Is Runx a linchpin for developmental signaling in metazoans?

RUNX1 promotes proliferation and migration in non-small cell lung cancer cell lines via the mTOR pathway

RUNX1, a member of the RUNX family of metazoan transcription factors, participates in the regulation of differentiation, proliferation, and other processes involved in growth and development. It also functions in the occurrence and development of tumors. However, the role and mechanism of action of RUNX1 in non-small cell lung cancer (NSCLC) are not yet clear. We used a bioinformatics approach as well as in vitro and in vivo assays to evaluate the role of RUNX1 in NSCLC as the molecular mechanisms underlying its effects. Using the TCGA, GEO, GEPIA (Gene Expression Profiling Interactive Analysis), and Kaplan-Meier databases, we screened the differentially expressed genes (DEGs) and found that RUNX1 was highly expressed in lung cancer and was associated with a poor prognosis. Immunohistochemical staining based on tissue chips from 110 samples showed that the expression of RUNX1 in lung cancer tissues was higher than that in adjacent normal tissues and was positively correlated with lymph node metastasis and TNM staging. In vitro experiments, we found that RUNX1 overexpression promoted cell proliferation and migration functions and affected downstream functional proteins by regulating the activity of the mTOR pathway, as confirmed by an analysis using the mTOR pathway inhibitor rapamycin. In addition, RUNX1 affected PD-L1 expression via the mTOR pathway. These results indicate that RUNX1 is a potential therapeutic target for NSCLC.

The Brain’s Microvascular Response to High Glycemia and to the Inhibition of Soluble Epoxide Hydrolase Is Sexually Dimorphic

Biological sex and a high glycemic diet (HGD) contribute to dementia, yet little is known about the operative molecular mechanisms. Our goal was to understand the differences between males and females in the multi-genomic response of the hippocampal microvasculature to the HGD, and whether there was vasculoprotection via the inhibition of soluble epoxide hydrolase (sEHI). Adult wild type mice fed high or low glycemic diets for 12 weeks, with or without an sEHI inhibitor (t-AUCB), had hippocampal microvessels isolated by laser-capture microdissection. Differential gene expression was determined by microarray and integrated multi-omic bioinformatic analyses. The HGD induced opposite effects in males and females: the HGD-upregulated genes were involved in neurodegeneration or neuroinflammation in males, whereas in females they downregulated the same pathways, favoring neuroprotection. In males, the HGD was associated with a greater number of clinical diseases than in females, the sEHI downregulated genes involved in neurodegenerative diseases to a greater extent with the HGD and compared to females. In females, the sEHI downregulated genes involved in endothelial cell functions to a greater extent with the LGD and compared to males. Our work has potentially important implications for sex-specific therapeutic targets for vascular dementia and cardiovascular diseases in males and females.

Molecular basis of ocean acidification sensitivity and adaptation in Mytilus galloprovincialis

Predicting the potential for species adaption to climate change is challenged by the need to identify the physiological mechanisms that underpin species vulnerability. Here, we investigated the sensitivity to ocean acidification in marine mussels during early development, and specifically the trochophore stage. Using RNA and DNA sequencing and in situ RNA hybridization, we identified developmental processes associated with abnormal development and rapid adaptation to low pH. Trochophores exposed to low pH seawater exhibited 43 differentially expressed genes. Gene annotation and in situ hybridization of differentially expressed genes point to pH sensitivity of (1) shell field development and (2) cellular stress response. Five genes within these two processes exhibited shifts in allele frequencies indicative of a potential for rapid adaptation. This case study contributes direct evidence that protecting species’ existing genetic diversity is a critical management action to facilitate species resilience to climate change.

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Marine mussel larval development and genetic adaptation in low pH seawater

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RNA and DNA responses reveal impacts on shell field development and cell stress

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Five genes exhibited both physiological sensitivity and long-term adaptive potential

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Conserving standing genetic variation could bolster resilience to global change

Unique N-terminal sequences in two Runx1 isoforms are dispensable for Runx1 function

Background

The Runt-related transcription factors (Runx) are a family of evolutionarily conserved transcriptional regulators that play multiple roles in the developmental control of various cell types. Among the three mammalian Runx proteins, Runx1 is essential for definitive hematopoiesis and its dysfunction leads to human leukemogenesis. There are two promoters, distal (P1) and proximal (P2), in the Runx1 gene, which produce two Runx1 isoforms with distinct N-terminal amino acid sequences, P1-Runx1 and P2-Runx1. However, it remains unclear whether P2-Runx specific N-terminal sequence have any specific function for Runx1 protein.

Results

To address the function of the P2-Runx1 isoform, we established novel mutant mouse models in which the translational initiation AUG (+1) codon for P2-Runx1 isoform was modulated. We found that a truncated P2-Runx1 isoform is translated from a downstream non-canonical AUG codon. Importantly, the truncated P2-Runx1 isoform is sufficient to support primary hematopoiesis, even in the absence of the P1-Runx1 isoform. Furthermore, the truncated P2-Runx1 isoform was able to restore defect in basophil development caused by loss of the P1-Runx1 isoform. The truncated P2-Runx1 isoform was more stable than the canonical P2-Runx1 isoform.

Conclusions

Our results demonstrate that the N-terminal sequences specific for P2-Runx1 are dispensable for Runx1 function, and likely serve as a de-stabilization module to regulate Runx1 production.

Electronic supplementary material

The online version of this article (10.1186/s12861-017-0156-y) contains supplementary material, which is available to authorized users.

LRG1 promotes proliferation and inhibits apoptosis in colorectal cancer cells via RUNX1 activation

Leucine-rich-alpha-2-glycoprotein 1 (LRG1) has been shown to be involved in various human malignancies. Whether it plays a role in colorectal cancer (CRC) development remains unclear. Here, we investigated whether and through what mechanism LRG1 functions in human CRC cells. The plasma level of LRG1 was significantly increased in CRC patients, but it was remarkably decreased in patients with resected colorectal cancers. Meanwhile, both mRNA and protein levels of LRG1 were remarkable overexpressed in CRC tissues than normal tissues. The knockdown of LRG1 significantly inhibited cell proliferation, induced cell cycle arrest at the G0/G1 phase, and promoted apoptosis in SW480 and HCT116 cells in vitro. In addition, LRG1 silencing led to the downregulation of the levels of key cell cycle factors, such as cyclin D1, B, and E and anti-apoptotic B-cell lymphoma-2(Bcl-2). However, it up-regulated the expression of pro-apoptotic Bax and cleaved caspase-3. Furthermore, RUNX1 could be induced by LRG1 in a concentration-dependent manner, while the knockdown of RUNX1 blocked the promotion of the proliferation and inhibition of apoptosis induced by LRG1. Collectively, these findings indicate that LRG1 plays a crucial role in the proliferation and apoptosis of CRC by regulating RUNX1 expression. Thus, LRG1 may be a potential detection biomarker as well as a marker for monitoring recurrence and therapeutic target for CRC.

RUNX in Invertebrates

Runx genes have been identified in all metazoans and considerable conservation of function observed across a wide range of phyla. Thus, insight gained from studying simple model organisms is invaluable in understanding RUNX biology in higher animals. Consequently, this chapter will focus on the Runx genes in the diploblasts, which includes sea anemones and sponges, as well as the lower triploblasts, including the sea urchin, nematode, planaria and insect. Due to the high degree of functional redundancy amongst vertebrate Runx genes, simpler model organisms with a solo Runx gene, like C. elegans, are invaluable systems in which to probe the molecular basis of RUNX function within a whole organism. Additionally, comparative analyses of Runx sequence and function allows for the development of novel evolutionary insights. Strikingly, recent data has emerged that reveals the presence of a Runx gene in a protist, demonstrating even more widespread occurrence of Runx genes than was previously thought. This review will summarize recent progress in using invertebrate organisms to investigate RUNX function during development and regeneration, highlighting emerging unifying themes.

An Elk transcription factor is required for Runx-dependent survival signaling in the sea urchin embryo

Elk proteins are Ets family transcription factors that regulate cell proliferation, survival, and differentiation in response to ERK (extracellular-signal regulated kinase)-mediated phosphorylation. Here we report the embryonic expression and function of Sp-Elk, the single Elk gene of the sea urchin Strongylocentrotus purpuratus. Sp-Elk is zygotically expressed throughout the embryo beginning at late cleavage stage, with peak expression occurring at blastula stage. Morpholino antisense-mediated knockdown of Sp-Elk causes blastula-stage developmental arrest and embryo disintegration due to apoptosis, a phenotype that is rescued by wild-type Elk mRNA. Development is also rescued by Elk mRNA encoding a serine to aspartic acid substitution (S402D) that mimics ERK-mediated phosphorylation of a conserved site that enhances DNA binding, but not by Elk mRNA encoding an alanine substitution at the same site (S402A). This demonstrates both that the apoptotic phenotype of the morphants is specifically caused by Elk depletion, and that phosphorylation of serine 402 of Sp-Elk is critical for its anti-apoptotic function. Knockdown of Sp-Elk results in under-expression of several regulatory genes involved in cell fate specification, cell cycle control, and survival signaling, including the transcriptional regulator Sp-Runt-1 and its target Sp-PKC1, both of which were shown previously to be required for cell survival during embryogenesis. Both Sp-Runt-1 and Sp-PKC1 have sequences upstream of their transcription start sites that specifically bind Sp-Elk. These results indicate that Sp-Elk is the signal-dependent activator of a feed-forward gene regulatory circuit, consisting also of Sp-Runt-1 and Sp-PKC1, which actively suppresses apoptosis in the early embryo.

Runx2 contributes to the regenerative potential of the mammary epithelium

Although best known for its role in bone development and associated structures the transcription factor RUNX2 is expressed in a wide range of lineages, including those of the mammary gland. Previous studies have indicated that Runx2 can regulate aspects of mammary cell function and influence the properties of cancer cells. In this study we investigate the role of Runx2 in the mammary stem/progenitor population and its relationship with WNT signalling. Results show that RUNX2 protein is differentially expressed throughout embryonic and adult development of the murine mammary gland with high levels of expression in mammary stem-cell enriched cultures. Importantly, functional analysis reveals a role for Runx2 in mammary stem/progenitor cell function in in vitro and in vivo regenerative assays. Furthermore, RUNX2 appears to be associated with WNT signalling in the mammary epithelium and is specifically upregulated in mouse models of WNT-driven breast cancer. Overall our studies reveal a novel function for Runx2 in regulating mammary epithelial cell regenerative potential, possibly acting as a downstream target of WNT signalling.

Heterogeneous generation of new cells in the adult echinoderm nervous system

Adult neurogenesis, generation of new functional cells in the mature central nervous system (CNS), has been documented in a number of diverse organisms, ranging from humans to invertebrates. However, the origin and evolution of this phenomenon is still poorly understood for many of the key phylogenetic groups. Echinoderms are one such phylum, positioned as a sister group to chordates within the monophyletic clade Deuterostomia. They are well known for the ability of their adult organs, including the CNS, to completely regenerate after injury. Nothing is known, however, about production of new cells in the nervous tissue under normal physiological conditions in these animals. In this study, we show that new cells are continuously generated in the mature radial nerve cord (RNC) of the sea cucumber Holothuria glaberrima. Importantly, this neurogenic activity is not evenly distributed, but is significantly more extensive in the lateral regions of the RNC than along the midline. Some of the new cells generated in the apical region of the ectoneural neuroepithelium leave their place of origin and migrate basally to populate the neural parenchyma. Gene expression analysis showed that generation of new cells in the adult sea cucumber CNS is associated with transcriptional activity of genes known to be involved in regulation of various aspects of neurogenesis in other animals. Further analysis of one of those genes, the transcription factor Myc, showed that it is expressed, in some, but not all radial glial cells, suggesting heterogeneity of this CNS progenitor cell population in echinoderms.

The RUNX family: developmental regulators in cancer

RUNX proteins belong to a family of metazoan transcription factors that serve as master regulators of development. They are frequently deregulated in human cancers, indicating a prominent and, at times, paradoxical role in cancer pathogenesis. The contextual cues that direct RUNX function represent a fast-growing field in cancer research and could provide insights that are applicable to early cancer detection and treatment. This Review describes how RUNX proteins communicate with key signalling pathways during the multistep progression to malignancy; in particular, we highlight the emerging partnership of RUNX with p53 in cancer suppression.

RUNX2 in mammary gland development and breast cancer

Runx2 is best known as an essential factor in osteoblast differentiation and bone development but, like many other transcription factors involved in development, is known to operate over a much wider tissue range. Our understanding of these other aspects of Runx2 function is still at a relatively early stage and the importance of its role in cell fate decisions and lineage maintenance in non-osseous tissues is only beginning to emerge. One such tissue is the mammary gland, where Runx2 is known to be expressed and participate in the regulation of mammary specific genes. Furthermore, differential and temporal expression of this gene is observed during mammary epithelial differentiation in vivo, strongly indicative of an important functional role. Although the precise nature of that role remains elusive, preliminary evidence hints at possible involvement in the regulation of mammary stem and/or progenitor cells. As with many genes important in regulating cell fate, RUNX2 has also been linked to metastatic cancer where in some established breast cell lines, retention of expression is associated with a more invasive phenotype. More recently, expression analysis has been extended to primary breast cancers where high levels of RUNX2 align with a specific subtype of the disease. That RUNX2 expression correlates with the so called "Triple Negative" subtype is particularly interesting given the known cross talk between Runx2 and estrogen receptor signaling pathways. This review summaries our current understanding of Runx2 in mammary gland development and cancer, and postulates a role that may link both these processes.

Sea urchin akt activity is Runx-dependent and required for post-cleavage stage cell division

In animal development following the initial cleavage stage of embryogenesis, the cell cycle becomes dependent on intercellular signaling and controlled by the genomically encoded ontogenetic program. Runx transcription factors are critical regulators of metazoan developmental signaling, and we have shown that the sea urchin Runx gene runt-1, which is globally expressed during early embryogenesis, functions in support of blastula stage cell proliferation and expression of the mitogenic genes pkc1, cyclinD, and several wnts. To obtain a more comprehensive list of early runt-1 regulatory targets, we screened a Strongylocentrotus purpuratus microarray to identify genes mis-expressed in mid-blastula stage runt-1 morphants. This analysis showed that loss of Runx function perturbs the expression of multiple genes involved in cell division, including the pro-growth and survival kinase Akt (PKB), which is significantly underexpressed in runt-1 morphants. Further genomic analysis revealed that Akt is encoded by two genes in the S. purpuratus genome, akt-1 and akt-2, both of which contain numerous canonical Runx target sequences. The transcripts of both genes accumulate several fold during blastula stage, contingent on runt-1 expression. Inhibiting Akt expression or activity causes blastula stage cell cycle arrest, whereas overexpression of akt-1 mRNA rescues cell proliferation in runt-1 morphants. These results indicate that post-cleavage stage cell division requires Runx-dependent expression of akt.

Myeloid leukemia factor is a conserved regulator of RUNX transcription factor activity involved in hematopoiesis

Defining the function of the genes that, like RUNX1, are deregulated in blood cell malignancies represents an important challenge. Myeloid leukemia factors (MLFs) constitute a poorly characterized family of conserved proteins whose founding member, MLF1, has been associated with acute myeloid leukemia in humans. To gain insight into the functions of this family, we investigated the role of the Drosophila MLF homolog during blood cell development. Here we report that mlf controls the homeostasis of the Drosophila hematopoietic system. Notably, mlf participates in a positive feedback loop to fine tune the activity of the RUNX transcription factor Lozenge (LZ) during development of the crystal cells, one of the two main blood cell lineages in Drosophila. At the molecular level, our data in cell cultures and in vivo strongly suggest that MLF controls the number of crystal cells by protecting LZ from degradation. Remarkably, it appears that the human MLF1 protein can substitute for MLF in the crystal cell lineage. In addition, MLF stabilizes the human oncogenic fusion protein RUNX1-ETO and is required for RUNX1-ETO-induced blood cell disorders in a Drosophila model of leukemia. Finally, using the human leukemic blood cell line Kasumi-1, we show that MLF1 depletion impairs RUNX1-ETO accumulation and reduces RUNX1-ETO-dependent proliferation. Thus, we propose that the regulation of RUNX protein levels is a conserved feature of MLF family members that could be critical for normal and pathological blood cell development.

Runx1 is a tumor suppressor gene in the mouse gastrointestinal tract

The Runx1 transcription factor plays an important role in tissue homeostasis through its effects on stem/progenitor cell populations and differentiation. The effect of Runx1 on epithelial differentiation of the secretory cell lineage of the colon was recently demonstrated. This study aimed to examine the role of Runx1 in tumor development in epithelial cells of the gastrointestinal tract. Conditional knockout mice that lacked Runx1 expression in epithelial cells of the GI tract were generated. These mice were crossed onto the Apc(Min) background, killed and their intestinal tumor phenotypes were compared with Apc(Min) Runx1 wild-type control mice. Apc-wild-type Runx1-mutant mice were also examined for tumor development. Colons from Runx1 knockout and wild-type mice were used for genome-wide mRNA expression analyses followed by gene-specific quantitative RT-PCR of whole colon and colon epithelium to identify Runx1 target genes. Runx1 deficiency in intestinal epithelial cells significantly enhanced tumorigenesis in Apc(Min) mice. Notably, epithelial Runx1 deficiency in Apc-wild-type mice was sufficient to cause tumor development. Absence of Runx1 was associated with global changes in the expression of genes involved in inflammation and intestinal metabolism, and with gene sets indicative of a metastatic phenotype and poor prognosis. Gene-specific analysis of Runx1-deficient colon epithelium revealed increased expression of genes linked to an expansion of the stem/progenitor cell population. These results identify Runx1 as a novel tumor suppressor gene for gastrointestinal tumors and support a role for Runx1 in maintaining the balance between the intestinal stem/progenitor cell population and epithelial differentiation of the GI tract.

ODAM Expression Inhibits Human Breast Cancer Tumorigenesis

We have posited that Odontogenic Ameloblast Associated Protein (ODAM) serves as a novel prognostic biomarker in breast cancer and now have investigated its potential role in regulating tumor growth and metastasis. Human breast cancer MDA-MB-231 cells were transfected with a recombinant ODAM plasmid construct (or, as a control, the plasmid vector alone). ODAM expression increased adhesion and apoptosis of the transfected MDA-MB-231 cells and suppressed their growth rate, migratory activity, and capability to invade extracellular matrix-coated membranes. Implantation of such cells into mouse mammary fat pads resulted in significantly smaller tumors than occurred in animals that received control cells; furthermore, ODAM-expressing cells, when injected intravenously into mice, failed to metastasize, whereas the control-transfected counterparts produced extensive lung lesions. Our finding that induction of ODAM expression in human breast cancer cells markedly inhibited their neoplastic properties provides further evidence for the regulatory role of this molecule in tumorigenesis and, consequently, is of potential clinical import.

The Runx transcriptional co-activator, CBFbeta, is essential for invasion of breast cancer cells

Background

The transcription factor Runx2 has an established role in cancers that metastasize to bone. In metastatic breast cancer cells Runx2 is overexpressed and contributes to the invasive capacity of the cells by regulating the expression of several invasion genes. CBFβ is a transcriptional co-activator that is recruited to promoters by Runx transcription factors and there is considerable evidence that CBFβ is essential for the function of Runx factors. However, overexpression of Runx1 can partially rescue the lethal phenotype in CBFβ-deficient mice, indicating that increased levels of Runx factors can, in some situations, overcome the requirement for CBFβ. Since Runx2 is overexpressed in metastatic breast cancer cells, and there are no reports of CBFβ expression in breast cells, we sought to determine whether Runx2 function in these cells was dependent on CBFβ. Such an interaction might represent a viable target for therapeutic intervention to inhibit bone metastasis.

Results

We show that CBFβ is expressed in the metastatic breast cancer cells, MDA-MB-231, and that it associates with Runx2. Matrigel invasion assays and RNA interference were used to demonstrate that CBFβ contributes to the invasive capacity of these cells. Subsequent analysis of Runx2 target genes in MDA-MB-231 cells revealed that CBFβ is essential for the expression of Osteopontin, Matrixmetalloproteinase-13, Matrixmetalloproteinase-9, and Osteocalcin but not for Galectin-3. Chromatin immunoprecipitation analysis showed that CBFβ is recruited to both the Osteopontin and the Galectin-3 promoters.

Conclusions

CBFβ is expressed in metastatic breast cancer cells and is essential for cell invasion. CBFβ is required for expression of several Runx2-target genes known to be involved in cell invasion. However, whilst CBFβ is essential for invasion, not all Runx2-target genes require CBFβ. We conclude that CBFβ is required for a subset of Runx2-target genes that are sufficient to maintain the invasive phenotype of the cells. These findings suggest that the interaction between Runx2 and CBFβ might represent a viable target for therapeutic intervention to inhibit bone metastasis.

A genome-wide RNA interference screen identifies a differential role of the mediator CDK8 module subunits for GATA/ RUNX-activated transcription in Drosophila

Transcription factors of the RUNX and GATA families play key roles in the control of cell fate choice and differentiation, notably in the hematopoietic system. During Drosophila hematopoiesis, the RUNX factor Lozenge and the GATA factor Serpent cooperate to induce crystal cell differentiation. We used Serpent/Lozenge-activated transcription as a paradigm to identify modulators of GATA/RUNX activity by a genome-wide RNA interference screen in cultured Drosophila blood cells. Among the 129 factors identified, several belong to the Mediator complex. Mediator is organized in three modules plus a regulatory "CDK8 module," composed of Med12, Med13, CycC, and Cdk8, which has long been thought to behave as a single functional entity. Interestingly, our data demonstrate that Med12 and Med13 but not CycC or Cdk8 are essential for Serpent/Lozenge-induced transactivation in cell culture. Furthermore, our in vivo analysis of crystal cell development show that, while the four CDK8 module subunits control the emergence and the proliferation of this lineage, only Med12 and Med13 regulate its differentiation. We thus propose that Med12/Med13 acts as a coactivator for Serpent/Lozenge during crystal cell differentiation independently of CycC/Cdk8. More generally, we suggest that the set of conserved factors identified herein may regulate GATA/RUNX activity in mammals.

Runx transcription factors: lineage-specific regulators of neuronal precursor cell proliferation and post-mitotic neuron subtype development

Runt-related (RUNX) genes encode evolutionarily conserved transcription factors that play essential roles during development and adult tissue homeostasis. RUNX proteins regulate the transition from proliferation to differentiation in a variety of cell lineages. Moreover, they control the diversification of distinct cellular phenotypes in numerous tissues. Alterations of RUNX functions are associated with several cancers and other human pathologies, underscoring the vital roles of these transcription factors in adult organs. Insights into the functions and regulations of mammalian RUNX proteins have been provided mostly by studies of RUNX involvement in mechanisms of hematopoietic and skeletal development and disease. A growing number of recent investigations are revealing new functions for RUNX family members during the development of the mammalian nervous system. This review will discuss recent progress in the study of RUNX protein involvement in mammalian neural development, with emphasis on the differentiation of olfactory, sensory, and motor neuron lineages.

The evolution of Runx genes II. The C-terminal Groucho recruitment motif is present in both eumetazoans and homoscleromorphs but absent in a haplosclerid demosponge

Background

The Runt DNA binding domain (Runx) defines a metazoan family of sequence-specific transcription factors with essential roles in animal ontogeny and stem cell based development. Depending on cis-regulatory context, Runx proteins mediate either transcriptional activation or repression. In many contexts Runx-mediated repression is carried out by Groucho/TLE, recruited to the transcriptional complex via a C-terminal WRPY sequence motif that is found encoded in all heretofore known Runx genes.

Findings

Full-length Runx genes were identified in the recently sequenced genomes of phylogenetically diverse metazoans, including placozoans and sponges, the most basally branching members of that clade. No sequences with significant similarity to the Runt domain were found in the genome of the choanoflagellate Monosiga brevicollis, confirming that Runx is a metazoan apomorphy. A contig assembled from genomic sequences of the haplosclerid demosponge Amphimedon queenslandica was used to construct a model of the single Runx gene from that species, AmqRunx, the veracity of which was confirmed by expressed sequences. The encoded sequence of the Runx protein OscRunx from the homoscleromorph sponge Oscarella carmella was also obtained from assembled ESTs. Remarkably, a syntenic linkage between Runx and Supt3h, previously reported in vertebrates, is conserved in A. queenslandica. Whereas OscRunx encodes a C-terminal Groucho-recruitment motif, AmqRunx does not, although a Groucho homologue is found in the A. queenslandica genome.

Conclusion

Our results are consistent with the hypothesis that sponges are paraphyletic, and suggest that Runx-WRPY mediated recruitment of Groucho to cis-regulatory sequences originated in the ancestors of eumetazoans following their divergence from demosponges.