IntroductionPluripotent stem cells are increasingly used to build therapeutic models, including the transplantation of neural progenitors derived from human embryonic stem cells (hESCs). Recently, long non-coding RNAs (lncRNAs), including delta-like homolog 1 gene and the type III iodothyronine deiodinase gene (DLK1-DIO3) imprinted locus-derived maternally expressed gene 3 (MEG3), were found to be expressed during neural development. The deregulation of these lncRNAs is associated with various neurological diseases. The imprinted locus DLK1-DIO3 encodes abundant non-coding RNAs (ncRNAs) that are regulated by differential methylation of the locus. We aim to study the correlation between the DLK1-DIO3-derived ncRNAs and the capacity of hESCs to differentiate into neural lineages.MethodsWe classified hESC sublines into MEG3-ON and MEG3-OFF based on the expression levels of MEG3 and its downstream microRNAs as detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). A cDNA microarray was used to analyze the gene expression profiles of hESCs. To investigate the capacity of neural differentiation in MEG3-ON and MEG3-OFF hESCs, we performed neural lineage differentiation followed by neural lineage marker expression and neurite formation analyses via qRT-PCR and immunocytochemistry, respectively. MEG3-knockdown via small interfering RNA (siRNA) and small hairpin RNA (shRNA) was used to investigate the potential causative effect of MEG3 in regulating neural lineage-related gene expression.ResultsDLK1-DIO3-derived ncRNAs were repressed in MEG3-OFF hESCs compared with those in the MEG3-ON hESCs. The transcriptome profile indicated that many genes related to nervous system development and neural-type tumors were differentially expressed in MEG3-OFF hESCs. Three independent MEG3-knockdown assays using different siRNA and shRNA constructs consistently resulted in downregulation of some neural lineage genes. Lower expression levels of stage-specific neural lineage markers and reduced neurite formation were observed in neural lineage-like cells derived from MEG3-OFF-associated hESCs compared with those in the MEG3-ON groups at the same time points after differentiation.ConclusionsRepression of ncRNAs derived from the DLK1-DIO3 imprinted locus is associated with reduced neural lineage differentiation potential in hESCs.Electronic supplementary materialThe online version of this article (doi:10.1186/scrt535) contains supplementary material, which is available to authorized users.

Activity of the Axl receptor tyrosine kinase is positively correlated with tumor metastasis; however, its detailed role in the mechanism of tumor invasion is still not completely understood. Here, we show that Axl enhances the expression of matrix metalloproteinase 9 (MMP-9), required for Axl-mediated invasion both in vitro and in vivo. We found that the highly selective MEK1/2 inhibitors U0126 and PD98059, and the expressed dominant-negative form of extracellular signal-regulated kinase (ERK), completely block Axl-mediated MMP-9 activation. In contrast, the phosphatidylinositol 3-kinase inhibitor LY294002 and wortmannin had little effect on activation. Interestingly, however, the Axl ligand Gas6 is not involved in Axl-mediated MMP-9 activation. Mutation of Glu59Axl and Thr77 Axl dramatically reduced Gas6-Axl binding but continued to induce MMP-9 activation. In addition, overexpression of Axl-activated ERK and enhanced nuclear factor-jB (NF-jB) transactivation and brahma-related gene-1 (Brg-1) translocation. Exposure to the NF-jB inhibitor silibinin, which inhibits IjBa kinase activity, or overexpression of the dominant-negative mutant IjB and Brg-1 strikingly inhibited Axl-mediated MMP-9 activation. These data indicate that coordination of ERK signaling and NF-jB and Brg-1 activation are indispensable to regulation of Axl-dependent MMP-9 gene transcription. Together with previous data, our results provide a plausible mechanism for Axl-mediated tumor invasion and establish a functional link between the Axl and MMP-9 signaling pathways.

Stem cell activity is subject to non-cell-autonomous regulation from the local microenvironment, or niche. In adaption to varying physiological conditions and the ever-changing external environment, the stem cell niche has evolved with multifunctionality that enables stem cells to detect these changes and to communicate with remote cells/tissues to tailor their activity for organismal needs. The cyclic growth of hair follicles is powered by hair follicle stem cells (HFSCs). Using HFSCs as a model, we categorize niche cells into 3 functional modules, including signaling, sensing and message-relaying. Signaling modules, such as dermal papilla cells, immune cells and adipocytes, regulate HFSC activity through short-range cell-cell contact or paracrine effects. Macrophages capacitate the HFSC niche to sense tissue injury and mechanical cues and adipocytes seem to modulate HFSC activity in response to systemic nutritional states. Sympathetic nerves implement the message-relaying function by transmitting external light signals through an ipRGC-SCN-sympathetic circuit to facilitate hair regeneration. Hair growth can be disrupted by niche pathology, e.g. dysfunction of dermal papilla cells in androgenetic alopecia and influx of auto-reacting T cells in alopecia areata and lichen planopilaris. Understanding the functions and pathological changes of the HFSC niche can provide new insight for the treatment of hair loss.