Fussel-15, a novel Ski/Sno homolog protein, antagonizes BMP signaling

Molecular analyses of zebrafish V0v spinal interneurons and identification of transcriptional regulators downstream of Evx1 and Evx2 in these cells

BACKGROUND

V0v spinal interneurons are highly conserved, glutamatergic, commissural neurons that function in locomotor circuits. We have previously shown that Evx1 and Evx2 are required to specify the neurotransmitter phenotype of these cells. However, we still know very little about the gene regulatory networks that act downstream of these transcription factors in V0v cells.

METHODS

To identify candidate members of V0v gene regulatory networks, we FAC-sorted wild-type and evx1;evx2 double mutant zebrafish V0v spinal interneurons and expression-profiled them using microarrays and single cell RNA-seq. We also used in situ hybridization to compare expression of a subset of candidate genes in evx1;evx2 double mutants and wild-type siblings.

RESULTS

Our data reveal two molecularly distinct subtypes of zebrafish V0v spinal interneurons at 48 h and suggest that, by this stage of development, evx1;evx2 double mutant cells transfate into either inhibitory spinal interneurons, or motoneurons. Our results also identify 25 transcriptional regulator genes that require Evx1/2 for their expression in V0v interneurons, plus a further 11 transcriptional regulator genes that are repressed in V0v interneurons by Evx1/2. Two of the latter genes are hmx2 and hmx3a. Intriguingly, we show that Hmx2/3a, repress dI2 interneuron expression of skor1a and nefma, two genes that require Evx1/2 for their expression in V0v interneurons. This suggests that Evx1/2 might regulate skor1a and nefma expression in V0v interneurons by repressing Hmx2/3a expression.

CONCLUSIONS

This study identifies two molecularly distinct subsets of zebrafish V0v spinal interneurons, as well as multiple transcriptional regulators that are strong candidates for acting downstream of Evx1/2 to specify the essential functional characteristics of these cells. Our data further suggest that in the absence of both Evx1 and Evx2, V0v spinal interneurons initially change their neurotransmitter phenotypes from excitatory to inhibitory and then, later, start to express markers of distinct types of inhibitory spinal interneurons, or motoneurons. Taken together, our findings significantly increase our knowledge of V0v and spinal development and move us closer towards the essential goal of identifying the complete gene regulatory networks that specify this crucial cell type.

Molecular Analyses of V0v Spinal Interneurons and Identification of Transcriptional Regulators Downstream of Evx1 and Evx2 in these Cells

Background

V0v spinal interneurons are highly conserved, glutamatergic, commissural neurons that function in locomotor circuits. We have previously shown that Evx1 and Evx2 are required to specify the neurotransmitter phenotype of these cells. However, we still know very little about the gene regulatory networks that act downstream of these transcription factors in V0v cells.

Methods

To identify candidate members of V0v gene regulatory networks, we FAC-sorted WT and evx1;evx2 double mutant zebrafish V0v spinal interneurons and expression-profiled them using microarrays and single cell RNA-seq. We also used in situ hybridization to compare expression of a subset of candidate genes in evx1;evx2 double mutants and wild-type siblings.

Results

Our data reveal two molecularly distinct subtypes of V0v spinal interneurons at 48 h and suggest that, by this stage of development, evx1;evx2 double mutant cells transfate into either inhibitory spinal interneurons, or motoneurons. Our results also identify 25 transcriptional regulator genes that require Evx1/2 for their expression in V0v interneurons, plus a further 11 transcriptional regulator genes that are repressed in V0v interneurons by Evx1/2. Two of the latter genes are hmx2 and hmx3a. Intriguingly, we show that Hmx2/3a, repress dI2 interneuronal expression of skor1a and nefma, two genes that require Evx1/2 for their expression in V0v interneurons. This suggests that Evx1/2 might regulate skor1a and nefma expression in V0v interneurons by repressing Hmx2/3a expression.

Conclusions

This study identifies two molecularly distinct subsets of V0v spinal interneurons, as well as multiple transcriptional regulators that are strong candidates for acting downstream of Evx1/2 to specify the essential functional characteristics of these cells. Our data further suggest that in the absence of both Evx1 and Evx2, V0v spinal interneurons initially change their neurotransmitter phenotypes from excitatory to inhibitory and then, later, start to express markers of distinct types of inhibitory spinal interneurons, or motoneurons. Taken together, our findings significantly increase our knowledge of V0v and spinal development and move us closer towards the essential goal of identifying the complete gene regulatory networks that specify this crucial cell type.

SKOR1 mediates FER kinase-dependent invasive growth of breast cancer cells

High expression of the non-receptor tyrosine kinase FER is an independent prognostic factor that correlates with poor survival in breast cancer patients. To investigate whether the kinase activity of FER is essential for its oncogenic properties, we developed an ATP analogue-sensitive knock-in allele (FERASKI). Specific FER kinase inhibition in MDA-MB-231 cells reduces migration and invasion, as well as metastasis when xenografted into a mouse model of breast cancer. Using the FERASKI system, we identified Ski family transcriptional corepressor 1 (SKOR1) as a direct FER kinase substrate. SKOR1 loss phenocopies FER inhibition, leading to impaired proliferation, migration and invasion, and inhibition of breast cancer growth and metastasis formation in mice. We show that SKOR1 Y234, a candidate FER phosphorylation site, is essential for FER-dependent tumor progression. Finally, our work suggests that the SKOR1 Y234 residue promotes Smad2/3 signaling through SKOR1 binding to Smad3. Our study thus identifies SKOR1 as a mediator of FER-dependent progression of high-risk breast cancers.

The Drosophila functional Smad suppressing element fuss, a homologue of the human Skor genes, retains pro-oncogenic properties of the Ski/Sno family

Over the years Ski and Sno have been found to be involved in cancer progression e.g. in oesophageal squamous cell carcinoma, melanoma, oestrogen receptor-positive breast carcinoma, colorectal carcinoma, and leukaemia. Often, their prooncogenic features have been linked to their ability of inhibiting the anti-proliferative action of TGF-ß signalling. Recently, not only pro-oncogenic but also anti-oncogenic functions of Ski/Sno proteins have been revealed. Besides Ski and Sno, which are ubiquitously expressed other members of Ski/Sno proteins exist which show highly specific neuronal expression, the SKI Family Transcriptional Corepressors (Skor). Among others Skor1 and Skor2 are involved in the development of Purkinje neurons and a mutation of Skor1 has been found to be associated with restless legs syndrome. But neither Skor1 nor Skor2 have been reported to be involved in cancer progression. Using overexpression studies in the Drosophila eye imaginal disc, we analysed if the Drosophila Skor homologue Fuss has retained the potential to inhibit differentiation and induce increased proliferation. Fuss expressed in cells posterior to the morphogenetic furrow, impairs photoreceptor axon pathfinding and inhibits differentiation of accessory cells. However, if its expression is induced prior to eye differentiation, Fuss might inhibit the differentiating function of Dpp signalling and might maintain proliferative action of Wg signalling, which is reminiscent of the Ski/Sno protein function in cancer.

Inhibition of MAD2B alleviates venous neointimal formation by suppressing VSMCs proliferation and migration

The proliferation and migration of vascular smooth muscle cells (VSMCs) are essential events in venous neointimal hyperplasia (VNH), a culprit of arteriovenous fistula (AVF) malfunction. Mitotic arrest-deficient protein 2B (MAD2B) is a critical regulator of cell proliferation and differentiation in many scenarios. To address the role of MAD2B in VSMCs proliferation and migration during VNH, AVFs from patients with end-stage renal disease (ESRD) and chronic kidney disease (CKD) mice were used to evaluate MAD2B expression. In cultured VSMCs treated with platelet-derived growth factor-BB (PDGF-BB), the effect of MAD2B on VSMCs proliferation and migration was detected by cell counting kit-8 (CCK8) assay, immunofluorescence, wound-healing scratch and transwell assays. Besides, we exploited different small interfering RNAs (siRNAs) to explore the potential mechanisms in the issue. Furthermore, rapamycin was applied to reveal whether MAD2B-associated pathways were involved in its inhibitory effect on VSMCs proliferation and migration. Accordingly, we found that MAD2B expression was enhanced in AVFs from patients with ESRD, CKD mice and VSMCs stimulated by PDGF-BB. Meanwhile, inhibition of MAD2B alleviated VSMCs proliferation and migration while the number of ski-related novel gene (SnoN)-positive VSMCs was also increased in vivo and in vitro. Moreover, gene deletion of MAD2B decreased the level of SnoN protein in PDGF-BB-stimulated VSMCs. Furthermore, rapamycin suppressed the increased expressions of MAD2B and SnoN induced by PDGF-BB. Thus, our study demonstrates that inhibition of MAD2B suppresses the proliferation and migration of VSMCs during VNH via reducing SnoN expression. Moreover, rapamycin exerts an inhibitory effect on intimal hyperplasia, possibly via the MAD2B-SnoN axis.

SKOR1 has a transcriptional regulatory role on genes involved in pathways related to restless legs syndrome

Restless legs syndrome (RLS) is a common sleep-related sensory-motor disorder. It is characterized by uncomfortable sensations in the legs during the evening or at night. The symptoms can be partially relieved by movement, so typically affected individual needs to walk during rest time; this interferes with sleep. GWAS have identified 19 RLS-associated loci. Among the first to be reported and most significant and robustly replicated reports are variants in the SKOR1 noncoding regions. SKOR1 is highly expressed in the CNS of humans and mice. Skor1 acts as a corepressor of Lbx1 transcription factor in mice and these two genes act together to regulate the cell fate of interneurons in the dorsal horn of the spinal cord. Based on this data we investigated the regulatory role of SKOR1 using a global RNA-sequencing approach in human cell lines where SKOR1 was either overexpressed or silenced. For this work we generated and validated a new poly-clonal anti-SKOR1. Pathway and gene set enrichment analyses of the differentially expressed genes showed, among others, enrichment of genes involved in neurodevelopment and iron metabolism, two RLS relevant pathways that were previously found to be enriched in the latest RLS GWAS meta-analysis. Analysis of our different datasets further supports and highlights the regulatory role of SKOR1, which when dysregulated might represent a key pathogenic element of RLS. A better understanding of SKOR1 and its activity could open new avenues of investigation for the development of a much-needed therapy.

Glucocorticoid Enhanced the Expression of Ski in Osteonecrosis of Femoral Head: The Effect on Adipogenesis of Rabbit BMSCs

Glucocorticoid (GC)-induced osteonecrosis has been considered as the most serious side effect in long-term or over-dose steroid therapy. The decreased bone mass and increased marrow fat tissue demonstrated that GC can destroy the normal differentiation of bone marrow mesenchymal stem cells (BMSCs), which accelerates adipogenesis but not osteogenesis. However, the underlying mechanisms are still unclear. Ski, an evolutionary conserved protein, is a multifunctional transcriptional regulator that involved in regulating signaling pathways associated with adipogenesis differentiation, but the concrete function remains unclear. In this work, we first established a methylprednisolone (MPS)-induced osteonecrosis of femoral head (ONFH) rabbit model, in which the expression of Ski, PPAR-γ, and FABP4 was up-regulated compared with control group, and then we induced the isolated BMSCs from rabbit with dexamethasone (Dex) in vitro and the results showed that the Ski expression was up-regulated by Dex in a dose- and time-dependent manner. Therefore, we demonstrated that the expression of Ski was up-regulated in glucocorticoid-related osteonecrosis disease in vivo and in vitro. Moreover, the adipogenesis differentiation capacity of BMSCs was enhanced after induced by Dex, which was identified by Oil Red O staining, and the up-regulated PPAR-γ and FABP4 expression. To further study the function of Ski in BMSC after induced by Dex, Ski specific small interfering RNA (Ski-siRNA) was used. Results showed that knockdown of Ski obviously decreased adipogenesis differentiation evident by Oil Red O staining, and the expression of PPAR-γ and FABP4 was down-regulated simultaneously. Collectively, our findings suggest that Ski increased significantly during glucocorticoid-induced adipogenic differentiation of BMSCs, and the expression level was consistent with adipogenic-related proteins including PPAR-γ and FABP4. Based on the above data, we believe that Ski might become a new molecule in the treatment of GC-induced ONFH and our study could provide a basis for further study on the detailed function of Ski in ONFH.

Biological insights into multiple birth: genetic findings from UK Biobank

The tendency to conceive spontaneous dizygotic (DZ) twins is a complex trait with important contributions from both environmental factors and genetic disposition. In earlier work, we identified the first two genes as maternal susceptibility loci for DZ twinning. The aim of this study was to identify genetic variants influencing multiple births and to genetically correlate the findings across a broad range of traits. We performed a genome-wide association study (GWAS) in 8962 participants with Caucasian ancestry from UK Biobank who reported being part of a multiple birth, and 409,591 singleton controls. We replicated the association between FSHB, SMAD3 and twinning in the gene-based (but not SNP-based) test, which had been established in previous genome-wide association analyses in mothers with dizygotic twin offspring. Additionally, we report a novel genetic variant associated with multiple birth, rs428022 at 15q23 (p = 2.84 × 10^-8) close to two genes: PIAS1 and SKOR1. Finally, we identified meaningful genetic correlations between being part of a multiple birth and other phenotypes (anthropometric traits, health-related traits, and fertility-related measures). The outcomes of this study provide important new insights into the genetic aetiology of multiple births and fertility, and open up novel directions for fertility and reproduction research.

The Drosophila fussel gene is required for bitter gustatory neuron differentiation acting within an Rpd3 dependent chromatin modifying complex

Members of the Ski/Sno protein family are classified as proto-oncogenes and act as negative regulators of the TGF-ß/BMP-pathways in vertebrates and invertebrates. A newly identified member of this protein family is fussel (fuss), the Drosophila homologue of the human functional Smad suppressing elements (fussel-15 and fussel-18). We and others have shown that Fuss interacts with SMAD4 and that overexpression leads to a strong inhibition of Dpp signaling. However, to be able to characterize the endogenous Fuss function in Drosophila melanogaster, we have generated a number of state of the art tools including anti-Fuss antibodies, specific fuss-Gal4 lines and fuss mutant fly lines via the CRISPR/Cas9 system. Fuss is a predominantly nuclear, postmitotic protein, mainly expressed in interneurons and fuss mutants are fully viable without any obvious developmental phenotype. To identify potential target genes or cells affected in fuss mutants, we conducted targeted DamID experiments in adult flies, which revealed the function of fuss in bitter gustatory neurons. We fully characterized fuss expression in the adult proboscis and by using food choice assays we were able to show that fuss mutants display defects in detecting bitter compounds. This correlated with a reduction of gustatory receptor gene expression (Gr33a, Gr66a, Gr93a) providing a molecular link to the behavioral phenotype. In addition, Fuss interacts with Rpd3, and downregulation of rpd3 in gustatory neurons phenocopies the loss of Fuss expression. Surprisingly, there is no colocalization of Fuss with phosphorylated Mad in the larval central nervous system, excluding a direct involvement of Fuss in Dpp/BMP signaling. Here we provide a first and exciting link of Fuss function in gustatory bitter neurons. Although gustatory receptors have been well characterized, little is known regarding the differentiation and maturation of gustatory neurons. This work therefore reveals Fuss as a pivotal element for the proper differentiation of bitter gustatory neurons acting within a chromatin modifying complex.

A direct interaction between two Restless Legs Syndrome predisposing genes: MEIS1 and SKOR1

Restless Legs syndrome (RLS) is a common sleep disorder for which the genetic contribution remains poorly explained. In 2007, the first large scale genome wide association study (GWAS) identified three genomic regions associated with RLS. MEIS1, BTBD9 and MAP2K5/SKOR1 are the only known genes located within these loci and their association with RLS was subsequently confirmed in a number of follow up GWAS. Following this finding, our group reported the MEIS1 risk haplotype to be associated with its decreased expression at the mRNA and protein levels. Here we report the effect of the risk variants of the three other genes strongly associated with RLS. While these variants had no effect on the mRNA levels of the genes harboring them, we find that the homeobox transcription factor MEIS1 positively regulates the expression of the transcription co-repressor SKOR1. This regulation appears mediated through the binding of MEIS1 at two specific sites located in the SKOR1 promoter region and is modified by an RLS associated SNP in the promoter region of the gene. Our findings directly link MEIS1 and SKOR1, two significantly associated genes with RLS and also prioritize SKOR1 over MAP2K5 in the RLS associated intergenic region of MAP2K5/SKOR1 found by GWAS.

CORL Expression in the Drosophila Central Nervous System Is Regulated by Stage Specific Interactions of Intertwined Activators and Repressors

CORL proteins (SKOR in mice and Fussel in humans) are a subfamily of central nervous system (CNS) specific proteins related to Sno/Ski oncogenes. Their developmental and homeostatic roles are largely unknown. We previously showed that Drosophila CORL (dCORL; fussel in Flybase) functions between the Activin receptor Baboon and Ecdysone Receptor-B1 (EcR-B1) activation in mushroom body neurons of third instar larval brains. To better understand dCORL regulation and function we generated a series of reporter genes. We examined the embryonic and larval CNS and found that dCORL is regulated by stage specific interactions between intertwined activators and repressors spanning numerous reporters. The reporter AH.lacZ, which contains sequences 7-11kb upstream of dCORL exon1, reflects dCORL brain expression at all stages. Surprisingly, AH.lacZ was not detected in EcR-B1 expressing mushroom body neurons. In larvae AH.lacZ is coexpressed with Elav and the transcription factor Drifter in dILP2 insulin producing cells of the pars intercerebralis. The presence of dCORL in insulin producing cells suggests that dCORL functions non-autonomously in the regulation of EcR-B1 mushroom body activation via the modulation of insulin signaling. Overall, the high level of sequence conservation seen in all CORL/SKOR/Fussel family members and their common CNS specificity suggest that similarly complex regulation and a potential function in insulin signaling are associated with SKOR/Fussel proteins in mammals.

Transcriptional cofactors Ski and SnoN are major regulators of the TGF-β/Smad signaling pathway in health and disease

The transforming growth factor-β (TGF-β) family plays major pleiotropic roles by regulating many physiological processes in development and tissue homeostasis. The TGF-β signaling pathway outcome relies on the control of the spatial and temporal expression of >500 genes, which depend on the functions of the Smad protein along with those of diverse modulators of this signaling pathway, such as transcriptional factors and cofactors. Ski (Sloan-Kettering Institute) and SnoN (Ski novel) are Smad-interacting proteins that negatively regulate the TGF-β signaling pathway by disrupting the formation of R-Smad/Smad4 complexes, as well as by inhibiting Smad association with the p300/CBP coactivators. The Ski and SnoN transcriptional cofactors recruit diverse corepressors and histone deacetylases to repress gene transcription. The TGF-β/Smad pathway and coregulators Ski and SnoN clearly regulate each other through several positive and negative feedback mechanisms. Thus, these cross-regulatory processes finely modify the TGF-β signaling outcome as they control the magnitude and duration of the TGF-β signals. As a result, any alteration in these regulatory mechanisms may lead to disease development. Therefore, the design of targeted therapies to exert tight control of the levels of negative modulators of the TGF-β pathway, such as Ski and SnoN, is critical to restore cell homeostasis under the specific pathological conditions in which these cofactors are deregulated, such as fibrosis and cancer.

Proteins that repress molecular signaling through the transforming growth factor-beta (TGF-β) pathway offer promising targets for treating cancer and fibrosis. Marina Macías-Silva and colleagues from the National Autonomous University of Mexico in Mexico City review the ways in which a pair of proteins, called Ski and SnoN, interact with downstream mediators of TGF-β to inhibit the effects of this master growth factor. Aberrant levels of Ski and SnoN have been linked to diverse range of diseases involving cell proliferation run amok, and therapies that regulate the expression of these proteins could help normalize TGF-β signaling to healthier physiological levels. For decades, drug companies have tried to target the TGF-β pathway, with limited success. Altering the activity of these repressors instead could provide a roundabout way of remedying pathogenic TGF-β activity in fibrosis and oncology.

Iron, dopamine, genetics, and hormones in the pathophysiology of restless legs syndrome

Restless legs syndrome (RLS) is a common, chronic neurologic condition, which causes a persistent urge to move the legs in the evening that interferes with sleep. Human and animal studies have been used to study the pathophysiologic state of RLS and much has been learned about the iron and dopamine systems in relation to RLS. Human neuropathologic and imaging studies have consistently shown decreased iron in different brain regions including substantia nigra and thalamus. These same areas also demonstrate a state of relative dopamine excess. While it is not known how these changes in dopamine or iron produce the symptoms of RLS, genetic and hormone studies of RLS have identified other biologic systems or genes, such as the endogenous opioid and melanocortin systems and BTBD9 and MEIS1, that may explain some of the iron or dopamine changes in relation to RLS. This manuscript will review what is known about the pathophysiology of RLS, especially as it relates to changes in iron, dopamine, genetics, and hormonal systems.

Mapping the Chromatin State Dynamics in Myoblasts

Background

Genome-wide mapping reveals chromatin landscapes unique to cell states. Histone marks of regulatory genes involved in cell specification and organ development provide a powerful tool to map regulatory sequences. H3K4me3 marks promoter regions; H3K27me3 marks repressed regions, and Pol II presence indicates active transcription. The presence of both H3K4me3 and H3K27me3 characterize poised sequences, a common characteristic of genes involved in pattern formation during organogenesis.

Results

We used genome-wide profiling for H3K27me3, H3K4me3, and Pol II to map chromatin states in mouse embryonic day 12 forelimbs in wild type (control) and Pitx2-null mutant mice. We compared these data with previous gene expression studies from forelimb Lbx1⁺ migratory myoblasts and correlated Pitx2-dependent expression profiles and chromatin states. During forelimb development, several lineages including myoblast, osteoblast, neurons, angioblasts etc., require synchronized growth to form a functional limb. We identified 125 genes in the developing forelimb that are Pitx2-dependent. Genes involved in muscle specification and cytoskeleton architecture were positively regulated, while genes involved in axonal path finding were poised.

Conclusion

Our results have established histone modification profiles as a useful tool for identifying gene regulatory states in muscle development, and identified the role of Pitx2 in extending the time of myoblast progression, promoting formation of sarcomeric structures, and suppressing attachment of neuronal axons.

The Molecular Genetics of Restless Legs Syndrome

Restless legs syndrome (RLS) is a common sensorimotor trait defined by symptoms that interfere with sleep onset and maintenance in a clinically meaningful way. Nonvolitional myoclonus while awake and asleep is a sign of the disorder and an informative endophenotype. The genetic contributions to RLS/periodic leg movements are substantial, are among the most robust defined to date for a common disease, and account for much of the variance in disease expressivity. The disorder is polygenic, as revealed by recent genome-wide association studies. Experimental studies are revealing mechanistic details of how these common variants might influence RLS expressivity.

Exome analysis reveals differentially mutated gene signatures of stage, grade and subtype in breast cancers

Breast cancers exhibit highly heterogeneous molecular profiles. Although gene expression profiles have been used to predict the risks and prognostic outcomes of breast cancers, the high variability of gene expression limits its clinical application. In contrast, genetic mutation profiles would be more advantageous than gene expression profiles because genetic mutations can be stably detected and the mutational heterogeneity widely exists in breast cancer genomes. We analyzed 98 breast cancer whole exome samples that were sorted into three subtypes, two grades and two stages. The sum deleterious effect of all mutations in each gene was scored to identify differentially mutated genes (DMGs) for this case-control study. DMGs were corroborated using extensive published knowledge. Functional consequences of deleterious SNVs on protein structure and function were also investigated. Genes such as ERBB2, ESP8, PPP2R4, KIAA0922, SP4, CENPJ, PRCP and SELP that have been experimentally or clinically verified to be tightly associated with breast cancer prognosis are among the DMGs identified in this study. We also identified some genes such as ARL6IP5, RAET1E, and ANO7 that could be crucial for breast cancer development and prognosis. Further, SNVs such as rs1058808, rs2480452, rs61751507, rs79167802, rs11540666, and rs2229437 that potentially influence protein functions are observed at significantly different frequencies in different comparison groups. Protein structure modeling revealed that many non-synonymous SNVs have a deleterious effect on protein stability, structure and function. Mutational profiling at gene- and SNV-level revealed differential patterns within each breast cancer comparison group, and the gene signatures correlate with expected prognostic characteristics of breast cancer classes. Some of the genes and SNVs identified in this study show high promise and are worthy of further investigation by experimental studies.

New molecular medicine-based scar management strategies

Keloids and hypertrophic scars are prevalent disabling conditions with still suboptimal treatments. Basic science and molecular-based medicine research have contributed to unravel new bench-to-bedside scar therapies and to dissect the complex signalling pathways involved. Peptides such as the transforming growth factor beta (TGF-β) superfamily, with Smads, Ski, SnoN, Fussels, endoglin, DS-Sily, Cav-1p, AZX100, thymosin-β4 and other related molecules may emerge as targets to prevent and treat keloids and hypertrophic scars. The aim of this review is to describe the basic complexity of these new molecular scar management strategies and point out new fibrosis research lines.

Cold atmospheric plasma, a new strategy to induce senescence in melanoma cells

Over the past few years, the application of cold atmospheric plasma (CAP) in medicine has developed into an innovative field of research of rapidly growing importance. One promising new medical application of CAP is cancer treatment. Different studies revealed that CAP may potentially affect the cell cycle and cause cell apoptosis or necrosis in tumor cells dependent on the CAP device and doses. In this study, we used a novel hand-held and battery-operated CAP device utilizing the surface micro discharge (SMD) technology for plasma production in air and consequently analysed dose-dependent CAP treatment effects on melanoma cells. After 2 min of CAP treatment, we observed irreversible cell inactivation. Phospho-H2AX immunofluorescence staining and Flow cytometric analysis demonstrated that 2 min of CAP treatment induces DNA damage, promotes induction of Sub-G1 phase and strongly increases apoptosis. Further, protein array technology revealed induction of pro-apoptotic events like p53 and Rad17 phosphorylation of Cytochrome c release and activation of Caspase-3. Interestingly, using lower CAP doses with 1 min of treatment, almost no apoptosis was observed but long-term inhibition of proliferation. H3K9 immunofluorescence, SA-ß-Gal staining and p21 expression revealed that especially these low CAP doses induce senescence in melanoma cells. In summary, we observed differences in induction of apoptosis or senescence of tumor cells in respond to different CAP doses using a new CAP device. The mechanism of senescence with regard to plasma therapy was so far not described previously and is of great importance for therapeutic application of CAP.

Drosophila CORL is required for Smad2-mediated activation of Ecdysone Receptor expression in the mushroom body

CORL proteins (FUSSEL/SKOR proteins in humans) are related to Sno/Ski oncogenes but their developmental roles are unknown. We have cloned Drosophila CORL and show that its expression is restricted to distinct subsets of cells in the central nervous system. We generated a deletion of CORL and noted that homozygous individuals rarely survive to adulthood. Df(4)dCORL adult escapers display mushroom body (MB) defects and Df(4)dCORL larvae are lacking Ecdysone Receptor (EcR-B1) expression in MB neurons. This is phenocopied in CORL-RNAi and Smad2-RNAi clones in wild-type larvae. Furthermore, constitutively active Baboon (type I receptor upstream of Smad2) cannot stimulate EcR-B1 MB expression in Df(4)dCORL larvae, which demonstrates a formal requirement for CORL in Smad2 signaling. Studies of mouse Corl1 (Skor1) revealed that it binds specifically to Smad3. Overall, the data suggest that CORL facilitates Smad2 activity upstream of EcR-B1 in the MB. The conservation of neural expression and strong sequence homology of all CORL proteins suggests that this is a new family of Smad co-factors.

fussel (fuss)--A negative regulator of BMP signaling in Drosophila melanogaster

The TGF-β/BMP signaling cascades control a wide range of developmental and physiological functions in vertebrates and invertebrates. In Drosophila melanogaster, members of this pathway can be divided into a Bone Morphogenic Protein (BMP) and an Activin-ß (Act-ß) branch, where Decapentaplegic (Dpp), a member of the BMP family has been most intensively studied. They differ in ligands, receptors and transmitting proteins, but also share some components, such as the Co-Smad Medea (Med). The essential role of Med is to form a complex with one of the two activating Smads, mothers against decapentaplegic (Mad) or dSmad, and to translocate together to the nucleus where they can function as transcriptional regulators of downstream target genes. This signaling cascade underlies different mechanisms of negative regulation, which can be exerted by inhibitory Smads, such as daughters against decapentaplegic (dad), but also by the Ski-Sno family. In this work we identified and functionally analyzed a new member of the Ski/Sno-family, fussel (fuss), the Drosophila homolog of the human functional suppressing element 15 (fussel-15). fuss codes for two differentially spliced transcripts with a neuronal expression pattern. The proteins are characterized by a Ski-Sno and a SAND homology domain. Overexpression studies and genetic interaction experiments clearly reveal an interaction of fuss with members of the BMP pathway, leading to a strong repression of BMP-signaling. The protein interacts directly with Medea and seems to reprogram the Smad pathway through its influence upon the formation of functional Mad/Medea complexes. This leads amongst others to a repression of downstream target genes of the Dpp pathway, such as optomotor blind (omb). Taken together we could show that fuss exerts a pivotal role as an antagonist of BMP signaling in Drosophila melanogaster.

The MAP2K5-linked SNP rs2241423 is associated with BMI and obesity in two cohorts of Swedish and Greek children

Background

Recent genome-wide association studies have identified a single nucleotide polymorphism within the last intron of MAP2K5 associated with a higher body mass index (BMI) in adults. MAP2K5 is a component of the MAPK-family intracellular signaling pathways, responding to extracellular growth factors such as brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF). In this study, we examined the association of this variant in two cohorts of children from Sweden and Greece.

Methods

We examine the association of rs2241423 to BMI in a cohort of 474 Swedish children admitted for treatment of childhood obesity and 519 children matched for gender, ethnicity and socioeconomic background from the Stockholm area, as well as a cross-sectional cohort of 2308 Greek school children (Healthy Growth Study). Children were genotyped using a predesigned TaqMan polymorphism assay. Logistic regression was used to test for an association of rs2241423 to obesity in the cohort of Swedish children. Linear regression was used to test for an association of rs2241423 to BMI z-score and phenotypic measurements of body adiposity in the cohort of Greek children. Models were adjusted for age and gender. In the cohort of Greek children the model was also adjusted for stage of pubertal development.

Results

The minor allele of rs2241423, allele A, was associated with a protective effect against obesity in the cohort of Swedish children (p = 0.029, OR = 0.79 (95% CI: 0.64–0.98)), and with a lower BMI z-score in the cohort of Greek children (p = 0.028, β = −0.092). No association to phenotypic measurements of body fat distribution could be observed in our study.

Conclusions

rs2241423 was associated with BMI and obesity in two independent European cohorts suggesting a role for MAP2K5 in early weight regulation.

Death inducer-obliterator 1 (Dido1) is a BMP target gene and promotes BMP-induced melanoma progression

Bone morphogenetic proteins (BMPs) are known to play an important role in melanoma development and progression. However, the downstream targets of BMPs have not been investigated thus far. Therefore, we treated melanoma cell lines with the Smad-specific BMP inhibitor Dorsomorphin and performed a cDNA microarray. We identified death inducer-obliterator 1 (Dido1) as a BMP-specific Smad-regulated target gene, which was confirmed by qRT-PCR, immunofluorescence staining and electrophoretic mobility shift assay experiments. An analysis of Dido1 expression revealed an upregulation of Dido1 levels in melanoma cell lines and tissues compared with normal melanocytes. Colony-formation assays showed that siDido1-transfected cells formed significantly smaller colonies when grown in soft agar compared with control cells. In addition, fluorescence-activated cell sorting and western blot experiments revealed that transfection of melanoma cells with Dido1 small interfering RNAs led to an upregulation of apoptosis. Furthermore, cell migratory and invasive potentials were strongly reduced in siDido1-transfected cells compared with control cells. Finally, we demonstrated that Dido1 induces the expression of Integrin αV, thereby promoting the attachment, migration, invasion and apoptosis resistance of melanoma cells.

Fussel-15, a new player in wound healing, is deregulated in keloid and localized scleroderma

Dermal wound healing depends on highly complex interplay among various cytokines and cell types. Disruption of this process can result in impaired healing in the form of excessive scarring, as is the case in fibrotic diseases such as keloid and scleroderma. In the present study, we found Fussel-15, a new member of the Ski/Sno family of TGF-β/BMP signaling repressors, to be expressed in early wound healing and constantly overexpressed in keloid-derived and scleroderma-derived fibroblasts. Comparing the results of three-dimensional free-floating and attached-released in vitro wound healing assays, we observed that Fussel-15 is expressed during the migratory phase in the free-floating assay, indicating that Fussel-15 might play a role during fibroblast migration. Fussel-15-transfected fibroblasts showed greater migration ability in a scratch wound healing assay, compared with control-transfected cells. This migratory phenotype due to Fussel-15 was confirmed by increased peripheral F-actin localization and modifications in size, amount, and distribution of focal adhesion complexes, which were observed using F-actin and focal adhesion kinase (FAK) immunofluorescence staining, respectively. The present results suggest that expression of Fussel-15 during wound healing might promote fibroblast migration. Permanent expression of Fussel-15 in keloid and skin sclerosis fibroblasts could be involved in the pathogenesis of these conditions, but the molecular mechanism underlying this up-regulation remains to be determined.

Transposon mutagenesis with coat color genotyping identifies an essential role for Skor2 in sonic hedgehog signaling and cerebellum development

Correct development of the cerebellum requires coordinated sonic hedgehog (Shh) signaling from Purkinje to granule cells. How Shh expression is regulated in Purkinje cells is poorly understood. Using a novel tyrosinase minigene-tagged Sleeping Beauty transposon-mediated mutagenesis, which allows for coat color-based genotyping, we created mice in which the Ski/Sno family transcriptional co-repressor 2 (Skor2) gene is deleted. Loss of Skor2 leads to defective Purkinje cell development, a severe reduction of granule cell proliferation and a malformed cerebellum. Skor2 is specifically expressed in Purkinje cells in the brain, where it is required for proper expression of Shh. Skor2 overexpression suppresses BMP signaling in an HDAC-dependent manner and stimulates Shh promoter activity, suggesting that Skor2 represses BMP signaling to activate Shh expression. Our study identifies an essential function for Skor2 as a novel transcriptional regulator in Purkinje cells that acts upstream of Shh during cerebellum development.

MicroRNA miR-196a is a central regulator of HOX-B7 and BMP4 expression in malignant melanoma

Since bone morphogenetic proteins (BMPs) play an important role in melanoma progression, we aimed to determine the molecular mechanisms leading to overexpression of BMP4 in melanoma cells compared to normal melanocytes. With our experimental approach we revealed that loss of expression of a microRNA represents the starting point for a signaling cascade finally resulting in overexpression of BMP4 in melanoma cells. In detail, strongly reduced expression of the microRNA miR-196a in melanoma cells compared to healthy melanocytes leads to enhanced HOX-B7 mRNA and protein levels, which subsequently raise Ets-1 activity by inducing basic fibroblast growth factor (bFGF). Ets-1 finally accounts for induction of BMP4 expression. We were furthermore able to demonstrate that bFGF-mediated induction of migration is achieved via activation of BMP4, thus determining BMP4 as major modulator of migration in melanoma. In summary, our study provides insights into the early steps of melanoma progression and might thereby harbor therapeutic relevance.

The crystal structure of the Dachshund domain of human SnoN reveals flexibility in the putative protein interaction surface

The human SnoN is an oncoprotein that interacts with several transcription-regulatory proteins such as the histone-deacetylase, N-CoR containing co-repressor complex and Smad proteins. This study presents the crystal structure of the Dachshund homology domain of human SnoN. The structure reveals a groove composed of conserved residues with characteristic properties of a protein-interaction surface. A comparison of the 12 monomers in the asymmetric unit reveals the presence of two major conformations: an open conformation with a well accessible groove and a tight conformation with a less accessible groove. The variability in the backbone between the open and the tight conformations matches the differences seen in previously determined structures of individual Dachshund homology domains, suggesting a general plasticity within this fold family. The flexibility observed in the putative protein binding groove may enable SnoN to recognize multiple interaction partners.

SnoN in mammalian development, function and diseases

SnoN (Ski-novel protein) was discovered as a nuclear proto-oncogene on the basis of its ability to induce transformation of chicken and quail embryonic fibroblasts. As a crucial negative regulator of transforming growth factor-β (TGF-β) signaling and also an activator of p53, it plays an important role in regulating cell proliferation, senescence, apoptosis, and differentiation. Recent studies of its expression patterns and functions in mouse models and mammalian cells have revealed important functions of SnoN in normal epithelial development and tumorigenesis. Evidence suggests that SnoN has both pro-oncogenic and anti-oncogenic functions by modulating multiple signaling pathways. These studies suggest that SnoN may have broad functions in the development and homeostasis of embryonic and postnatal tissues.

Processing of MIA protein during melanoma cell migration

MIA (melanoma inhibitory activity) protein, identified as a small 11 kDa protein highly expressed and secreted by malignant melanoma cells, plays an important functional role in melanoma development, progression and tumor cell invasion. Recent data describe a direct interaction of MIA protein with cell adhesion receptors integrin alpha(4)beta(1) and integrin alpha(5)beta(1) and extracellular matrix molecules. By modulating integrin activity MIA protein mediates detachment of melanoma cells from surrounding structures resulting in enhanced invasive and migratory potential. However, until today a detailed understanding of the processes of MIA function is missing. In this study, we show that after binding of MIA protein to integrin alpha(5)beta(1), MIA protein is internalized together with this cell adhesion receptor at the cell rear. This mechanism enables tumor cells to migrate in a defined direction as appropriate for invasion processes. Treatment of melanoma cells with PKC-inhibitors strongly reduced internalization of MIA protein. Endocytosis is followed by dissociation of MIA-integrin complexes. In acidic vesicles MIA protein is degraded while integrins are recycled. Treatment of melanoma cells with MIA inhibitory peptides almost completely blocked the MIA protein uptake into cells. As MIA protein has a major contribution to the aggressive characteristics of malignant melanoma in particular to formation of metastasis, it is important to elucidate the MIA functional mechanism in tumor cells to find novel therapeutic strategies in the fight against skin cancer.

Ski and SnoN, potent negative regulators of TGF-beta signaling

Ski and the closely related SnoN were discovered as oncogenes by their ability to transform chicken embryo fibroblasts upon overexpression. While elevated expressions of Ski and SnoN have also been reported in many human cancer cells and tissues, consistent with their pro-oncogenic activity, emerging evidence also suggests a potential anti-oncogenic activity for both. In addition, Ski and SnoN have been implicated in regulation of cell differentiation, especially in the muscle and neuronal lineages. Multiple cellular partners of Ski and SnoN have been identified in an effort to understand the molecular mechanisms underlying the complex roles of Ski and SnoN. In this review, we summarize recent findings on the biological functions of Ski and SnoN, their mechanisms of action and how their levels of expression are regulated.

Ski regulates muscle terminal differentiation by transcriptional activation of Myog in a complex with Six1 and Eya3

Overexpression of the Ski pro-oncogene has been shown to induce myogenesis in non-muscle cells, to promote muscle hypertrophy in postnatal mice, and to activate transcription of muscle-specific genes. However, the precise role of Ski in muscle cell differentiation and its underlying molecular mechanism are not fully understood. To elucidate the involvement of Ski in muscle terminal differentiation, two retroviral systems were used to achieve conditional overexpression or knockdown of Ski in satellite cell-derived C2C12 myoblasts. We found that enforced expression of Ski promoted differentiation, whereas loss of Ski severely impaired it. Compromised terminal differentiation in the absence of Ski was likely because of the failure to induce myogenin (Myog) and p21 despite normal expression of MyoD. Chromatin immunoprecipitation and transcriptional reporter experiments showed that Ski occupied the endogenous Myog regulatory region and activated transcription from the Myog regulatory region upon differentiation. Transactivation of Myog was largely dependent on a MEF3 site bound by Six1, not on the binding site of MyoD or MEF2. Activation of the MEF3 site required direct interaction of Ski with Six1 and Eya3 mediated by the evolutionarily conserved Dachshund homology domain of Ski. Our results indicate that Ski is necessary for muscle terminal differentiation and that it exerts this role, at least in part, through its association with Six1 and Eya3 to regulate the Myog transcription.