A Mouse Model of Glycogen Storage Disease Type IX-Beta: A Role for Phkb in Glycogenolysis

Exploring the heterogeneity of osteosarcoma cell characteristics and metabolic states and their association with clinical prognosis

Background

Osteosarcoma is a malignant tumor originating from mesenchymal bone tissue, characterized by high malignancy and poor prognosis. Despite progress in comprehensive treatment approaches, the five-year survival rate remains largely unchanged, highlighting the need to clarify its underlying mechanisms and discover new therapeutic targets.

Methods

This study utilized RNA sequencing data from multiple public databases, encompassing osteosarcoma samples and healthy controls, along with single-cell RNA sequencing data. Various methods were utilized, such as differential expression analysis of genes, analysis of metabolic pathways, and weighted gene co-expression network analysis (WGCNA), to pinpoint crucial genes. Using this list of genes, we developed and validated a prognostic model that incorporated risk signatures, and we evaluated the effectiveness of the model through survival analysis, immune cell infiltration examination, and drug sensitivity evaluation.

Results

We analyzed gene expression and metabolic pathways in nine samples using single-cell sequencing data. Initially, we performed quality control and clustering, identifying 21 statistically significant cell subpopulations. Metabolic analyses of these subpopulations revealed heterogeneous activation of metabolic pathways. Focusing on the osteoblastic cell subpopulation, we further subdivided it into six groups and examined their gene expression and differentiation capabilities. Differential expression and enrichment analyses indicated that tumor tissues were enriched in cytoskeletal and structural pathways. Through WGCNA, we identified core genes negatively correlated with four highly activated metabolic pathways. Using osteosarcoma patient data, we developed a risk signature model that demonstrated robust prognostic predictions across three independent cohorts. Ultimately, we performed a thorough examination of the model, which encompassed clinical and pathological characteristics, enrichment analysis, pathways associated with cancer markers, and scores of immune infiltration, highlighting notable and complex disparities between high-risk and low-risk populations.

Conclusion

This research clarifies the molecular mechanisms and metabolic features associated with osteosarcoma and how they relate to patient outcomes, offering novel perspectives and approaches for targeted therapy and prognostic assessment in osteosarcoma.

Progressive liver disease and dysregulated glycogen metabolism in murine GSD IX γ2 models human disease

Hepatic glycogen storage disease type IX γ2 (GSD IX γ2) is a severe, liver-specific subtype of GSD IX. While all patients with hepatic GSD IX present with similar symptoms, over 95 % of patients with GSD IX γ2 progress to liver fibrosis and cirrhosis. Despite disease severity, the long-term natural history of GSD IX γ2 liver disease progression is not known. Our lab previously characterized the Phkg2-/- mouse model at 3 months of age, demonstrating that the mouse recapitulates the early liver disease phenotype of GSD IX γ2. To understand how liver disease progresses in GSD IX γ2, we characterized the mouse model through 24 months of age. Our study showed for the first time that GSD IX γ2 mice develop liver fibrosis that progresses to cirrhosis. Importantly, we observed that the progression of liver fibrosis is associated with an initial elevation and subsequent decrease of key GSD biomarkers - the latter being a finding that is often considered to be an improvement of disease in patients. In recognition of the unique liver fibrosis pattern and to support future therapeutic investigations using this model, we developed a novel scoring system for GSD IX γ2 mouse liver pathology. Lastly, this work introduces evidence of a dysregulated glycogen metabolism pathway which can serve as an endpoint for future therapeutic evaluation. As we await longitudinal clinical natural history data, these findings greatly expand our understanding of liver disease manifestations in GSD IX γ2 and have notable clinical applications.

Genotypic and phenotypic features of 39 Chinese patients with glycogen storage diseases type I, VI, and IX

Glycogen storage diseases (GSDs) are abnormally inherited glycogen metabolism mainly affecting the liver, muscles, and heart. Deficiency of proteins involved in glycogen metabolism caused by genetic mutations are responsible for different subtype of GSDs. However, there are still some challenges in diagnosing GSD. This study includes 39 suspected GSDs patients from unrelated families in China. Next-generation sequencing (NGS) was used to investigate the reason for their diseases at the genetic level. Finally, all 39 patients were diagnosed with GSDs, including 20 GSD-Ia, 4 GSD-VI, and 15 GSD IX (12 GSD-IXa patients and 3 GSD-IXb patients). Thirty-two mutations in G6PC1, PYGL, PHKA2, and PHKB genes were identified, with 14 of them being novel variants. The pathogenicity of novel variants was classified according to ACMG guildlines and predicted by in slico algorithms. Mutations p.L216L and p.R83H in G6PC1 gene may be the hot spot mutation in Chinese. Hearing impairment is a rare clinical feature of GSD Ia, which has also been observed in our cohort. The severity of GSD VI and IX was indicated by our patients. Close follow-up should be applied to GSD VI and IX patients. Our findings provided evidence for building the phenotype-genotype of GSDs and expanded the mutation spectrum of related genes.

Change and pathological significance of glycogen content in oral squamous cell carcinoma and oral submucous fibrosis

OBJECTIVE

This study aimed to investigate the change and pathological significance of glycogen content in oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF).

METHODS AND MATERIALS

13 normal oral mucosa (NOM), 12 OSF mucosa, and 35 pairs of OSCC tissues and their corresponding adjacent mucosa tissues (AT) were collected from Xiangya Hospital for PAS staining to detect glycogen. Transcriptome sequencing data from OSCC were used to compare glycogen metabolism gene expression differences. Kaplan-Meier method was conducted to estimate Recurrence-free survival (RFS).

RESULTS

Glycogen levels were lower in OSF than in NOM and lower in OSCC than in AT. Transcriptome sequencing data analysis showed the expression of most glycogenolysis genes was increased and the expression of glycogen synthesis genes including PPP1R3C and GBE1 was decreased in OSCC tissues. High glycogen level was correlated with poor prognosis in OSCC patients under the background of OSF.

CONCLUSION

Glycogen may be used as a potential diagnostic biomolecule for OSF and OSCC, as well as a potential prognostic factor for OSCC in the context of OSF.

Ubiquitination plays an important role during the formation of chicken primordial germ cells

As an important posttranslational modification, ubiquitination plays an important role in regulating protein homeostasis in eukaryotic cells. In our previous studies, both the transcriptome and proteome suggested that ubiquitination is involved in the formation of chicken primordial germ cells (PGCs). Here, affinity enrichment combined with liquid chromatography-tandem mass spectrometry (MS/MS) was used to analyze the ubiquitome during the differentiation from embryonic stem cells to PGCs, and we identify that 724 lysine ubiquitinated sites were up-regulated in 558 proteins and 138 lysine ubiquitinated sites were down-regulated in 109 proteins. Furthermore, GO and KEGG enrichment analysis showed that ubiquitination regulates key proteins to participate in the progression of key events related to PGC formation and the transduction of key signals such as Wnt, MAPK, and insulin signals, followed by the detailed explanation of the specific regulatory mechanism of ubiquitination through the combined proteome and ubiquitome analysis. Moreover, both the activation and inhibition of neddylation were detrimental to the maintenance of the biological characteristics of PGCs, which also verified the importance of ubiquitination. In conclusion, this study provides a global view of the ubiquitome during the formation of PGCs by label-free quantitative ubiquitomics, which lays a theoretical foundation for the formation mechanism and specific application of chicken PGCs.

Gene therapy for glycogen storage diseases

Glycogen storage disorders (GSDs) are inherited disorders of metabolism resulting from the deficiency of individual enzymes involved in the synthesis, transport, and degradation of glycogen. This literature review summarizes the development of gene therapy for the GSDs. The abnormal accumulation of glycogen and deficiency of glucose production in GSDs lead to unique symptoms based upon the enzyme step and tissues involved, such as liver and kidney involvement associated with severe hypoglycemia during fasting and the risk of long-term complications including hepatic adenoma/carcinoma and end stage kidney disease in GSD Ia from glucose-6-phosphatase deficiency, and cardiac/skeletal/smooth muscle involvement associated with myopathy +/- cardiomyopathy and the risk for cardiorespiratory failure in Pompe disease. These symptoms are present to a variable degree in animal models for the GSDs, which have been utilized to evaluate new therapies including gene therapy and genome editing. Gene therapy for Pompe disease and GSD Ia has progressed to Phase I and Phase III clinical trials, respectively, and are evaluating the safety and bioactivity of adeno-associated virus vectors. Clinical research to understand the natural history and progression of the GSDs provides invaluable outcome measures that serve as endpoints to evaluate benefits in clinical trials. While promising, gene therapy and genome editing face challenges with regard to clinical implementation, including immune responses and toxicities that have been revealed during clinical trials of gene therapy that are underway. Gene therapy for the glycogen storage diseases is under development, addressing an unmet need for specific, stable therapy for these conditions.