Long non-coding RNA H19X as a regulator of mononuclear cell adhesion to the endothelium in systemic sclerosis

OBJECTIVE

To define the functional relevance of H19 X-linked co-expressed lncRNA (H19X) in endothelial cell (EC) activation as a key process in systemic sclerosis (SSc) vasculopathy.

METHODS

H19X expression in SSc skin biopsies was analyzed from single cell RNA sequencing (scRNA-seq) data. Differential expression and pathway enrichment analysis between cells expressing (H19Xpos) and non expressing H19X (H19Xneg) cells was performed. H19X function was investigated in human dermal microvascular EC (HDMECs) by silencing. H19X and EC adhesion molecules levels were analyzed by RT-qPCR and Western Blot after stimulation with proinflammatory cytokines. Cytoskeletal rearrangements were analyzed by fluorescent staining. Endothelial adhesion was evaluated by co-culture of HDMECs and fluorescent labelled peripheral blood mononuclear cells (PBMCs). Shedding VCAM1 was evaluated by ELISA on HDMEC supernatant.

RESULTS

scRNA-seq showed significant upregulation of H19X in SSc compared with healthy EC. In HDMEC, H19X was consistently induced by type I and II interferons. H19X knockdown lead to a significant decrease of the mRNA of several adhesion molecules. Particularly, vascular cell adhesion protein 1 (VCAM1) was significantly reduced at protein and mRNA levels. Co-expression analysis of the scRNA-seq data confirmed a higher expression of VCAM1 in (H19Xpos) EC. EC were also strongly associated with the 'cell adhesion molecule' pathway. Moreover, VCAM1 downstream pathway displayed less activation following H19X knockdown. Contractility of HDMEC, PBMC adhesion to HDMEC and VCAM1 shedding were also reduced following H19X knockdown.

CONCLUSIONS

lncRNA H19X may contribute to EC activation in SSc vasculopathy, acting as a regulator of expression of adhesion molecules in EC.

H19X-encoded miR-322(424)/miR-503 regulates muscle mass by targeting translation initiation factors

BACKGROUND

Skeletal muscle atrophy is a debilitating complication of many chronic diseases, disuse conditions, and ageing. Genome-wide gene expression analyses have identified that elevated levels of microRNAs encoded by the H19X locus are among the most significant changes in skeletal muscles in a wide scope of human cachectic conditions. We have previously reported that the H19X locus is important for the establishment of striated muscle fate during embryogenesis. However, the role of H19X-encoded microRNAs in regulating skeletal mass in adults is unknown.

METHODS

We have created a transgenic mouse strain in which ectopic expression of miR-322/miR-503 is driven by the skeletal muscle-specific muscle creatine kinase promoter. We also used an H19X mutant mouse strain in which transcription from the locus is interrupted by a gene trap. Animal phenotypes were analysed by standard histological methods. Underlying mechanisms were explored by using transcriptome profiling and validated in the two animal models and cultured myotubes.

RESULTS

Our results demonstrate that the levels of H19X microRNAs are inversely related to postnatal skeletal muscle growth. Targeted overexpression of miR-322/miR-503 impeded skeletal muscle growth. The weight of gastrocnemius muscles of transgenic mice was only 54.5% of the counterparts of wild-type littermates. By contrast, interruption of transcription from the H19X locus stimulates postnatal muscle growth by 14.4-14.9% and attenuates the loss of skeletal muscle mass in response to starvation by 12.8-21.0%. Impeded muscle growth was not caused by impaired IGF1/AKT/mTOR signalling or a hyperactive ubiquitin-proteasome system, instead accompanied by markedly dropped abundance of translation initiation factors in transgenic mice. miR-322/miR-503 directly targets eIF4E, eIF4G1, eIF4B, eIF2B5, and eIF3M.

CONCLUSIONS

Our study illustrates a novel pathway wherein H19X microRNAs regulate skeletal muscle growth and atrophy through regulating the abundance of translation initiation factors, thereby protein synthesis. The study highlights how translation initiation factors lie at the crux of multiple signalling pathways that control skeletal muscle mass.

Coregulatory long non-coding RNA and protein-coding genes in serum starved cells

Serum starvation is widely used in cell biology to trigger cell cycle arrest, apoptosis, autophagy, and metabolic adaptations. Serum starvation-related molecular events have been well characterized at protein level but not at transcript level: how long non-coding RNAs contribute to the regulation of protein-coding genes is largely unknown. Here, we captured the lncRNA transcriptome in serum starved mouse embryonic fibroblasts and identified three main modes of action: cis-acting/coregulatory, trans-acting, and "miRNA-carrier". Whole-genome and individual gene level analyses support that our annotation provides an important platform for understanding lncRNA/protein-coding gene coregulatory mechanisms in serum starvation.

H19X-encoded miR-424(322)/-503 cluster: emerging roles in cell differentiation, proliferation, plasticity and metabolism

miR-424(322)/-503 are mammal-specific members of the extended miR-15/107 microRNA family. They form a co-expression network with the imprinted lncRNA H19 in tetrapods. miR-424(322)/-503 regulate fundamental cellular processes including cell cycle, epithelial-to-mesenchymal transition, hypoxia and other stress response. They control tissue differentiation (cardiomyocyte, skeletal muscle, monocyte) and remodeling (mammary gland involution), and paradoxically participate in tumor initiation and progression. Expression of miR-424(322)/-503 is governed by unique mechanisms involving sex hormones. Here, we summarize current literature and provide a primer for future endeavors.