SOX-11 regulates LINE-1 retrotransposon activity during neuronal differentiation

Effects of transcription factor SOX11 on the biological behavior of neuroblastoma cell and potential regulatory mechanism

Purpose

This study aimed to analyze the expression and prognosis of SRY-box transcription factor 11 (SOX11) in neuroblastoma (NB), as well as the biological function and potential regulatory mechanism of SOX11 in NB.

Methods

Public RNA sequencing was used to detect the expression level of SOX11. The Kaplan-Meier curve and hazard ratios (HR) were used to determine the prognostic value of SOX11 in NB. Functional analyses were performed using CCK8, wound healing assay, and transwell invasion assay. Finally, the potential target genes of SOX11 were predicted by Harmonizonme (Ma'ayan Laboratory) and Cistrome Data Browser (Cistrome Project) database to explore the potential molecular mechanism of SOX11 in NB.

Results

Compared with normal adrenal tissue, the expression of SOX11 in NB tissue was significantly upregulated. The Kaplan-Meier curve showed that high expression of SOX11 was associated with poor prognosis in children with NB (HR, 1.719; P = 0.049). SOX11 knockdown suppressed the migration capacity of SK-N-SH cells but did not affect proliferation and invasion capacity. Enhancer of zeste homolog 2 (EZH2) may be a potential downstream target gene for the transcription factor SOX11 to play a role in NB.

Conclusion

The transcription factor SOX11 was significantly upregulated in NB. SOX11 knockdown suppressed the migration capacity of NB cell SK-N-SH. SOX11 may promote the progression of NB by targeting EZH2.

Transposon control as a checkpoint for tissue regeneration

Tissue regeneration requires precise temporal control of cellular processes such as inflammatory signaling, chromatin remodeling and proliferation. The combination of these processes forms a unique microenvironment permissive to the expression, and potential mobilization of, transposable elements (TEs). Here, we develop the hypothesis that TE activation creates a barrier to tissue repair that must be overcome to achieve successful regeneration. We discuss how uncontrolled TE activity may impede tissue restoration and review mechanisms by which TE activity may be controlled during regeneration. We posit that the diversification and co-evolution of TEs and host control mechanisms may contribute to the wide variation in regenerative competency across tissues and species.

Deep analysis of neuroblastoma core regulatory circuitries using online databases and integrated bioinformatics shows their pan-cancer roles as prognostic predictors

AIM

Neuroblastoma is a heterogeneous childhood cancer derived from the neural crest. The dual cell identities of neuroblastoma include Mesenchymal (MES) and Adrenergic (ADRN). These identities are conferred by a small set of tightly-regulated transcription factors (TFs) binding super enhancers, collectively forming core regulatory circuitries (CRCs). The purpose of this study was to gain a deep understanding of the role of MES and ADRN TFs in neuroblastoma and other cancers as potential indicators of disease prognosis, progression, and relapse.

METHODS

To that end, we first investigated the expression and mutational profile of MES and ADRN TFs in neuroblastoma. Moreover, we established their correlation with neuroblastoma risk groups and overall survival while establishing their extended networks with long non-coding RNAs (lncRNAs). Furthermore, we analysed the pan-cancer expression and mutational profile of these TFs and their correlation with patient survival and finally their network connectivity, using a panel of bioinformatic tools including GEPIA2, human pathology atlas, TIMER2, Omicsnet, and Cytoscape.

RESULTS

We show the association of multiple MES and ADRN TFs with neuroblastoma risk groups and overall survival and find significantly higher expression of various MES and ADRN TFs compared to normal tissues and their association with overall survival and disease-free survival in multiple cancers. Moreover, we report the strong correlation of the expression of these TFs with the infiltration of stromal and immune cells in the tumour microenvironment and with stemness and metastasis-related genes. Furthermore, we reveal extended pan-cancer networks comprising these TFs that influence the tumour microenvironment and metastasis and may be useful indicators of cancer prognosis and patient survival.

CONCLUSION

Our meta-analysis shows the significance of MES and ADRN TFs as indicators of patient prognosis and the putative utility of these TFs as potential novel biomarkers.

Factors Regulating the Activity of LINE1 Retrotransposons

LINE-1 (L1) is a class of autonomous mobile genetic elements that form somatic mosaicisms in various tissues of the organism. The activity of L1 retrotransposons is strictly controlled by many factors in somatic and germ cells at all stages of ontogenesis. Alteration of L1 activity was noted in a number of diseases: in neuropsychiatric and autoimmune diseases, as well as in various forms of cancer. Altered activity of L1 retrotransposons for some pathologies is associated with epigenetic changes and defects in the genes involved in their repression. This review discusses the molecular genetic mechanisms of the retrotransposition and regulation of the activity of L1 elements. The contribution of various factors controlling the expression and distribution of L1 elements in the genome occurs at all stages of the retrotransposition. The regulation of L1 elements at the transcriptional, post-transcriptional and integration into the genome stages is described in detail. Finally, this review also focuses on the evolutionary aspects of L1 accumulation and their interplay with the host regulation system.

TFs for TEs: the transcription factor repertoire of mammalian transposable elements

In this review, Hermant and Torres-Padilla summarize and discuss the transcription factors known to be involved in the sequence-specific recognition and transcriptional activation of specific transposable element families or subfamilies.

Transposable elements (TEs) are genetic elements capable of changing position within the genome. Although their mobilization can constitute a threat to genome integrity, nearly half of modern mammalian genomes are composed of remnants of TE insertions. The first critical step for a successful transposition cycle is the generation of a full-length transcript. TEs have evolved cis-regulatory elements enabling them to recruit host-encoded factors driving their own, selfish transcription. TEs are generally transcriptionally silenced in somatic cells, and the mechanisms underlying their repression have been extensively studied. However, during germline formation, preimplantation development, and tumorigenesis, specific TE families are highly expressed. Understanding the molecular players at stake in these contexts is of utmost importance to establish the mechanisms regulating TEs, as well as the importance of their transcription to the biology of the host. Here, we review the transcription factors known to be involved in the sequence-specific recognition and transcriptional activation of specific TE families or subfamilies. We discuss the diversity of TE regulatory elements within mammalian genomes and highlight the importance of TE mobilization in the dispersal of transcription factor-binding sites over the course of evolution.

SOX11, SOX10 and MITF Gene Interaction: A Possible Diagnostic Tool in Malignant Melanoma

Malignant melanoma (MM) is a highly heterogenic tumor whose histological diagnosis might be difficult. This study aimed to investigate the diagnostic and prognostic utility of the conventional pan-melanoma cocktail members (HMB-45, melan-A and tyrosinase), in conjunction with SOX10 and SOX11 immunohistochemical (IHC) expression. In 105 consecutive cases of MMs and 44 of naevi, the IHC examination was performed using the five-abovementioned markers, along with microphthalmia transcription factor (MITF), S100, and Ki67. Correlation with the clinicopathological factors and a long-term follow-up was also done. Survival analysis was performed with Kaplan–Meier curves and compared with TCGA public datasets. None of the 44 naevi expressed SOX11, but its positivity was seen in 52 MMs (49.52%), being directly correlated with lymphovascular invasion, the Ki67 index, and SOX10 expression. HMB-45, SOX10, and tyrosinase, but not melan-A, proved to differentiate the naevi from MMs successfully, with high specificity. Triple MITF/SOX10/SOX11 co-expression was seen in 9 out of 15 negative conventional pan-melanoma-cocktail cases. The independent prognostic value was proved for the conventional pan-melanoma cocktail (triple positivity for HMB-45, melan-A, and tyrosinase) and, independently for HMB-45 and tyrosinase, but not for melan-A, SOX10, or SOX11. As consequence, to differentiate MMs from benign naevi, melan-A should be substituted by SOX10 in the conventional cocktail. Although the conventional pan-melanoma cocktail, along with S100 can be used for the identification of melanocytic origin of tumor cells and predicting prognosis of MMs, the conventional-adapted cocktail (triple positivity for HMB-45, SOX10, and tyrosinase) has a slightly higher diagnostic specificity. SOX11 can be added to identify the aggressive MMs with risk for lymphatic dissemination and the presence of circulating tumor cells.