Muscle Enriched Lamin Interacting Protein (Mlip) Binds Chromatin and Is Required for Myoblast Differentiation

Molecular composition of skeletal muscle in infants and adults: a comparative proteomic and transcriptomic study

To gain a deeper understanding of skeletal muscle function in younger age and aging in elderly, identification of molecular signatures regulating these functions under physiological conditions is needed. Although molecular studies of healthy muscle have been conducted on adults and older subjects, there is a lack of research on infant muscle in terms of combined morphological, transcriptomic and proteomic profiles. To address this gap of knowledge, we performed RNA sequencing (RNA-seq), tandem mass spectrometry (LC-MS/MS), morphometric analysis and assays for mitochondrial maintenance in skeletal muscle biopsies from both, infants aged 4-28 months and adults aged 19-65 years. We identified differently expressed genes (DEGs) and differentially expressed proteins (DEPs) in adults compared to infants. The down-regulated genes in adults were associated with functional terms primarily related to sarcomeres, cellular maintenance, and metabolic, immunological and developmental processes. Thus, our study indicates age-related differences in the molecular signatures and associated functions of healthy skeletal muscle. Moreover, the findings assert that processes previously associated solely with aging are indeed part of development and healthy aging. Hence, combined findings of this study also indicate that age-dependent controls are crucial in muscle disease studies, as otherwise the comparative results may not be reliable.

MLIP and Its Potential Influence on Key Oncogenic Pathways

Muscle-enriched A-type lamin-interacting protein (MLIP) is an emerging protein involved in cellular homeostasis and stress adaptation. Eukaryotic cells regulate various cellular processes, including metabolism, DNA repair, and cell cycle progression, to maintain cellular homeostasis. Disruptions in this homeostasis can lead to diseases such as cancer, characterized by uncontrolled cell growth and division. This review aims to explore for the first time the unique role MLIP may play in cancer development and progression, given its interactions with the PI3K/Akt/mTOR pathway, p53, MAPK9, and FOXO transcription factors, all critical regulators of cellular homeostasis and tumor suppression. We discuss the current understanding of MLIP's involvement in pro-survival pathways and its potential implications in cancer cells' metabolic remodeling and dysregulated homeostasis. Additionally, we examine the potential of MLIP as a novel therapeutic target for cancer treatment. This review aims to shed light on MLIP's potential impact on cancer biology and contribute to developing innovative therapeutic strategies.

MicroRNA205: A Key Regulator of Cardiomyocyte Transition from Proliferative to Hypertrophic Growth in the Neonatal Heart

The mammalian myocardium grows rapidly during early development due to cardiomyocyte proliferation, which later transitions to cell hypertrophy to sustain the heart's postnatal growth. Although this cell transition in the postnatal heart is consistently preserved in mammalian biology, little is known about the regulatory mechanisms that link proliferation suppression with hypertrophy induction. We reasoned that the production of a micro-RNA(s) could serve as a key bridge to permit changes in gene expression that control the changed cell fate of postnatal cardiomyocytes. We used sequential expression analysis to identify miR205 as a micro-RNA that was uniquely expressed at the cessation of cardiomyocyte growth. Cardiomyocyte-specific miR205 deletion animals showed a 35% increase in heart mass by 3 months of age, with commensurate changes in cell cycle and Hippo pathway activity, confirming miR205's potential role in controlling cardiomyocyte proliferation. In contrast, overexpression of miR205 in newborn hearts had little effect on heart size or function, indicating a complex, probably redundant regulatory system. These findings highlight miR205's role in controlling the shift from cardiomyocyte proliferation to hypertrophic development in the postnatal period.

MLIP-Associated Myopathy: A Case Report and Review of the Literature

BACKGROUND

Muscular A-type lamin-interacting protein (MLIP) has a regulatory role in myoblast differentiation and organization of myonuclear positioning in skeletal muscle. It is ubiquitously expressed but abundantly in cardiac, skeletal, and smooth muscles. Recently, two studies confirmed the causation of biallelic pathogenic variants in the MLIP gene of a novel myopathy phenotype.

OBJECTIVE

Description of the phenotypic spectrum and features of MLIP-related myopathy.

METHODS

report a patient with biallelic variants in MLIP gene with the clinical features, and histomorphological findings of MLIP-related myopathy and provide a literature review of the previously reported 12 patients.

RESULTS

MLIP-related myopathy is characterized by episodes of rhabdomyolysis, myalgia triggered by mild to moderate exercise, mild muscle weakness, and sometimes cardiac involvement characterized by cardiomyopathy and cardiac rhythm abnormalities.

CONCLUSIONS

This report reviews and extends the clinical features of a novel myopathy caused by biallelic pathogenic variants in the MLIP gene.

Recent advances in our understanding of genetic rhabdomyolysis

PURPOSE OF REVIEW

This review summarizes recent advances in our understanding of the genetics of rhabdomyolysis.

RECENT FINDINGS

Rhabdomyolysis is the acute breakdown of myofibres resulting in systemic changes that can be life-threatening. Environmental triggers, including trauma, exercise, toxins and infections, and/or gene defects can precipitate rhabdomyolysis. A schema (aptly titled RHABDO) has been suggested for evaluating whether a patient with rhabdomyolysis is likely to harbour an underlying genetic defect. It is becoming increasingly recognized that defects in muscular dystrophy and myopathy genes can trigger rhabdomyolysis, even as the sole or presenting feature. Variants in genes not previously associated with human disease have been identified recently as causative of rhabdomyolysis, MLIP , MYH1 and OBSCN . Our understanding of the pathomechanisms contributing to rhabdomyolysis have also improved with an increased awareness of the role of mitochondrial dysfunction in LPIN1 , FDX2 , ISCU and TANGO2 -mediated disease.

SUMMARY

An accurate genetic diagnosis is important for optimal clinical management of the patient, avoiding associated triggers and genetic counselling and cascade screening. Despite recent advances in our understanding of the genetics contributing to rhabdomyolysis, many patients remain without an accurate genetic diagnosis, suggesting there are many more causative genes, variants and disease mechanisms to uncover.

Identification of Five Cytotoxicity-Related Genes Involved in the Progression of Triple-Negative Breast Cancer

Background: Breast cancer is one of the deadly tumors in women, and its incidence continues to increase. This study aimed to identify novel therapeutic molecules using RNA sequencing (RNA-seq) data of breast cancer from our hospital. Methods: 30 pairs of human breast cancer tissue and matched normal tissue were collected and RNA sequenced in our hospital. Differentially expressed genes (DEGs) were calculated with raw data by the R package "edgeR", and functionally annotated using R package "clusterProfiler". Tumor-infiltrating immune cells (TIICs) were estimated using a website tool TIMER 2.0. Effects of key genes on therapeutic efficacy were analyzed using RNA-seq data and drug sensitivity data from two databases: the Cancer Cell Line Encyclopedia (CCLE) and the Cancer Therapeutics Response Portal (CTRP). Results: There were 2,953 DEGs between cancerous and matched normal tissue, as well as 975 DEGs between primary breast cancer and metastatic breast cancer. These genes were primarily enriched in PI3K-Akt signaling pathway, calcium signaling pathway, cAMP signaling pathway, and cell cycle. Notably, CD8⁺ T cell, M0 macrophage, M1 macrophage, regulatory T cell and follicular helper T cell were significantly elevated in cancerous tissue as compared with matched normal tissue. Eventually, we found five genes (GALNTL5, MLIP, HMCN2, LRRN4CL, and DUOX2) were markedly corelated with CD8⁺ T cell infiltration and cytotoxicity, and associated with therapeutic response. Conclusion: We found five key genes associated with tumor progression, CD8⁺ T cell and therapeutic efficacy. The findings would provide potential molecular targets for the treatment of breast cancer.

MLIP causes recessive myopathy with rhabdomyolysis, myalgia and baseline elevated serum creatine kinase

Striated muscle needs to maintain cellular homeostasis in adaptation to increases in physiological and metabolic demands. Failure to do so can result in rhabdomyolysis. The identification of novel genetic conditions associated with rhabdomyolysis helps to shed light on hitherto unrecognized homeostatic mechanisms. Here we report seven individuals in six families from different ethnic backgrounds with biallelic variants in MLIP, which encodes the muscular lamin A/C-interacting protein, MLIP. Patients presented with a consistent phenotype characterized by mild muscle weakness, exercise-induced muscle pain, variable susceptibility to episodes of rhabdomyolysis, and persistent basal elevated serum creatine kinase levels. The biallelic truncating variants were predicted to result in disruption of the nuclear localizing signal of MLIP. Additionally, reduced overall RNA expression levels of the predominant MLIP isoform were observed in patients' skeletal muscle. Collectively, our data increase the understanding of the genetic landscape of rhabdomyolysis to now include MLIP as a novel disease gene in humans and solidifies MLIP's role in normal and diseased skeletal muscle homeostasis.

Another step towards defining the genetic landscape of rhabdomyolysis

This scientific commentary refers to ‘MLIP causes recessive myopathy with rhabdomyolysis, myalgia and baseline high serum creatine kinase’, by Lopes Abath Neto et al. (doi:10.1093/brain/awab275).