Upregulation of Wilms' Tumor 1 in epicardial cells increases cardiac fibrosis in dystrophic mice

The Wilms' Tumor Suppressor WT1 in Cardiomyocytes: Implications for Cardiac Homeostasis and Repair

The Wilms' tumor suppressor WT1 is essential for the development of the heart, among other organs such as the kidneys and gonads. The Wt1 gene encodes a zinc finger transcription factor that regulates proliferation, cellular differentiation processes, and apoptosis. WT1 is also involved in cardiac homeostasis and repair. In adulthood, WT1-expression levels are lower compared to those observed through development, and WT1 expression is restricted to a few cell types. However, its systemic deletion in adult mice is lethal, demonstrating that its presence is also key for organ maintenance. In response to injury, the epicardium re-activates the expression of WT1, but little is known about the roles it plays in cardiomyocytes, which are the main cell type affected after myocardial infarction. The fact that cardiomyocytes exhibit a low proliferation rate in the adult heart in mammals highlights the need to explore new approaches for cardiac regeneration. The aim of this review is to emphasize the functions carried out by WT1 in cardiomyocytes in cardiac homeostasis and heart regeneration.

Novel biallelic variants in IREB2 cause an early-onset neurodegenerative disorder in a Chinese pedigree

BACKGROUND

Cellular iron metabolism is essential for maintaining various biological processes in organisms, and this is influenced by the function of iron-responsive element-binding protein 2 (IRP2), encoded by the IREB2 gene. Since 2019, three cases of a genetic neurodegenerative syndrome resulting from compound heterozygous mutations in IREB2 have been documented, highlighting the crucial role of IRP2 in regulating iron metabolism homeostasis. This study aims to investigate the molecular basis in a single proband born to non-consanguineous healthy parents, presenting with severe psychomotor developmental abnormalities and microcytic anemia.

METHODS

Trio-whole exome sequencing (WES) was applied to identify the disease-causing gene in an 8-month-old male patient from China. In silico tools were used to predict the pathogenicity of the identified variants, and in vitro functional studies were performed to evaluate the molecular mechanism.

RESULTS

WES identified novel biallelic variants, c.1111 A > G (P.Ile371Val) and c.2477 A > T (P.Asp826Val), in the IREB2 gene, which encodes the iron metabolism-related protein, IRP2. Functional studies revealed that c.2477 A > T resulted in a significant degradation of IRP2, which led to the misregulation of intracellular ferric iron.

CONCLUSIONS

We report the identification of the first functional domain associated with the degradation of IRP2. The biallelic variants that affect protein degradation likely underlie the pathogenesis of the IRP2-related neurodegenerative disorder. Moreover, the use of proteasome inhibitors can potentially restore the expression of IRP2, highlighting a promising therapeutic target for patients with IRP2deficiency.

A novel mutation in SMARCB1 associated with adult Coffin-Siris syndrome and meningioma

SMARCB1 encodes a core subunit of the SWI/SNF chromatin remodeling complex, which plays a crucial role in the regulation of gene expression. Germline mutations in the SMARCB1 gene have been linked to early childhood Coffin-Siris syndrome type 3 (CSS3), a rare congenital malformation syndrome characterized by severe developmental delay and intellectual disability. In this study, we report a family of two adult CSS3 patients with a novel missense SMARCB1 mutation (c.1091A>C, p.Lys364Thr) identified through whole-exome sequencing (WES). Both patients exhibit selective difficulties in verbal learning and experience language delays. Additionally, the development of meningioma is confirmed in one of the patients. Mechanistic studies suggest that this missense mutation may abnormally activate the MAPK signaling pathway, which is implicated in the pathogenesis of tumor progression and neurodevelopmental disorders. This is the first reported case of a germline mutation in the SMARCB1 gene associated with both CSS3 and meningioma, thereby expanding the phenotypic spectrum of SMARCB1-related disorders.

Histone modifications in Duchenne muscular dystrophy: pathogenesis insights and therapeutic implications

Duchenne muscular dystrophy (DMD) is a commonly encountered genetic ailment marked by loss-of-function mutations in the Dystrophin gene, ultimately resulting in progressive debilitation of skeletal muscle. The investigation into the pathogenesis of DMD has increasingly converged on the role of histone modifications within the broader context of epigenetic regulation. These modifications, including histone acetylation, methylation and phosphorylation, are catalysed by specific enzymes and play a critical role in gene expression. This article provides an overview of the histone modifications occurring in DMD and analyses the research progress and potential of different types of histone modifications in DMD due to changes in cellular signalling for muscle regeneration, to provide new insights into diagnostic and therapeutic options for DMD.

Obesity Management in Youth with Duchenne Muscular Dystrophy: A Review of Metformin and Alternative Pharmacotherapies

Background: Individuals with Duchenne muscular dystrophy (DMD) have increased risk of obesity from prolonged glucocorticoid use and progressive muscle weakness. Over 50% have obesity by the teenage years. Objectives: The current study examines literature on obesity management in DMD and describes how obesity pharmacotherapy can be used in this high-risk cohort. Methods: This review was conducted in adherence to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews checklist. A Pubmed Database search was conducted from January 2000 to May 2024. Included terms were DMD and topiramate, phentermine, metformin, glucagon-like peptide-1 receptor agonist, semaglutide, and liraglutide. Eligible studies were cataloged to examine obesity pharmacotherapy, side effect profiles, and clinical outcomes. Results: Twenty studies met inclusion criteria, 18 on metformin. Reviewed studies varied in duration from 4 to 24 weeks, ages 6.5-44 years old, with 112 participants total (range: 1-30 participants). Included studies were: eight animal studies, six clinical trials, four reviews, one cohort study, and one case report. Primary outcomes varied among studies: muscular degeneration and function (15 articles), cardiac function (2 articles), weight loss (2 articles), and general endocrine care (1 article). Conclusions: Adjunct obesity pharmacotherapy use in youth with DMD is promising but needs to be confirmed. Large gaps include appropriate agent selection, side effect monitoring, and dose escalation. The overall quality of pediatric-specific evidence for the use of obesity pharmacotherapy in youth with DMD is low. Future research is needed to investigate how to safely utilize these agents.

Duchenne muscular dystrophy: pathogenesis and promising therapies

Duchenne muscular dystrophy (DMD) is a severe, progressive, muscle-wasting disease, characterized by progressive deterioration of skeletal muscle that causes rapid loss of mobility. The failure in respiratory and cardiac muscles is the underlying cause of premature death in most patients with DMD. Mutations in the gene encoding dystrophin result in dystrophin deficiency, which is the underlying pathogenesis of DMD. Dystrophin-deficient myocytes are dysfunctional and vulnerable to injury, triggering a series of subsequent pathological changes. In this review, we detail the molecular mechanism of DMD, dystrophin deficiency-induced muscle cell damage (oxidative stress injury, dysregulated calcium homeostasis, and sarcolemma instability) and other cell damage and dysfunction (neuromuscular junction impairment and abnormal differentiation of muscle satellite). We also describe aberrant function of other cells and impaired muscle regeneration due to deterioration of the muscle microenvironment, and dystrophin deficiency-induced multiple organ dysfunction, while summarizing the recent advances in the treatment of DMD.

Fibrotic Scar in CNS Injuries: From the Cellular Origins of Fibroblasts to the Molecular Processes of Fibrotic Scar Formation

Central nervous system (CNS) trauma activates a persistent repair response that leads to fibrotic scar formation within the lesion. This scarring is similar to other organ fibrosis in many ways; however, the unique features of the CNS differentiate it from other organs. In this review, we discuss fibrotic scar formation in CNS trauma, including the cellular origins of fibroblasts, the mechanism of fibrotic scar formation following an injury, as well as the implication of the fibrotic scar in CNS tissue remodeling and regeneration. While discussing the shared features of CNS fibrotic scar and fibrosis outside the CNS, we highlight their differences and discuss therapeutic targets that may enhance regeneration in the CNS.