Soluble Heparin Binding Epidermal Growth Factor-Like Growth Factor Is a Regulator of GALGT2 Expression and GALGT2-Dependent Muscle and Neuromuscular Phenotypes

Duchenne muscular dystrophy: promising early-stage clinical trials to watch

INTRODUCTION

Current therapies are unable to cure Duchenne muscular dystrophy (DMD), a severe and common form of muscular dystrophy, and instead aim to delay disease progression. Several treatments currently in phase I trials could increase the number of therapeutic options available to patients.

AREAS COVERED

This review aims to provide an overview of current treatments undergoing or having recently undergone early-stage trials. Several exon-skipping and gene therapy approaches are currently being investigated at the clinical stage to address an unmet need for DMD treatments. This article also covers Phase I trials from the last 5 years that involve inhibitors, small molecules, a purified synthetic flavanol, a cell-based therapy, and repurposed cardiac or tumor medications.

EXPERT OPINION

With antisense oligonucleotide (AON) treatments making up the majority of conditionally approved DMD therapies, most of the clinical trials occurring within the last 5 years have also evaluated exon-skipping AONs. The approval of Elevidys, a micro-dystrophin therapy, is reflected in a recent trend toward gene transfer therapies in phase I DMD clinical trials, but their safety and efficacy are being established in this phase of development. Other Phase I clinical-stage approaches are diverse, but have a range in efficacy, safety, and endpoint measures.

Maternal-derived galectin-1 shapes the placenta niche through Sda terminal glycosylation: Implication for preeclampsia

Placental abnormalities cause impaired fetal growth and poor pregnancy outcome (e.g. preeclampsia [PE]) with long-lasting consequences for the mother and offspring. The molecular dialogue between the maternal niche and the developing placenta is critical for the function of this organ. Galectin-1 (gal-1), a highly expressed glycan-binding protein at the maternal-fetal interface, orchestrates the maternal adaptation to pregnancy and placenta development. Down-regulation or deficiency of gal-1 during pregnancy is associated with the development of PE; however, the maternal- and placental-derived gal-1 contributions to the disease onset are largely unknown. We demonstrate that lack of gal-1 imposes a risk for PE development in a niche-specific manner, and this is accompanied by a placental dysfunction highly influenced by the absence of maternal-derived gal-1. Notably, differential placental glycosylation through the Sda-capped N-glycans dominates the invasive trophoblast capacity triggered by maternal-derived gal-1. Our findings show that gal-1 derived from the maternal niche is essential for healthy placenta development and indicate that impairment of the gal-1 signaling pathway within the maternal niche could be a molecular cause for maternal cardiovascular maladaptation during pregnancy.

BPTF in bone marrow provides a potential progression biomarker regulated by TFAP4 through the PI3K/AKT pathway in neuroblastoma

BACKGROUND

Neuroblastoma (NB) is the most common extracranial malignant solid tumor in children, which is highly prone to bone marrow (BM) metastasis. BM can monitor early signs of mild disease and metastasis. Existing biomarkers are insufficient for the diagnosis and treatment of NB. Bromodomain PHD finger transcription factor (BPTF) is an important subunit of the chromatin-remodeling complex that is closely associated with tumors. Here, we evaluated whether BPTF in BM plays an important role in predicting NB progression, and explore the molecular mechanism of BPTF in NB.

METHODS

The clinical relevance of the BPTF was predicted in the GEO (GSE62564) and TARGET database. The biological function of BPTF in NB was investigated by constructing cell lines and employing BPTF inhibitor AU1. Western blot was used to determine the changes of BPTF, TFAP4, PI3K/AKT signaling and Epithelial-mesenchymal transition (EMT) related markers. A total of 109 children with newly diagnosed NB in Beijing Children's Hospital from January 2018 to March 2021 were included in this study. RT-PCR was used to measure the BPTF and TFAP4 expression in BM. The cut-off level was set at the median value of BPTF expression levels.

RESULTS

Databases suggested that BPTF expression was higher in NB and was significantly associated with stage and grade. Proliferation and migration of NB cells were slowed down when BPTF was silenced. Mechanistically, TFAP4 could positively regulate BPTF and promotes EMT process through activating the PI3K/AKT signaling pathway. Moreover, detection of the newly diagnosed BM specimens showed that BPTF expression was significantly higher in high-risk group, stage IV group and BM metastasis group. Children with high BPTF at initial diagnosis were considered to have high risk for disease progression and recurrence. BPTF is an independent risk factor for predicting NB progression.

CONCLUSIONS

A novel and convenient BPTF-targeted humoral detection that can prompt minimal residual and predict NB progression in the early stages of the disease were identified. BPTF inhibitor AU1 is expected to become a new targeted drug for NB therapy. It's also reveal previously unknown mechanisms of BPTF in NB cell proliferation and metastasis through TFAP4 and PI3K/AKT pathways.

The story of the Sda antigen and of its cognate enzyme B4GALNT2: What is new?

The structure Siaα2,3(GalNAcβ1,4)Gal- is the epitope of the Sd^a antigen, which is expressed on the erythrocytes and secretions of the vast majority of Caucasians, carried by N- and O-linked chains of glycoproteins, as well as by glycolipids. Sd^a is very similar, but not identical, to ganglioside GM2 [Siaα2,3(GalNAcβ1,4)Galβ1,4Glc-Cer]. The Sd^a synthase β1,4 N-acetylgalactosaminyl transferase 2 (B4GALNT2) exists in a short and a long form, diverging in the aminoterminal domain. The latter has a very long cytoplasmic tail and displays a Golgi- as well as a post-Golgi localization. The biosynthesis of Sd^a is mutually exclusive with that of the cancer-associated sialyl Lewis antigens, whose structure is Siaα2,3Galβ1,3/4(Fucα1,4/3)GlcNAc-. B4GALNT2 is down-regulated in colon cancer but patients with higher expression survive longer. In experimental systems, B4GALNT2 inhibits colon cancer progression,not only through inhibition of sialyl Lewis antigen biosynthesis. By contrast, in breast cancer B4GALNT2 is associated with malignancy. In colon cancer, the B4GALNT2 gene is regulated by multiple mechanisms, which include miRNA and transcription factor expression, as well as CpG methylation. In addition, Sd^a/B4GALNT2 regulates the susceptibility to infectious agents, the protection from muscle dystrophy, the activity of immune system in pregnancy and the immune rejection in xenotransplantation.

The Cancer-Associated Antigens Sialyl Lewisa/x and Sda: Two Opposite Faces of Terminal Glycosylation

Simple Summary

The glycosyltransferase β1,4-N-acetylgalactosaminyltransferae 2 (B4GALNT2), product of the B4GALNT2 gene is responsible for the biosynthesis of the carbohydrate antigen Sd^a. Both the enzyme and its cognate antigen display a restricted pattern of tissue expression and modulation in colorectal, gastric, and mammary cancers. In colorectal cancer, B4GALNT2 is generally downregulated, but patients displaying higher expression survive longer. The sialyl Lewis^a and sialyl Lewis^x antigens are associated with malignancy. Their biosynthesis and that of Sd^a are mutually exclusive. Forced expression of B4GALNT2 in colorectal cancer cell lines modulates the transcriptome towards lower malignancy, reducing stemness. These effects are independent of B4GALNT2-induced sLe^a/sLe^x inhibition. Thus, B4GALNT2 is a marker of better prognosis and a cancer-restraining enzyme in colorectal cancer, with a therapeutic potential.

Abstract

Terminal carbohydrate structures are particularly relevant in oncology because they can serve as cancer markers and alter the phenotype of cancer cells. The Sd^a antigen and the sialyl Lewis^x and sialyl Lewis^a (sLe^x and sLe^a) antigens are terminal structures whose biosynthesis is mutually exclusive. In this review, we describe the main features of the Sd^a antigen in cancer and its relationship with sLe^x/a antigens. Information was obtained from an extensive literature search and from The Cancer Genome Atlas (TCGA) public database. The Sd^a biosynthetic enzyme B4GALNT2 undergoes downregulation in colorectal (CRC) and stomach cancer, while it is ectopically expressed by a minority of breast cancer (BRCA) patients. High expression of B4GALNT2 is associated with better prognosis and a less malignant gene expression profile in CRC, while the opposite occurs in BRCA. The regulation of B4GALNT2 expression in CRC is multifactorial, involving gene methylation and miRNA expression. Forced expression of B4GALNT2 inhibited sLe^a/sLe^x and reduced malignancy and stemness in cells constitutively expressing sLe^x/a antigens. However, consistent effects were observed upon B4GALNT2 forced expression and in cells not expressing sLe^x/a antigens. Thus, B4GALNT2 and the Sd^a antigen exert a tumor-restraining activity in CRC and probably other gastrointestinal cancers, independently of sLe^x/a antigens.

Integrative ATAC-seq and RNA-seq Analysis of the Longissimus Muscle of Luchuan and Duroc Pigs

Luchuan pig is a typical obese pig breed in China, and the diameter and area of its longissimus dorsi muscle fibers are significantly smaller than those of Duroc (lean) pig. Skeletal muscle fiber characteristics are related to meat quality of livestock. There is a significant correlation between the quality of different breeds of pork and the characteristics of muscle fiber, which is an important factor affecting the quality of pork. The diameter and area of muscle fibers are related to muscle growth and development. Therefore, we used the assay for transposase-accessible chromatin using sequencing (ATAC-seq) and RNA sequencing (RNA-seq) analysis to investigate the potential mechanism underlying the difference in skeletal muscle growth and development between the two types of pigs. First, transposase-accessible chromatin was analyzed to map the landscape of open chromatin regions and transcription factor binding sites. We identified several transcription factors that potentially affected muscle growth and development, including TFAP4, MAX, NHLH1, FRX5, and TGIF1. We also found that transcription factors with basic helix-loop-helix structures had a preference for binding to genes involved in muscle development. Then, by integrating ATAC-seq and RNA-seq, we found that the Wnt signaling pathway, the mTOR signaling pathway, and other classical pathways regulate skeletal muscle development. In addition, some pathways that might regulate skeletal muscle growth, such as parathyroid hormone synthesis, secretion, and action, synthesis and degradation of ketone bodies, and the thyroid hormone signaling pathway, which were significantly enriched. After further study, we identified a number of candidate genes (ASNS, CARNS1, G0S2, PPP1R14C, and SH3BP5) that might be associated with muscle development. We also found that the differential regulation of chromatin openness at the level of some genes was contrary to the differential regulation at the level of transcription, suggesting that transcription factors and transcriptional repressors may be involved in the regulation of gene expression. Our study provided an in-depth understanding of the mechanism behind the differences in muscle fibers from two species of pig and provided an important foundation for further research on improving the quality of pork.

Serum Amphiregulin and Heparin-Binding Epidermal Growth Factor as Biomarkers in Patients with Idiopathic Inflammatory Myopathy

Background. The epidermal growth factors amphiregulin (AREG) and heparin-binding epidermal growth factor (HB-EGF) are implicated in the pathogenesis of several autoimmune diseases, but their clinical and pathological roles in idiopathic inflammatory myopathy (IIM) are unclear. Methods. Serum AREG and HB-EGF levels were measured by ELISA in patients with IIM (n = 37), systemic sclerosis (n = 17), and rheumatoid arthritis (n = 10), and for seven age- and sex-matched healthy controls (HCs). Associations between serum AREG or HB-EGF levels and the clinical parameters were analyzed. Results. Serum AREG levels in IIM patients were significantly elevated compared to those in HCs (median, 20.7 and 10.7 pg/mL, respectively; p = 0.025). In particular, serum AREG levels in IIM patients with interstitial lung disease (ILD) were higher than those of HCs (22.4 pg/mL, p = 0.027). The disease duration in patients with elevated serum AREG levels was significantly shorter compared to those who had normal serum AREG levels (7 and 21 months, respectively; p = 0.0012). Serum HB-EGF levels were significantly increased in IIM patients with elevated CK levels (136.2 pg/mL; p = 0.020) and patients with anti-Mi-2 antibody (183.7 pg/mL; p = 0.045) compared to those in HCs (74.9 pg/mL). Conclusion. These results suggested that AREG could be a promising biomarker associated with early-phase IIM-related ILD, and that HB-EGF expression was associated with muscle injury and regeneration in IIM.

Utrophin modulator drugs as potential therapies for Duchenne and Becker muscular dystrophies

Utrophin is an autosomal paralogue of dystrophin, a protein whose deficit causes Duchenne and Becker muscular dystrophies (DMD/BMD). Utrophin is naturally overexpressed at the sarcolemma of mature dystrophin‐deficient fibres in DMD and BMD patients as well as in the mdx Duchenne mouse model. Dystrophin and utrophin can co‐localise in human foetal muscle, in the dystrophin‐competent fibres from DMD/BMD carriers, and revertant fibre clusters in biopsies from DMD patients. These findings suggest that utrophin overexpression could act as a surrogate, compensating for the lack of dystrophin, and, as such, it could be used in combination with dystrophin restoration therapies. Different strategies to overexpress utrophin are currently under investigation. In recent years, many compounds have been reported to modulate utrophin expression efficiently in preclinical studies and ameliorate the dystrophic phenotype in animal models of the disease. In this manuscript, we discuss the current knowledge on utrophin protein and the different mechanisms that modulate its expression in skeletal muscle. We also include a comprehensive review of compounds proposed as utrophin regulators and, as such, potential therapeutic candidates for these muscular dystrophies.

Micro-laminin gene therapy can function as an inhibitor of muscle disease in the dyW mouse model of MDC1A

Gene replacement for laminin-α2-deficient congenital muscular dystrophy 1A (MDC1A) is currently not possible using a single adeno-associated virus (AAV) vector due to the large size of the LAMA2 gene. LAMA2 encodes laminin-α2, a subunit of the trimeric laminin-211 extracellular matrix (ECM) protein that is the predominant laminin expressed in skeletal muscle. LAMA2 expression stabilizes skeletal muscle, in part by binding membrane receptors via its five globular (G) domains. We created a small, AAV-deliverable, micro-laminin gene therapy that expresses these G1-5 domains, LAMA2(G1-5), to test their therapeutic efficacy in the dy^W mouse model for MDC1A. We also fused the heparin-binding (HB) domain from HB epidermal growth factor-like growth factor (HB-EGF) to LAMA2(G1-5) to test whether this would increase muscle ECM expression. dy^W mice treated intravenously with rAAV9.CMV.HB-LAMA2(G1-5) showed increased muscle ECM expression of transgenic protein relative to mice treated with rAAV9.CMV.LAMA2(G1-5) and showed improved weight-normalized forelimb grip strength relative to untreated dy^W mice. Additionally, dy^W muscle fibers expressing either micro-laminin protein showed some measures of reduced pathology, although levels of muscle cell apoptosis and inflammation were not decreased. Although systemic expression of rAAV9.CMV.HB-LAMA2(G1-5) did not inhibit all disease phenotypes, these studies demonstrate the feasibility of using a micro-laminin gene therapy strategy to deliver gene replacement for MDC1A.

The Flot2 component of the lipid raft changes localization during neural differentiation of P19C6 cells

Background

Flotillin-2 (Flot2) is a lipid raft scaffold protein that is thought to be related to neural differentiation. Flot2 is phosphorylated by Fyn, a Src kinase, and causes raft-dependent endocytosis; however, the exact role of Flot2 in neural differentiation remains unclear. To reveal the roles of lipid raft-associated proteins during neural differentiation, we tried to analyze the expression and localization.

Results

In this study, we found that the expression levels of the Flot2 and Fyn proteins increased in whole-cell lysates of P19C6 cells after neural differentiation. In addition, sucrose density fractionation and immunofluorescence experiments revealed an increase in the localization of Flot2 and Fyn to lipid rafts after neural differentiation. We also found that Fyn partially colocalized with Flot2 lipid rafts in neural cells.

Conclusion

The observed distribution of Fyn and level of inactivated Fyn and/or c-Src in detergent–resistant membrane (DRM) fractions suggests that the amount of activated Fyn might increase in DRM fractions after neural differentiation. Overall these findings suggest that Flot2 lipid rafts are associated with Fyn, and that Fyn phosphorylates Flot2 during neural differentiation of P19C6 cells.

Electronic supplementary material

The online version of this article (10.1186/s12860-019-0225-0) contains supplementary material, which is available to authorized users.