Update of pediatric soft tissue tumors with review of conventional MRI appearance-part 1: tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors

There are numerous soft tissue tumors and tumor-like conditions in the pediatric population. Magnetic resonance imaging is the most useful modality for imaging these lesions. Although certain soft tissue lesions exhibit magnetic resonance features characteristic of a specific diagnosis, most lesions are indeterminate, and a biopsy is necessary for diagnosis. We provide a detailed update of soft tissue tumors and tumor-like conditions that occur in the pediatric population, emphasizing each lesion's conventional magnetic resonance imaging appearance, using the recently released 5th edition of the World Health Organization Classification of Soft Tissue and Bone Tumors as a guide. In part one of this review, pediatric tumor-like lesions, adipocytic tumors, fibroblastic and myofibroblastic tumors, and perivascular tumors are discussed. In part two, vascular lesions, fibrohistiocytic tumors, muscle tumors, peripheral nerve sheath tumors, tumors of uncertain differentiation, and undifferentiated small round cell sarcomas are reviewed. Per the convention of the WHO, these lesions involve the connective, subcutaneous, and other non-parenchymatous-organ soft tissues, as well as the peripheral and autonomic nervous system.

Capillary morphogenesis gene 2 (CMG2) mediates growth factor-induced angiogenesis by regulating endothelial cell chemotaxis

Anthrax protective antigen (PA) is a potent inhibitor of pathological angiogenesis with an unknown mechanism. In anthrax intoxication, PA interacts with capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8). Here, we show that CMG2 mediates the antiangiogenic effects of PA and is required for growth-factor-induced chemotaxis. Using specific inhibitors of CMG2 and TEM8 interaction with natural ligand, as well as mice with the CMG2 or TEM8 transmembrane and intracellular domains disrupted, we demonstrate that inhibiting CMG2, but not TEM8 reduces growth-factor-induced angiogenesis in the cornea. Furthermore, the antiangiogenic effect of PA was abolished when the CMG2, but not the TEM8, gene was disrupted. Binding experiments demonstrated a broad ligand specificity for CMG2 among extracellular matrix (ECM) proteins. Ex vivo experiments demonstrated that CMG2 (but not TEM8) is required for PA activity in human dermal microvascular endothelial cell (HMVEC-d) network formation assays. Remarkably, blocking CMG2-ligand binding with PA or CRISPR knockout abolishes endothelial cell chemotaxis but not chemokinesis in microfluidic migration assays. These effects are phenocopied by Rho inhibition. Because CMG2 mediates the chemotactic response of endothelial cells to peptide growth factors in an ECM-dependent fashion, CMG2 is well-placed to integrate growth factor and ECM signals. Thus, CMG2 targeting is a novel way to inhibit angiogenesis.

Anthrax toxins regulate pain signaling and can deliver molecular cargoes into ANTXR2+ DRG sensory neurons

Bacterial products can act on neurons to alter signaling and function. In the present study, we found that dorsal root ganglion (DRG) sensory neurons are enriched for ANTXR2, the high-affinity receptor for anthrax toxins. Anthrax toxins are composed of protective antigen (PA), which binds to ANTXR2, and the protein cargoes edema factor (EF) and lethal factor (LF). Intrathecal administration of edema toxin (ET (PA + EF)) targeted DRG neurons and induced analgesia in mice. ET inhibited mechanical and thermal sensation, and pain caused by formalin, carrageenan or nerve injury. Analgesia depended on ANTXR2 expressed by Na_v1.8⁺ or Advillin⁺ neurons. ET modulated protein kinase A signaling in mouse sensory and human induced pluripotent stem cell-derived sensory neurons, and attenuated spinal cord neurotransmission. We further engineered anthrax toxins to introduce exogenous protein cargoes, including botulinum toxin, into DRG neurons to silence pain. Our study highlights interactions between a bacterial toxin and nociceptors, which may lead to the development of new pain therapeutics.

Juvenile hyaline fibromatosis: A clinicopathological study of five cases

Juvenile hyaline fibromatosis (JHF) is an extremely rare autosomal recessive disease that typically presents in infancy or early childhood. Largely due to the rarity, JHF is still not widely recognized by clinicians and pathologists in China. It is not uncommonly to misdiagnose the disease as other types of disorders. In this study, we present our experience with five cases of JHF to enhance the recognition of this rare but distinctive entity. There were 4 males and 1 female, with age at presentation ranging from 5 to 44 years. All patients presented with multiple subcutaneous nodular lesions of varying size in various parts of the body since birth or early childhood. Three patients also had joint involvement. Pathologically, the lesions were poorly circumscribed, located mainly in the dermis and subcutis. All five cases were characterized by abundant homogeneous hyaline-like matrix that differs sharply from the adjacent connective tissue, which stained strongly with periodic acid-Schiff (PAS) and was diastase resistant. Embedded within the eosinophilic glassy matrix were cords or small clusters of plump spindled to epithelioid cells, frequently with clear cytoplasm. Familiarity with the characteristic features of JHF is not only important in avoiding misdiagnosis but also essential for clinical management and prognostic evaluation.

Infantile systemic hyalinosis: Variable grades of severity

BACKGROUND

Infantile systemic hyalinosis (ISH) is an autosomal recessively inherited disorder. The classical natural history of the disease is characterised by hypotonia, multiple contractures, skin lesions, osteopenia, joint pain, bone fractures, persistent diarrhoea and growth deficiency.

MATERIALS AND METHODS

Two children manifested the severe type of ISH underwent genotypic confirmation. In order to identify which other family members have inherited the disease. We included siblings and cousins in this study. The baseline tool to study other family subjects was based on the phenotypic characterisations of each child.

RESULTS

. Two children with the severe type of ISH showed craniosynostosis (brachycephaly and scaphocephaly) associated with multiple contractures, progressive joint osteolysis ending up with multiple joint dislocations. The full exome sequencing was carried out, revealing a previously reported heterozygous nonsense mutation с.1294С>Т and a novel heterozygous non-synonymous substitution c. 58T>A in ANTRX2 gene. Three children (sibling and cousins) manifested variable clinical manifestations relevant to ISH. Specifically, asymptoamtic skin and skeletal abnormalities of hypoplastic clavicles and 'shepherd's crook' deformity and coxa vara.

CONCLUSION

It is mandatory to perform extensive family pedigree search to detect asymptomatic clinical features in siblings and cousins in families with first degree related marriages. Interestingly, in the mild and the moderate types of ISH, we observed undescribed combination of asymptomatic skin and skeletal abnormalities. This is a comparative study between the severe and the mild/moderate types in a group of children from consanguineous families. Our current study extends the phenotypic characterisations of ISH.

Collagen-VI supplementation by cell transplantation improves muscle regeneration in Ullrich congenital muscular dystrophy model mice

Background

Mesenchymal stromal cells (MSCs) function as supportive cells on skeletal muscle homeostasis through several secretory factors including type 6 collagen (COL6). Several mutations of COL6A1, 2, and 3 genes cause Ullrich congenital muscular dystrophy (UCMD). Skeletal muscle regeneration deficiency has been reported as a characteristic phenotype in muscle biopsy samples of human UCMD patients and UCMD model mice. However, little is known about the COL6-dependent mechanism for the occurrence and progression of the deficiency. The purpose of this study was to clarify the pathological mechanism of UCMD by supplementing COL6 through cell transplantation.

Methods

To test whether COL6 supplementation has a therapeutic effect for UCMD, in vivo and in vitro experiments were conducted using four types of MSCs: (1) healthy donors derived-primary MSCs (pMSCs), (2) MSCs derived from healthy donor induced pluripotent stem cell (iMSCs), (3) COL6-knockout iMSCs (COL6KO-iMSCs), and (4) UCMD patient-derived iMSCs (UCMD-iMSCs).

Results

All four MSC types could engraft for at least 12 weeks when transplanted into the tibialis anterior muscles of immunodeficient UCMD model (Col6a1KO) mice. COL6 protein was restored by the MSC transplantation if the MSCs were not COL6-deficient (types 1 and 2). Moreover, muscle regeneration and maturation in Col6a1KO mice were promoted with the transplantation of the COL6-producing MSCs only in the region supplemented with COL6. Skeletal muscle satellite cells derived from UCMD model mice (Col6a1KO-MuSCs) co-cultured with type 1 or 2 MSCs showed improved proliferation, differentiation, and maturation, whereas those co-cultured with type 3 or 4 MSCs did not.

Conclusions

These findings indicate that COL6 supplementation improves muscle regeneration and maturation in UCMD model mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02514-3.

Genetic deletion of CMG2 exacerbates systemic-to-pulmonary shunt-induced pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) secondary to congenital heart disease (CHD-PAH) with systemic-to-pulmonary shunt (SPS) is characterized by proliferative vascular remodeling. Capillary morphogenesis gene-2 (CMG2) plays a key role in cell proliferation and apoptosis. This study aimed to determine the role of CMG2 in the pathogenesis of SPS-induced PAH. CMG2 levels were significantly downregulated in pulmonary arterioles from patients with Eisenmenger syndrome and rats with SPS-induced PAH. CMG2 was highly expressed in several cells including human pulmonary arterial smooth muscle cells (HPASMCs). CMG2^-/- rats exhibited more severe PAH and pulmonary vascular remodeling than wild-type rats when exposed to SPS for 8 weeks. Overexpression of CMG2 significantly inhibited proliferation and promoted apoptosis of HPASMCs, while knockdown of CMG2 promoted cell proliferation and inhibited cell apoptosis. Next-generation sequencing and subsequent validation results suggested that PI3K-AKT was the most prominent signaling pathway regulated by differentially expressed genes (DEGs) in CMG2^-/- rat lungs. Our work identified a novel role for CMG2 in SPS-induced PAH based on the findings that CMG2 deficiency exacerbates SPS-induced vascular remodeling in the development of PAH, indicating that CMG2 might act as a potential target for the treatment of CHD-PAH.

Collagen VI as a driver and disease biomarker in human fibrosis

Fibrosis of visceral organs such as the lungs, heart, kidneys and liver remains a major cause of morbidity and mortality and is also associated with many other disorders, including cancer and metabolic disease. In this review, we focus upon the microfibrillar collagen VI, which is present in the extracellular matrix (ECM) of most tissues. However, expression is elevated in numerous fibrotic conditions, such as idiopathic pulmonary disease (IPF), and chronic liver and kidney diseases. Collagen VI is composed of three subunits α1, α2 and α3, which can be replaced with alternate chains of α4, α5 or α6. The C-terminal globular domain (C5) of collagen VI α3 can be proteolytically cleaved to form a biologically active fragment termed endotrophin, which has been shown to actively drive fibrosis, inflammation and insulin resistance. Tissue biopsies have long been considered the gold standard for diagnosis and monitoring of progression of fibrotic disease. The identification of neoantigens from enzymatically processed collagen chains have revolutionised the biomarker field, allowing rapid diagnosis and evaluation of prognosis of numerous fibrotic conditions, as well as providing valuable clinical trial endpoint determinants. Collagen VI chain fragments such as endotrophin (PRO-C6), C6M and C6Mα3 are emerging as important biomarkers for fibrotic conditions.

Hyaline fibromatosis syndrome: A case report

Hyaline fibromatosis syndrome (HFS) is a rare monogenic disease inherited in an autosomal recessive pattern and characterized by hyaline deposits on the skin, mucosa, and multiple organs; osteoporosis; and joint contractures. This progressive condition is caused by mutations in the gene encoding the anthrax toxin receptor 2 protein (ANTXR2). HFS is a disabling disease, and patients suffer from progressive pain and disfiguring symptoms. There are few published case reports detailing oral findings in patients with this condition. The present case report describes a 4-year-old female patient who showed severe manifestations of HFS, emphasizing the oral manifestations, the histopathologic aspects of HFS, the molecular pathogenesis, and the interdisciplinary management of patients affected by this condition.

Houwen R, Barshack I, Somech R, Nieuwenhuis EE, Sagi I, Raas-Rothschild A, Middendorp S, Shouval DS. Enhanced Collagen Deposition in the Duodenum of Patients with Hyaline Fibromatosis Syndrome and Protein Losing Enteropathy

Hyaline fibromatosis syndrome (HFS), resulting from ANTXR2 mutations, is an ultra-rare disease that causes intestinal lymphangiectasia and protein-losing enteropathy (PLE). The mechanisms leading to the gastrointestinal phenotype in these patients are not well defined. We present two patients with congenital diarrhea, severe PLE and unique clinical features resulting from deleterious ANTXR2 mutations. Intestinal organoids were generated from one of the patients, along with CRISPR-Cas9 ANTXR2 knockout, and compared with organoids from two healthy controls. The ANTXR2-deficient organoids displayed normal growth and polarity, compared to controls. Using an anthrax-toxin assay we showed that the c.155C>T mutation causes loss-of-function of ANTXR2 protein. An intrinsic defect of monolayer formation in patient-derived or ANTXR2KO organoids was not apparent, suggesting normal epithelial function. However, electron microscopy and second harmonic generation imaging showed abnormal collagen deposition in duodenal samples of these patients. Specifically, collagen VI, which is known to bind ANTXR2, was highly expressed in the duodenum of these patients. In conclusion, despite resistance to anthrax-toxin, epithelial cell function, and specifically monolayer formation, is intact in patients with HFS. Nevertheless, loss of ANTXR2-mediated signaling leads to collagen VI accumulation in the duodenum and abnormal extracellular matrix composition, which likely plays a role in development of PLE.

Anthrax Edema and Lethal Toxins Differentially Target Human Lung and Blood Phagocytes

Bacillus anthracis, the causative agent of inhalation anthrax, is a serious concern as a bioterrorism weapon. The vegetative form produces two exotoxins: Lethal toxin (LT) and edema toxin (ET). We recently characterized and compared six human airway and alveolar-resident phagocyte (AARP) subsets at the transcriptional and functional levels. In this study, we examined the effects of LT and ET on these subsets and human leukocytes. AARPs and leukocytes do not express high levels of the toxin receptors, tumor endothelium marker-8 (TEM8) and capillary morphogenesis protein-2 (CMG2). Less than 20% expressed surface TEM8, while less than 15% expressed CMG2. All cell types bound or internalized protective antigen, the common component of the two toxins, in a dose-dependent manner. Most protective antigen was likely internalized via macropinocytosis. Cells were not sensitive to LT-induced apoptosis or necrosis at concentrations up to 1000 ng/mL. However, toxin exposure inhibited B. anthracis spore internalization. This inhibition was driven primarily by ET in AARPs and LT in leukocytes. These results support a model of inhalation anthrax in which spores germinate and produce toxins. ET inhibits pathogen phagocytosis by AARPs, allowing alveolar escape. In late-stage disease, LT inhibits phagocytosis by leukocytes, allowing bacterial replication in the bloodstream.

Protective effect of anthrax toxin receptor 2 polymorphism rs4333130 against the risk of ankylosing spondylitis

BACKGROUND

The present study was performed to statistically explore the effect of anthrax toxin receptor 2 (ANTXR2) polymorphism rs4333130 on individual susceptibility to ankylosing spondylitis (AS) using the method of meta-analysis.

METHODS

All of the eligible reports were retrieved from well-known electronic databases. The strength of the association between ANTXR2 polymorphism rs4333130 and the susceptibility to AS was evaluated using pooled odds ratios (ORs) with 95% confidence intervals (95% CIs). In addition, subgroup analysis was also performed on the basis of ethnicity to further explore specific correlation between our studied polymorphism and the disease risk. Inter-study heterogeneity was detected with Q test, and P < .05 was considered statistically significant. Sensitivity analysis was implemented through removing each of eligible studies and then recalculating overall effects to test the reliability of final estimates. Publication bias among included studies was inspected with both Begg funnel plot and Egger regression test.

RESULTS

A total of 6 eligible papers were finally incorporated into the present meta-analysis. In total analysis, ANTXR2 polymorphism rs4333130 was significantly related to decreased risk of AS under CC versus TT, CC + TC versus TT, CC versus TT + TC, C versus T and TC versus TT contrasts (OR = 0.35, 95% CI = 0.20-0.64; OR = 0.81, 95% CI = 0.69-0.95; OR = 0.38, 95% CI = 0.21-0.68; OR = 0.89, 95% CI = 0.84-0.95; OR = 0.84, 95% CI = 0.72-0.99). Moreover, a similar effect was also observed in Asian and Caucasian subgroups under corresponding genetic models after stratification analysis based on ethnicity.

CONCLUSION

ANTXR2 polymorphism rs4333130 may function as a protective factor against AS incidence.

Clinical aspects of Hyaline Fibromatosis Syndrome and identification of a novel mutation

BACKGROUND

Hyaline fibromatosis syndrome is an autosomal recessive disease caused by mutations in ANTXR2 which leads to loss of function of the transmembrane protein anthrax toxin receptor 2. It is distinguished by characteristic skin lesions, gingival hyperplasia, joint and bone disease, and systemic involvement.

METHODS

Based on the case of an 11-year-old female patient with typical features of hyaline fibromatosis syndrome and the underlying pathogenic compound heterozygote variants in ANTXR2 we discuss the genetic and clinical aspects of hyaline fibromatosis syndrome.

RESULTS

The novel mutation in ANTXR2 (c.1223T>C, p.Leu408Pro variant) seems to allow for a protracted course of the disease.

CONCLUSION

Our findings add to the phenotypic, genetic, and biochemical spectrum of hyaline fibromatosis syndrome.

Ligand Binding to the Collagen VI Receptor Triggers a Talin-to-RhoA Switch that Regulates Receptor Endocytosis

Capillary morphogenesis gene 2 (CMG2/ANTXR2) is a cell surface receptor for both collagen VI and anthrax toxin. Biallelic loss-of-function mutations in CMG2 lead to a severe condition, hyaline fibromatosis syndrome (HFS). We have here dissected a network of dynamic interactions between CMG2 and various actin interactors and regulators, describing a different behavior from other extracellular matrix receptors. CMG2 binds talin, and thereby the actin cytoskeleton, only in its ligand-free state. Extracellular ligand binding leads to src-dependent talin release and recruitment of the actin cytoskeleton regulator RhoA and its effectors. These sequential interactions of CMG2 are necessary for the control of oriented cell division during fish development. Finally, we demonstrate that effective switching between talin and RhoA binding is required for the intracellular degradation of collagen VI in human fibroblasts, which explains why HFS mutations in the cytoskeleton-binding domain lead to dysregulation of extracellular matrix homeostasis.

Mammalian membrane trafficking as seen through the lens of bacterial toxins

A fundamental question of eukaryotic cell biology is how membrane organelles are organised and interact with each other. Cell biologists address these questions by characterising the structural features of membrane compartments and the mechanisms that coordinate their exchange. To do so, they must rely on variety of cargo molecules and treatments that enable targeted perturbation, localisation, and labelling of specific compartments. In this context, bacterial toxins emerged in cell biology as paradigm shifting molecules that enabled scientists to not only study them from the side of bacterial infection but also from the side of the mammalian host. Their selectivity, potency, and versatility made them exquisite tools for uncovering much of our current understanding of membrane trafficking mechanisms. Here, we will follow the steps that lead toxins until their intracellular targets, highlighting how specific events helped us comprehend membrane trafficking and establish the fundamentals of various cellular organelles and processes. Bacterial toxins will continue to guide us in answering crucial questions in cellular biology while also acting as probes for new technologies and applications.

A Canstatin-Derived Peptide Provides Insight into the Role of Capillary Morphogenesis Gene 2 in Angiogenic Regulation and Matrix Uptake

Capillary Morphogenesis Gene 2 protein (CMG2) is a transmembrane, integrin-like receptor and the primary receptor for the anthrax toxin. CMG2 also plays a role in angiogenic processes. However, the molecular mechanism that mediates the observed CMG2-related angiogenic effects is not fully elucidated. Previous studies have reported that CMG2 binds type IV collagen (Col-IV), a vital component of the vascular basement membrane, as well as other ECM proteins. Here, we further characterize the interaction between CMG2 and individual peptides from Col-IV and explore the effects of this interaction on angiogenesis. Using a peptide array, we observed that CMG2 preferentially binds peptide fragments of the NC1 (noncollagenous domain 1) domains of Col-IV. These domains are also known as the fragments arresten (from the α1 chain) and canstatin (from the α2 chain) and have documented antiangiogenic properties. A second peptide array was probed to map a putative peptide-binding epitope onto the Col-IV structure. A top hit from the initial array, a canstatin-derived peptide, binds to the CMG2 ligand-binding von Willebrand factor A (vWA) domain with a submicromolar affinity (peptide S16, K_d = 400 ± 200 nM). This peptide competes with anthrax protective antigen (PA) for CMG2 binding and does not bind CMG2 in the presence of EDTA. Together these data suggest that, like PA, S16 interacts with CMG2 at the metal-ion dependent adhesion site (MIDAS) of its vWA domain. CMG2 specifically mediates endocytic uptake of S16; both CMG2-/- endothelial cells and WT cells treated with PA show markedly reduced S16 uptake. Furthermore, S16 dramatically reduces directional endothelial cell migration with no impact on cell proliferation. These data demonstrate that this canstatin-derived peptide acts via CMG2 to elicit a marked effect on a critical process required for angiogenesis.

Anthrax toxin receptor 1/tumor endothelial marker 8 promotes gastric cancer progression through activation of the PI3K/AKT/mTOR signaling pathway

Anthrax toxin receptor 1 (ANTXR1), a type I transmembrane protein, is one of the receptors that facilitates the entrance of anthrax toxin into cells. Previous studies have confirmed the pivotal role of ANTXR1 in progression and tumorigenesis of diverse cancer types. However, the biological function of ANTXR1 in gastric cancer (GC) is still unknown. The present study aimed to investigate the role of ANTXR1 in GC and illuminate the potential molecular mechanisms. Bioinformatics analysis found that ANTXR1 expression was significantly upregulated in GC tissue and its overexpression was associated with poor prognosis of GC patients. Moreover, we confirmed the upregulation of ANTXR1 in GC cell lines and GC tissue by quantitative PCR, western blot analysis, and immunohistochemical analysis. Additionally, high protein expression level of ANTXR1 was positively associated with several clinicopathological parameters in GC patients. In our study, a series of in vitro and in vivo assays were undertaken through strategies of loss/gain‐of‐function and rescue assays. Consequently, our results indicated that ANTXR1 induced proliferation, cell cycle progression, invasion and migration, and tumorigenicity and induced suppressed apoptosis in GC. Mechanistic investigation indicated that ANTXR1 exerted its promoting effects on GC through activation of the PI3K/AKT/mTOR signaling pathway. In conclusion, our findings suggested that ANTXR1 plays a crucial role in the development and progression of GC and could serve as a novel prognostic biomarker and potential therapeutic target for GC.

Spatio-temporal expression and distribution of collagen VI during zebrafish development

Collagen VI (ColVI) is an extracellular matrix (ECM) protein involved in a range of physiological and pathological conditions. Zebrafish (Danio rerio) is a powerful model organism for studying vertebrate development and for in vivo analysis of tissue patterning. Here, we performed a thorough characterization of ColVI gene and protein expression in zebrafish during development and adult life. Bioinformatics analyses confirmed that zebrafish genome contains single genes encoding for α1(VI), α2(VI) and α3(VI) ColVI chains and duplicated genes encoding for α4(VI) chains. At 1 day post-fertilization (dpf) ColVI transcripts are expressed in myotomes, pectoral fin buds and developing epidermis, while from 2 dpf abundant transcript levels are present in myosepta, pectoral fins, axial vasculature, gut and craniofacial cartilage elements. Using newly generated polyclonal antibodies against zebrafish α1(VI) protein, we found that ColVI deposition in adult fish delineates distinct domains in the ECM of several organs, including cartilage, eye, skin, spleen and skeletal muscle. Altogether, these data provide the first detailed characterization of ColVI expression and ECM deposition in zebrafish, thus paving the way for further functional studies in this species.

Transcriptional profiling of long-intergenic noncoding RNAs in lung squamous cell carcinoma and its value in diagnosis and prognosis

Background

Long intergenic noncoding RNAs (lincRNAs) are a series of novel transcribed regions expressed in cancers that may represent candidate biomarkers for lung squamous cell carcinoma (LSqCC) treatment. In this study, we evaluated the lincRNA profile in LSqCC patients and screened valuable lincRNAs for diagnosis and prognosis.

Methods

Transcriptome profiling of 549 samples derived from 501 LSqCC patients were identified in TCGA database. 48 patients had paired primary tumor (PT) and solid normal (SN) tissue samples, while 453 patients had only PT samples. 1,771 lincRNA candidates were evaluated. Paired test (Wilcoxon two‐sample paired signed rank tests) was performed in paired PT and SN samples. Logistic regression analysis were performed in independent 453 PT samples and 48 SN samples to screen the significant lincRNAs candidates for malignances. Independent 501 PT samples were further used to screen the significant lincRNAs candidates for prognosis.

Results

Among 1,771 lincRNAs, 10 lincRNAs were significant highly‐expressed risk candidates in PT samples, and 10 protective lincRNAs candidates were significant lowly‐expressed in PT samples. Among 10 highly‐expressed risk lincRNAs, a small panel of LINC00487, LINC01927, and C10orf143 (LINC00959) could effectively predict malignancies in paired samples (AUC = 0.7274, 95%CI = (0.6264, 0.8285)). When combined with protective lincRNA candidates LINC02315, LINC00491, and LINC01697, the predictive efficiency was greatly improved in both paired samples (AUC = 0.8030, 95%CI = (0.7250, 0.8810)) and independent samples (AUC = 0.7481, 95%CI= (0.6642, 0.8320)). Additionally, three highly‐expressed risk lincRNAs, LINC01031, LINC01088, and LINC01931, were significantly associated with poor prognosis in PT samples, suggesting potential targets for anti‐LSqCC treatment.

Conclusion

Therefore, lincRNAs could be promising biomarkers for predicting malignancies and potential anti‐LSqCC targets for drug development.

Genetic, clinical and biochemical characterization of a large cohort of patients with hyaline fibromatosis syndrome

BACKGROUND

Hyaline fibromatosis syndrome (HFS) is a rare clinical condition in which bi-allelic variants in ANTXR2 are associated with extracellular hyaline deposits. It manifests as multiple skin nodules, patchy hyperpigmentation, joint contractures and severe pain with movement. HFS shows some clinical overlap to Farber disease (FD), a recessive lysosomal storage disorder.

RESULTS

We here present the largest cohort of independent, genetically confirmed HFS cases reported to date: in 19 unrelated index patients, we identified ten distinct homozygous ANTXR2 mutations, three of which are novel frame-shift variants. The associated clinical data are consistent with the previous hypothesis of non-truncating variants in the terminal exons 13-17 to confer rather mild phenotypes. The novel observation of gender-dependent disease manifestation in our cohort received support from a meta-analysis of all previously published cases. Untargeted blood-based metabolomics revealed patient samples to be biochemically distinct from control samples. Numerous potential HFS biomarker metabolites could thus be identified. We also found metabolomics profiles of HFS patients to highly overlap with those from FD patients.

CONCLUSIONS

Our study extends the mutational spectrum for HFS, suggests gender-dependency of manifestation, and provides pilot metabolomics data for biomarker identification and a better pathomechanistic understanding of the disorder.

Converging physiological roles of the anthrax toxin receptors

The anthrax toxin receptors-capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8)-were identified almost 20 years ago, although few studies have moved beyond their roles as receptors for the anthrax toxins to address their physiological functions. In the last few years, insight into their endogenous roles has come from two rare diseases: hyaline fibromatosis syndrome, caused by mutations in CMG2, and growth retardation, alopecia, pseudo-anodontia, and optic atrophy (GAPO) syndrome, caused by loss-of-function mutations in TEM8. Although CMG2 and TEM8 are highly homologous at the protein level, the difference in disease symptoms points to variations in the physiological roles of the two anthrax receptors. Here, we focus on the similarities between these receptors in their ability to regulate extracellular matrix homeostasis, angiogenesis, cell migration, and skin elasticity. In this way, we shed light on how mutations in these two related proteins cause such seemingly different diseases and we highlight the existing knowledge gaps that could form the focus of future studies.

Increased Soluble CMG2 Serum Protein Concentration is Associated with the Progression of Prostate Carcinoma

Prostate carcinoma (PCa) is one of the leading causes of cancer-related death in males, but biomarkers for the prognosis are rare. Capillary morphogenesis gene 2 (CMG2) is a modulator of extracellular matrix remodeling during angiogenesis. Four isoforms of CMG2 have been described so far, one secreted in the serum as soluble CMG2 (sCMG2). The aim of this study was to evaluate the sCMG2 serum concentrations in 179 PCa patients and 163 age-matched control subjects by ELISA and correlate it to clinical and demographic parameters. We observed that sCMG2 concentration is increased in the serum of PCa patients with metastases, while no significant differences in the concentrations were detected between the control subjects and patients with localized PCa. Furthermore, elevated sCMG2 concentrations were significantly associated with the highest T stage. Increased sCMG2 serum concentrations tended to be associated with a worsened overall and disease-specific survival of the PCa patients. In conclusion, sCMG2 may be an interesting additive biomarker for the prediction of the progression of PCa and the patients' outcome.

The Anthrax Toxin Receptor 1 (ANTXR1) Is Enriched in Pancreatic Cancer Stem Cells Derived from Primary Tumor Cultures

Pancreatic ductal adenocarcinoma (PDAC) is currently the fourth leading cause of cancer-related mortality. Cancer stem cells (CSCs) have been shown to be the drivers of pancreatic tumor growth, metastasis, and chemoresistance, but our understanding of these cells is still limited by our inability to efficiently identify and isolate them. While a number of markers capable of identifying pancreatic CSCs (PaCSCs) have been discovered since 2007, there is no doubt that more markers are still needed. The anthrax toxin receptor 1 (ANTXR1) was identified as a functional biomarker of triple-negative breast CSCs, and PDAC patients stratified based on ANTXR1 expression levels showed increased mortality and enrichment of pathways known to be necessary for CSC biology, including TGF-β, NOTCH, Wnt/β-catenin, and IL-6/JAK/STAT3 signaling and epithelial to mesenchymal transition, suggesting that ANTXR1 may represent a putative PaCSC marker. In this study, we show that ANTXR1⁺ cells are not only detectable across a panel of 7 PDAC patient-derived xenograft primary cultures but ANTXR1 expression significantly increased in CSC-enriched 3D sphere cultures. Importantly, ANTXR1⁺ cells also coexpressed other known PaCSC markers such as CD44, CD133, and autofluorescence, and ANTXR1⁺ cells displayed enhanced CSC functional and molecular properties, including increased self-renewal and expression of pluripotency-associated genes, compared to ANTXR1⁻ cells. Thus, this study validates ANTXR1 as a new PaCSC marker and we propose its use in identifying CSCs in this tumor type and its exploitation in the development of CSC-targeted therapies for PDAC.

Bacillus anthracis Protective Antigen Shows High Specificity for a UV Induced Mouse Model of Cutaneous Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) accounts for the majority of non-melanoma skin cancer related deaths, particularly in immunosuppressed persons. Identification of biomarkers that could be used to identify or treat SCC would be of significant benefit. The anthrax toxin receptors, Tumor Endothelial Marker 8 (TEM8) and Capillary Morphogenesis Gene 2 (CMG2), are endothelial receptors involved in extracellular matrix homeostasis and angiogenesis that are selectively upregulated on numerous tumors. One method of targeting these receptors is Protective Antigen (PA), a protein produced by B. anthracis that mediates binding and translocation of anthrax toxins into cells. PA targeted toxins have been demonstrated to selectively inhibit tumor growth and angiogenesis, but tumor selectivity of PA is currently unknown. In this work fluorescently labeled PA was shown to maintain receptor dependent binding and internalization in vitro. Utilizing a human papillomavirus transgenic mouse model that develops cutaneous SCC in response to ultraviolet irradiation we identified tumor uptake of PA in vivo. The intravenously administered PA resulted in tumor specific localization, with exclusive tumor detection 24 h post injection. Ex vivo analysis identified significantly higher fluorescence in the tumor compared to adjacent healthy tissue and major clearance organs, demonstrating low non-specific uptake and rapid clearance. While both TEM8 and CMG2 were observed to be overexpressed in SCC tumor sections compared to control skin, the intravenously administered PA was primarily co-localized with TEM8. These results suggest that PA could be systemically administered for rapid identification of cutaneous SCC, with potential for further therapeutic development.

Hyaline fibromatosis syndrome: Clinical update and phenotype-genotype correlations

Hyaline fibromatosis syndrome (HFS) is the unifying term for infantile systemic hyalinosis and juvenile hyaline fibromatosis. HFS is a rare autosomal recessive disorder of the connective tissue caused by mutations in the gene for anthrax toxin receptor-2 (ANTXR2). It is characterized by abnormal growth of hyalinized fibrous tissue with cutaneous, mucosal, osteoarticular, and systemic involvement. We reviewed the 84 published cases and their molecular findings, aiming to gain insight into the clinical features, prognostic factors, and phenotype-genotype correlations. Extreme pain at minimal handling in a newborn is the presentation pattern most frequently seen in grade 4 patients (life-limiting disease). Gingival hypertrophy and subcutaneous nodules are some of the disease hallmarks. Though painful joint stiffness and contractures are almost universal, weakness and hypotonia may also be present. Causes of death are intractable diarrhea, recurrent infections, and organ failure. Median age of death of grade 4 cases is 15.0 months (p25-p75: 9.5-24.0). This review provides evidence to reinforce the previous hypothesis that missense mutations in exons 1-12 and mutations leading to a premature stop codon lead to the severe form of the disease, while missense pathogenic variants in exons 13-17 lead to the mild form of the disease. Multidisciplinary team approach is recommended.

Seneca Valley Virus Exploits TEM8, a Collagen Receptor Implicated in Tumor Growth

Recent studies reveal that Seneca Valley Virus (SVV) exploits tumor endothelial marker 8 (TEM8) for cellular entry, the same surface receptor pirated by bacterial-derived anthrax toxin. This observation is particularly significant as SVV is a known oncolytic virus which selectively infects and kills tumor cells, particularly those of neuroendocrine origin. TEM8 is a transmembrane glycoprotein that is preferentially upregulated in some tumor cell and tumor-associated stromal cell populations. Both TEM8 and SVV have been evaluated for targeting of tumors of multiple origins, but the connection between the two was previously unknown. Here, we review currently understood interactions between TEM8 and SVV, anthrax protective antigen (PA), and collagen VI, a native binding partner of TEM8, with an emphasis on potential therapeutic directions moving forward.

The genetic basis of hyaline fibromatosis syndrome in patients from a consanguineous background: a case series

BACKGROUND

Hyaline fibromatosis syndrome (HFS) is a rare heritable multi-systemic disorder with significant dermatologic manifestations. It is caused by mutations in ANTXR2, which encodes a transmembrane receptor involved in collagen VI regulation in the extracellular matrix. Over 40 mutations in the ANTXR2 gene have been associated with cases of HFS. Variable severity of the disorder in different patients has been proposed to be related to the specific mutations in these patients and their location within the gene.

CASE PRESENTATION

In this report, we describe four cases of HFS from consanguineous backgrounds. Genetic analysis identified a novel homozygous frameshift deletion c.969del (p.Ile323Metfs*14) in one case, the previously reported mutation c.134 T > C (p.Leu45Pro) in another case, and the recurrent homozygous frameshift mutation c.1073dup (p.Ala359Cysfs*13) in two cases. The epidemiology of this latter mutation is of particular interest, as it is a candidate for inhibition of nonsense-mediated mRNA decay. Haplotype analysis was performed to determine the origin of this mutation in this consanguineous cohort, which suggested that it may develop sporadically in different populations.

CONCLUSIONS

This information provides insights on genotype-phenotype correlations, identifies a previously unreported mutation in ANTXR2, and improves the understanding of a recurrent mutation in HFS.

Capillary morphogenesis gene 2 maintains gastric cancer stem-like cell phenotype by activating a Wnt/β-catenin pathway

A growing body of evidence shows that the development and progression of gastric cancer (GC) is mainly associated to the presence of gastric cancer stem-like cells (GCSLCs). However, it is unclear how GCSLC population is maintained. This study aimed to explore the role of capillary morphogenesis gene 2 (CMG2) in GCSLC maintenance and the relevance to GC progression. We found that CMG2 was highly expressed in GC tissues and the expression levels were associated with the invasion depth and lymph node metastasis of GC, and inversely correlated with the survival of GC patients. Sorted CMG2^High GC cells preferentially clustered in CD44^High stem-like cell population, which expressed high levels of stemness-related genes with increased capabilities of self-renewal and tumorigenicity. Depletion of CMG2 gene resulted in reduction of GCSLC population with attenuated stemness and decrease of invasive and metastatic capabilities with subdued epithelial–mesenchymal transition phenotype in GC cells. Mechanistically, CMG2 interacted with LRP6 in GCSLCs to activate a Wnt/β-catenin pathway. Thus, our results demonstrate that CMG2 promotes GC progression by maintaining GCSLCs and can serve as a new prognostic indicator and a target for human GC therapy.

Collagen VI disorders: Insights on form and function in the extracellular matrix and beyond

Mutations in the three canonical collagen VI genes, COL6A1, COL6A2 and COL6A3, cause a spectrum of muscle disease from Bethlem myopathy at the mild end to the severe Ullrich congenital muscular dystrophy. Mutations can be either dominant or recessive and the resulting clinical severity is influenced by the way mutations impact the complex collagen VI assembly process. Most mutations are found towards the N-terminus of the triple helical collagenous domain and compromise extracellular microfibril assembly. Outside the triple helix collagen VI is highly polymorphic and discriminating mutations from rare benign changes remains a major diagnostic challenge. Collagen VI deficiency alters extracellular matrix structure and biomechanical properties and leads to increased apoptosis and oxidative stress, decreased autophagy, and impaired muscle regeneration. Therapies that target these downstream consequences have been tested in a collagen VI null mouse and also in small human trials where they show modest clinical efficacy. An important role for collagen VI in obesity, cancer and diabetes is emerging. A major barrier to developing effective therapies is the paucity of information about how collagen VI deficiency in the extracellular matrix signals the final downstream consequences - the receptors involved and the intracellular messengers await further characterization.

CMG2 Expression Is an Independent Prognostic Factor for Soft Tissue Sarcoma Patients

The capillary morphogenesis gene 2 (CMG2), also known as the anthrax toxin receptor 2 (ANTXR2), is a transmembrane protein putatively involved in extracellular matrix (ECM) adhesion and tissue remodeling. CMG2 promotes endothelial cell proliferation and exhibits angiogenic properties. Its downregulation is associated with a worsened survival of breast carcinoma patients. Aim of this study was to analyze the CMG2 mRNA and protein expression in soft tissue sarcoma and their association with patient outcome. CMG2 mRNA was measured in 121 tumor samples of soft tissue sarcoma patients using quantitative real-time PCR. CMG2 protein was evaluated in 52 tumor samples by ELISA. CMG2 mRNA was significantly correlated with the corresponding CMG2 protein expression (r_s = 0.31; p = 0.027). CMG2 mRNA expression was associated with the mRNA expressions of several ECM and tissue remodeling enzymes, among them CD26 and components of the uPA system. Low CMG2 mRNA expression was correlated with a worsened patients’ disease-specific survival in Kaplan-Meier analyses (mean patient survival was 25 vs. 96 months; p = 0.013), especially in high-stage tumors. A decreased CMG2 expression is a negative prognostic factor for soft tissue sarcoma patients. CMG2 may be an interesting candidate gene for the further exploration of soft tissue sarcoma genesis and progression.