OAZ regulates bone morphogenetic protein signaling through Smad6 activation

Halogenases: a palette of emerging opportunities for synthetic biology-synthetic chemistry and C-H functionalisation

The enzymatic generation of carbon-halogen bonds is a powerful strategy used by both nature and synthetic chemists to tune the bioactivity, bioavailability and reactivity of compounds, opening up the opportunity for selective C-H functionalisation. Genes encoding halogenase enzymes have recently been shown to transcend all kingdoms of life. These enzymes install halogen atoms into aromatic and less activated aliphatic substrates, achieving selectivities that are often challenging to accomplish using synthetic methodologies. Significant advances in both halogenase discovery and engineering have provided a toolbox of enzymes, enabling the ready use of these catalysts in biotransformations, synthetic biology, and in combination with chemical catalysis to enable late stage C-H functionalisation. With a focus on substrate scope, this review outlines the mechanisms employed by the major classes of halogenases, while in parallel, it highlights key advances in the utilisation of the combination of enzymatic halogenation and chemical catalysis for C-H activation and diversification.

Genome-wide interference of ZNF423 with B-lineage transcriptional circuitries in acute lymphoblastic leukemia

Aberrant expression of the transcriptional modulator and early B-cell factor 1 (EBF1) antagonist ZNF423 has been implicated in B-cell leukemogenesis, but its impact on transcriptional circuitries in lymphopoiesis has not been elucidated in a comprehensive manner. Herein, in silico analyses of multiple expression data sets on 1354 acute leukemia samples revealed a widespread presence of ZNF423 in various subtypes of acute lymphoblastic leukemia (ALL). Average expression of ZNF423 was highest in ETV6-RUNX1, B-other, and TCF3-PBX1 ALL followed by BCR-ABL, hyperdiploid ALL, and KMT2A-rearranged ALL. In a KMT2A-AFF1 pro-B ALL model, a CRISPR-Cas9-mediated genetic ablation of ZNF423 decreased cell viability and significantly prolonged survival of mice upon xenotransplantation. For the first time, we characterized the genome-wide binding pattern of ZNF423, its impact on the chromatin landscape, and differential gene activities in a B-lineage context. In general, chromatin-bound ZNF423 was associated with a depletion of activating histone marks. At the transcriptional level, EBF1-dependent transactivation was disrupted by ZNF423, whereas repressive and pioneering activities of EBF1 were not discernibly impeded. Unexpectedly, we identified an enrichment of ZNF423 at canonical EBF1-binding sites also in the absence of EBF1, which was indicative of intrinsic EBF1-independent ZNF423 activities. A genome-wide motif search at EBF1 target gene loci revealed that EBF1 and ZNF423 co-regulated genes often contain SMAD1/SMAD4-binding motifs as exemplified by the TGFB1 promoter, which was repressed by ZNF423 outcompeting EBF1 by depending on its ability to bind EBF1 consensus sites and to interact with EBF1 or SMADs. Overall, these findings underscore the wide scope of ZNF423 activities that interfere with B-cell lymphopoiesis and contribute to leukemogenesis.

The Classic Lobe Eye Phenotype of Drosophila Is Caused by Transposon Insertion-Induced Misexpression of a Zinc-Finger Transcription Factor

Drosophila Lobe (L) alleles were first discovered ∼100 years ago as spontaneous dominant mutants with characteristic developmental eye defects. However, the molecular basis for L dominant eye phenotypes has not been clearly understood. A previous work reported identification of CG10109/PRAS40 as the L gene, but subsequent analyses suggested that PRAS40 may not be related to L Here, we revisited the L gene to clarify this discrepancy and understand the basis for the dominance of L mutations. Genetic analysis localized the L gene to Oaz, which encodes a homolog of the vertebrate zinc finger protein 423 (Zfp423) family transcriptional regulators. We demonstrate that RNAi knockdown of Oaz almost completely restores all L dominant alleles tested. Lrev6-3 , a revertant allele of the L2 dominant eye phenotype, has an inframe deletion in the Oaz coding sequence. Molecular analysis of L dominant mutants identified allele-specific insertions of natural transposons (roo[ ]L1 , hopper[ ]L5 , and roo[ ]Lr ) or alterations of a preexisting transposon (L2 -specific mutations in roo[ ]Mohr) in the Oaz region. In addition, we generated additional L2 -reversion alleles by CRISPR targeting at Oaz These new loss-of-function Oaz mutations suppress the dominant L eye phenotype. Oaz protein is not expressed in wild-type eye disc but is expressed ectopically in L2/+ mutant eye disc. We induced male recombination between Oaz-GAL4 insertions and the L2 mutation through homologous recombination. By using the L2 -recombined GAL4 reporters, we show that Oaz-GAL4 is expressed ectopically in L2 eye imaginal disc. Taken together, our data suggest that neomorphic L eye phenotypes are likely due to misregulation of Oaz by spontaneous transposon insertions.

ZNF423 patient variants, truncations, and in-frame deletions in mice define an allele-dependent range of midline brain abnormalities

Interpreting rare variants remains a challenge in personal genomics, especially for disorders with several causal genes and for genes that cause multiple disorders. ZNF423 encodes a transcriptional regulatory protein that intersects several developmental pathways. ZNF423 has been implicated in rare neurodevelopmental disorders, consistent with midline brain defects in Zfp423-mutant mice, but pathogenic potential of most patient variants remains uncertain. We engineered ~50 patient-derived and small deletion variants into the highly-conserved mouse ortholog and examined neuroanatomical measures for 791 littermate pairs. Three substitutions previously asserted pathogenic appeared benign, while a fourth was effectively null. Heterozygous premature termination codon (PTC) variants showed mild haploabnormality, consistent with loss-of-function intolerance inferred from human population data. In-frame deletions of specific zinc fingers showed mild to moderate abnormalities, as did low-expression variants. These results affirm the need for functional validation of rare variants in biological context and demonstrate cost-effective modeling of neuroanatomical abnormalities in mice.

ZNF423: A New Player in Estrogen Receptor-Positive Breast Cancer

Preventive therapy can target hormone-responsive breast cancer (BC) by treatment with selective estrogen receptor modulators (SERMs) and reduce the incidence of BC. Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) with relevant predictive values, SNPs in the ZNF423 gene were associated with decreased risk of BC during SERM therapy, and SNPs in the Cathepsin O gene with an increased risk. ZNF423, which was not previously associated with BC is a multifunctional transcription factor known to have a role in development, neurogenesis, and adipogenesis and is implicated in other types of cancer. ZNF423 is transcriptionally controlled by the homolog ZNF521, early B cell factor transcription factor, epigenetic silencing of the promoter by CpG island hyper-methylation, and also by ZNF423 itself in an auto-regulatory loop. In BC cells, ZNF423 expression is found to be induced by estrogen, dependent on the binding of the estrogen receptor and calmodulin-like 3 to SNPs in ZNP423 intronic sites in proximity to consensus estrogen response elements. ZNF423 has also been shown to play a mechanistic role by trans-activating the tumor suppressor BRCA1 and thus modulating the DNA damage response. Even though recent extensive trial studies did not classify these SNPs with the highest predictive values, for inclusion in polygenic SNP analysis, the mechanism unveiled in these studies has introduced ZNF423 as a factor important in the control of the estrogen response. Here, we aim at providing an overview of ZNF423 expression and functional role in human malignancies, with a specific focus on its implication in hormone-responsive BC.

Zfp423/ZNF423 regulates cell cycle progression, the mode of cell division and the DNA-damage response in Purkinje neuron progenitors

The Zfp423/ZNF423 gene encodes a 30-zinc-finger transcription factor involved in key developmental pathways. Although null Zfp423 mutants develop cerebellar malformations, the underlying mechanism remains unknown. ZNF423 mutations are associated with Joubert Syndrome, a ciliopathy causing cerebellar vermis hypoplasia and ataxia. ZNF423 participates in the DNA-damage response (DDR), raising questions regarding its role as a regulator of neural progenitor cell cycle progression in cerebellar development. To characterize in vivo the function of ZFP423 in neurogenesis, we analyzed allelic murine mutants in which distinct functional domains are deleted. One deletion impairs mitotic spindle orientation, leading to premature cell cycle exit and Purkinje cell (PC) progenitor pool deletion. The other deletion impairs PC differentiation. In both mutants, cell cycle progression is remarkably delayed and DDR markers are upregulated in cerebellar ventricular zone progenitors. Our in vivo evidence sheds light on the domain-specific roles played by ZFP423 in different aspects of PC progenitor development, and at the same time strengthens the emerging notion that an impaired DDR may be a key factor in the pathogenesis of JS and other ciliopathies.

Regulation of TGF-β Family Signaling by Inhibitory Smads

Inhibitory Smads (I-Smads) have conserved carboxy-terminal MH2 domains but highly divergent amino-terminal regions when compared with receptor-regulated Smads (R-Smads) and common-partner Smads (co-Smads). Smad6 preferentially inhibits Smad signaling initiated by the bone morphogenetic protein (BMP) type I receptors ALK-3 and ALK-6, whereas Smad7 inhibits both transforming growth factor β (TGF-β)- and BMP-induced Smad signaling. I-Smads also regulate some non-Smad signaling pathways. Here, we discuss the vertebrate I-Smads, their roles as inhibitors of Smad activation and regulators of receptor stability, as scaffolds for non-Smad signaling, and their possible roles in the nucleus. We also discuss the posttranslational modification of I-Smads, including phosphorylation, ubiquitylation, acetylation, and methylation.

Restored immunosuppressive effect of mesenchymal stem cells on B cells after olfactory 1/early B cell factor-associated zinc-finger protein down-regulation in patients with systemic lupus erythematosus

OBJECTIVE

To evaluate whether olfactory 1/early B cell factor-associated zinc-finger protein (OAZ), a candidate lupus susceptibility gene involved in antinuclear antibody (ANA) production, plays a role in the regulation of B cells by mesenchymal stem cells (MSCs).

METHODS

MSCs derived from the bone marrow of patients with systemic lupus erythematosus (SLE) and healthy control subjects were expanded and incubated with small interfering RNAs specific for OAZ or a nontargeting sequence. Knockdown of messenger RNA levels of OAZ and its downstream genes was measured using real-time polymerase chain reaction, and protein levels of chemokine/cytokine and immunoglobulins were determined by enzyme-linked immunosorbent assay or Western blotting. The effects of modulating the OAZ levels in MSCs, by either silencing or overexpression, on B cell proliferation and terminal differentiation were assessed by coculturing MSCs with mouse spleen cells.

RESULTS

OAZ gene expression was highly enriched in MSCs compared with peripheral blood leukocytes and was increased in patients with SLE compared with control subjects. After the silencing of OAZ expression, SLE MSCs could regain the ability to inhibit B cell proliferation and terminal differentiation, as indicated by decreased percentages of bromodeoxyuridine-positive cells and CD138+ cells as well as decreased levels of IgG, IgM, and ANAs. The level of CCL2 was increased after OAZ knockdown, while anti-CCL2 antibodies completely counteracted the effect of OAZ silencing. Umbilical cord-derived normal MSCs that overexpressed OAZ had a diminished ability to inhibit B cell proliferation and terminal differentiation.

CONCLUSION

OAZ down-regulation could restore the impaired function of SLE MSCs in the immune regulation of B cells, contributing to a reduction in ANA levels. OAZ might represent a new target for therapy in patients with SLE.

ZNF423: Transcriptional modulation in development and cancer

Krüppel-like zinc finger proteins are versatile players in biology that have been implicated in mammalian development and disease. Among these proteins, ZNF423 and its mouse ortholog Zfp423 were initially implicated in midline patterning of the central nervous system but have emerged as critical transcriptional modulators in cancer. Epigenetically uncurbed ZNF423 interferes with lymphopoiesis by sequestration of the essential early B-cell factor 1 (EBF1) causing B-cell maturation arrest, a hallmark of acute lymphoblastic leukemia. Conversely, its presence in neuroblastoma, a primitive neuroectodermal tumor of childhood, allows retinoic acid-induced differentiation and is associated with a favorable outcome of neuroblastoma patients. Such opposing effects may be explained by the cellular context, but also by the multifunctionality of ZNF423 that is mediated by 30 zinc fingers forming various functional domains. This review summarizes current knowledge of ZNF423, focusing on its role in development and cancer.

Expression profiling and functional implications of a set of zinc finger proteins, ZNF423, ZNF470, ZNF521, and ZNF780B, in primary osteoarthritic articular chondrocytes

Articular chondrocytes are responsible for the maintenance of healthy articulations; indeed, dysregulation of their functions, including the production of matrix proteins and matrix-remodeling proteases, may result in fraying of the tissue and development of osteoarthritis (OA). To explore transcriptional mechanisms that contribute to the regulation of chondrocyte homeostasis and may be implicated in OA development, we compared the gene expression profile of a set of zinc finger proteins potentially linked to the control of chondrocyte differentiation and/or functions (ZNF423, ZNF470, ZNF521, and ZNF780B) in chondrocytes from patients affected by OA and from subjects not affected by OA. This analysis highlighted a significantly lower expression of the transcript encoding ZNF423 in chondrocytes from OA, particularly in elderly patients. Interestingly, this decrease was mirrored by the similarly reduced expression of PPARγ, a known target of ZNF423 with anti-inflammatory and chondroprotective properties. The ZNF521 mRNA instead was abundant in all primary chondrocytes studied; the RNAi-mediated silencing of this gene significantly altered the COL2A/COL1 expression ratio, associated with the maintenance of the differentiated phenotype, in chondrocytes cultivated in alginate beads. These results suggest a role for ZNF423 and ZNF521 in the regulation of chondrocyte homeostasis and warrant further investigations to elucidate their mechanism of action.

Modifier genes and non-genetic factors reshape anatomical deficits in Zfp423-deficient mice

Development of neural circuitry depends on the integration of signaling pathways to coordinate specification, proliferation and differentiation of cell types in the right number, in the right place, at the right time. Zinc finger protein 423 (Zfp423), a 30-zinc finger transcription factor, forms alternate complexes with components of several developmental signaling pathways, suggesting it as a point of signal integration during brain development. We previously showed that mice lacking Zfp423 have reduced proliferation of cerebellar precursor cells, resulting in complete loss of vermis and variable hypoplasia of cerebellar hemispheres. Here, we show that Zfp423(-/-) hemisphere malformations are shaped by both genetic and non-genetic factors, producing distinct phenotype distributions in different inbred genetic backgrounds. In genetic mapping studies, we identify four additive modifier loci (Amzn1-4) and seven synthetically interacting loci (Smzn1.1-3.1) that together explain approximately one-third of the phenotypic variance. Strain-specific sequence polymorphism and expression data provide a reduced list of functional variant candidate genes at each modifier locus. Environmental covariates add only modest explanatory power, suggesting an additional stochastic component. These results provide a comprehensive analysis of sources of phenotype variation in a model of hindbrain malformation.

The homeobox transcription factor VentX controls human macrophage terminal differentiation and proinflammatory activation

Macrophages are critical players in both innate and adaptive immunity. While the exogenous signaling events leading to the terminal differentiation of macrophages from monocytes have been studied extensively, the underlying intracellular transcriptional mechanisms remain poorly understood. Here we report that the homeobox transcription factor VentX plays a pivotal role in human macrophage terminal differentiation and proinflammatory function. Our study showed that VentX expression was upregulated upon human primary monocyte-to-macrophage differentiation induced by cytokines such as M-CSF, GM-CSF, and IL-3. Moreover, ablation of VentX expression in primary monocytes profoundly impaired their differentiation to macrophages, and ectopic expression of VentX in a myeloid progenitor cell line triggered its differentiation with prominent macrophage features. Further analysis revealed that VentX was pivotal for the proinflammatory response of terminally differentiated macrophages. Mechanistically, VentX was found to control expression of proteins key to macrophage differentiation and activation, including M-CSF receptor. Importantly, preliminary analysis of gene expression in leukocytes from patients with autoimmune diseases revealed a strong correlation between levels of VentX and those of proinflammatory cytokines. Our results provide mechanistic insight into the crucial roles of VentX in macrophage differentiation and proinflammatory activation and suggest that dysregulation of VentX may play a role in the pathogenesis of autoimmune diseases.

ZFP423 coordinates Notch and bone morphogenetic protein signaling, selectively up-regulating Hes5 gene expression

Zinc finger protein 423 encodes a 30 Zn-finger transcription factor involved in cerebellar and olfactory development. ZFP423 is a known interactor of SMAD1-SMAD4 and of Collier/Olf-1/EBF proteins, and acts as a modifier of retinoic acid-induced differentiation. In the present article, we show that ZFP423 interacts with the Notch1 intracellular domain in mammalian cell lines and in Xenopus neurula embryos, to activate the expression of the Notch1 target Hes5/ESR1. This effect is antagonized by EBF transcription factors, both in cultured cells and in Xenopus embryos, and amplified in vitro by BMP4, suggesting that ZFP423 acts to integrate BMP and Notch signaling, selectively promoting their convergence onto the Hes5 gene promoter.

A survey of well conserved families of C2H2 zinc-finger genes in Daphnia

Background

A recent comparative genomic analysis tentatively identified roughly 40 orthologous groups of C2H2 Zinc-finger proteins that are well conserved in "bilaterians" (i.e. worms, flies, and humans). Here we extend that analysis to include a second arthropod genome from the crustacean, Daphnia pulex.

Results

Most of the 40 orthologous groups of C2H2 zinc-finger proteins are represented by just one or two proteins within each of the previously surveyed species. Likewise, Daphnia were found to possess a similar number of orthologs for all of these small orthology groups. In contrast, the number of Sp/KLF homologs tends to be greater and to vary between species. Like the corresponding mammalian Sp/KLF proteins, most of the Drosophila and Daphnia homologs can be placed into one of three sub-groups: Class I-III. Daphnia were found to have three Class I proteins that roughly correspond to their Drosophila counterparts, dSP1, btd, CG5669, and three Class II proteins that roughly correspond to Luna, CG12029, CG9895. However, Daphnia have four additional KLF-Class II proteins that are most similar to the vertebrate KLF1/2/4 proteins, a subset not found in Drosophila. Two of these four proteins are encoded by genes linked in tandem. Daphnia also have three KLF-Class III members, one more than Drosophila. One of these is a likely Bteb2 homolog, while the other two correspond to Cabot and KLF13, a vertebrate homolog of Cabot.

Conclusion

Consistent with their likely roles as fundamental determinants of bilaterian form and function, most of the 40 groups of C2H2 zinc-finger proteins are conserved in kind and number in Daphnia. However, the KLF family includes several additional genes that are most similar to genes present in vertebrates but missing in Drosophila.

VentX, a novel lymphoid-enhancing factor/T-cell factor-associated transcription repressor, is a putative tumor suppressor

Lymphoid-enhancing factor/T-cell factors (LEF1/TCF) are a high-mobility group of transcriptional factors that play essential roles in cell fate determination during early embryogenesis and ontogenesis. Aberrant activations of LEF1/TCF-mediated transcription have been implicated in a variety of malignancies. Our recent studies on vertebrate embryogenesis identified Xom, a homeobox protein of the bone morphogenetic protein 4 pathway, as a novel LEF/TCF-associated transcriptional modulator. Here, we report that VentX, a human Xom homologue, is a LEF/TCF-associated inhibitor of canonical Wnt/beta-catenin signaling and a negative regulator of cell proliferation. VentX is predominantly expressed in hematopoietic cells, and its expression is significantly downregulated in chronic lymphocytic leukemia. Altered expression of VentX is associated with corresponding changes of LEF/TCF target oncogenes such as cyclin D1, suggesting a potential role of VentX in the clinical behavior of hematopoietic malignancies.

Molecular basis for antagonism between PDGF and the TGFbeta family of signalling pathways by control of miR-24 expression

Modulation of the vascular smooth-muscle-cell (vSMC) phenotype from a quiescent 'contractile' phenotype to a proliferative 'synthetic' phenotype has been implicated in vascular injury repair, as well as pathogenesis of vascular proliferative diseases. Both bone morphogenetic protein (BMP) and transforming growth factor-beta (TGFbeta)-signalling pathways promote a contractile phenotype, while the platelet-derived growth factor-BB (PDGF-BB)-signalling pathway promotes a switch to the synthetic phenotype. Here we show that PDGF-BB induces microRNA-24 (miR-24), which in turn leads to downregulation of Tribbles-like protein-3 (Trb3). Repression of Trb3 coincides with reduced expression of Smad proteins and decrease in BMP and TGFbeta signalling, promoting a synthetic phenotype in vSMCs. Inhibition of miR-24 by antisense oligonuclotides abrogates the downregulation of Trb3 as well as pro-synthetic activity of the PDGF-signalling pathway. Thus, this study provides a molecular basis for the antagonism between the PDGF and TGFbeta pathways, and its effect on the control of the vSMC phenotype.

The regulation of TGFbeta signal transduction

Transforming growth factor beta (TGFbeta) pathways are implicated in metazoan development, adult homeostasis and disease. TGFbeta ligands signal via receptor serine/threonine kinases that phosphorylate, and activate, intracellular Smad effectors as well as other signaling proteins. Oligomeric Smad complexes associate with chromatin and regulate transcription, defining the biological response of a cell to TGFbeta family members. Signaling is modulated by negative-feedback regulation via inhibitory Smads. We review here the mechanisms of TGFbeta signal transduction in metazoans and emphasize events crucial for embryonic development.

Fingering modulators of retinoic acid signaling identifies new prognostic marker for neuroblastoma

Properly designed genome-wide screening strategies can provide new insights into biological processes and/or biomarkers for malignant diseases. In this issue of Cancer Cell, Huang et al. demonstrate that the Krüppel zinc-finger protein ZNF423 is critical for retinoic acid signaling and is likely a favorable prognostic marker for neuroblastoma.

ZNF423 is critically required for retinoic acid-induced differentiation and is a marker of neuroblastoma outcome

Retinoids play key roles in differentiation, growth arrest, and apoptosis and are increasingly being used in the clinic for the treatment of a variety of cancers, including neuroblastoma. Here, using a large-scale RNA interference-based genetic screen, we identify ZNF423 (also known as Ebfaz, OAZ, or Zfp423) as a component critically required for retinoic acid (RA)-induced differentiation. ZNF423 associates with the RARalpha/RXRalpha nuclear receptor complex and is essential for transactivation in response to retinoids. Downregulation of ZNF423 expression by RNA interference in neuroblastoma cells results in a growth advantage and resistance to RA-induced differentiation, whereas overexpression of ZNF423 leads to growth inhibition and enhanced differentiation. Finally, we show that low ZNF423 expression is associated with poor disease outcome in neuroblastoma patients.

Regulation of TGF-beta signaling by Smad7

Transforming growth factor (TGF)-β is a pleiotropic cytokine regulating a variety of cellular processes such as cell growth, differentiation, apoptosis, migration, cell adhesion, and immune response. In the well-understood classical TGF-β signaling pathway, TGF-β activates Smad signalling via its two cell surface receptors such as TβRII and ALK5/TβRI, leading to Smad-mediated transcriptional regulation. In addition, TGF-β may also activate other signaling pathways like mitogen-activated protein kinase, PI3K, etc. The signaling of TGF-β is finely regulated at different levels. Inhibitory Smads, including Smad6 and Smad7, are key regulators of TGF-β/bone morphogenetic protein (BMP) signaling by negative feedback loops. They can form stable complexes with activated type I receptors and thereby blocking the phosphorylation of R-Smads, or recruit ubiquitin E3 ligases, such as Smurf1/2, resulting in the ubiquitination and degradation of the activated type I receptors. Besides, these inhibitory Smad proteins also inhibit TGF-β/BMP signaling in the nucleus by interacting with transcriptional repressors, such as histone deacetylases, Hoxc-8, and CtBP, or disrupting the formation of the TGF-β-induced functional Smad-DNA complexes. Smad7 is in turn regulated by different stimuli, including TGF-β, IFN-γ, TNF-α as well as ultraviolet and TPA, and mediates the crosstalk between TGF-β and other signaling pathways. Deregulation of Smad7 expression has been associated with various human diseases, such as tissue fibrosis, inflammatory disease as well as carcinogenesis. Overexpression of Smad7 has been shown to antagonize TGF-β-mediated fibrosis, carcinogenesis, and inflammation, suggesting a therapeutic potential of Smad7 to treat these diseases.

Expression of the calcium-binding protein S100P is regulated by bone morphogenetic protein in pancreatic duct epithelial cell lines

We previously reported that bone morphogenetic protein (BMP)-4 induces epithelial-mesenchymal transition in a pancreatic cancer cell line. To further investigate the detailed molecular mechanism of BMP action in pancreatic cancer, we carried out comprehensive microarray analysis in Panc-1 cells. The microarray analysis elucidated novel BMP target genes, and among them, the calcium-binding protein S100P was identified as an upregulated gene. S100P induction by BMP4 was confirmed by real-time reverse transcription-polymerase chain reaction and western blot analysis in Panc-1 and HPDE cells. Short interfering RNA-based knockdown of S100P expression sufficiently repressed BMP4-induced cell migration in Panc-1 cells. Because Panc-1 and HPDE cells express wild-type Smad4, we hypothesized that Smad4 might be indispensable for S100P induction by BMP4. S100P induction by BMP4 was not observed in the Smad4-null cell line BxPC3, and was sufficiently attenuated in short interfering RNA-based Smad4-knockdown Panc-1 cells. Interestingly, detailed promoter analysis revealed that upregulation of S100P by BMP4 was independent of the Smad-binding element, indicating that an additional unknown downstream factor of the Smad4-dependent pathway is necessary for this induction. These findings are the first of their kind, and this Smad4-dependent regulation of S100P by BMP signaling might explain the migratory mechanism of cancer cells, which is still unknown.

Control of phenotypic plasticity of smooth muscle cells by bone morphogenetic protein signaling through the myocardin-related transcription factors

Vascular smooth muscle cells (VSMCs), unlike other muscle cells, do not terminally differentiate. In response to injury, VSMCs change phenotype, proliferate, and migrate as part of the repair process. Dysregulation of this plasticity program contributes to the pathogenesis of several vascular disorders, such as atherosclerosis, restenosis, and hypertension. The discovery of mutations in the gene encoding BMPRII, the type II subunit of the receptor for bone morphogenetic proteins (BMPs), in patients with pulmonary arterial hypertension (PAH) provided an indication that BMP signaling may affect the homeostasis of VSMCs and their phenotype modulation. Here we report that BMP signaling potently induces SMC-specific genes in pluripotent cells and prevents dedifferentiation of arterial SMCs. The BMP-induced phenotype switch requires intact RhoA/ROCK signaling but is not blocked by inhibitors of the TGFbeta and PI3K/Akt pathways. Furthermore, nuclear localization and recruitment of the myocardin-related transcription factors (MRTF-A and MRTF-B) to a smooth muscle alpha-actin promoter is observed in response to BMP treatment. Thus, BMP signaling modulates VSMC phenotype via cross-talk with the RhoA/MRTFs pathway, and may contribute to the development of the pathological characteristics observed in patients with PAH and other obliterative vascular diseases.

The utility of MAS5 expression summary and detection call algorithms

BACKGROUND

Used alone, the MAS5.0 algorithm for generating expression summaries has been criticized for high False Positive rates resulting from exaggerated variance at low intensities.

RESULTS

Here we show, with replicated cell line data, that, when used alongside detection calls, MAS5 can be both selective and sensitive. A set of differentially expressed transcripts were identified that were found to be changing by MAS5, but unchanging by RMA and GCRMA. Subsequent analysis by real time PCR confirmed these changes. In addition, with the Latin square datasets often used to assess expression summary algorithms, filtered MAS5.0 was found to have performance approaching that of its peers.

CONCLUSION

When used alongside detection calls, MAS5 is a sensitive and selective algorithm for identifying differentially expressed genes.

Zfp423/OAZ participates in a developmental switch during olfactory neurogenesis

The coordination of gene expression is critical for cell differentiation and the subsequent establishment of tissue function. We show here that a multiple zinc finger transcription factor, Zfp423/OAZ, is transiently expressed in newly differentiating olfactory-receptor neurons (ORNs) and has a key role in coordinating the expression of immature and mature stage-specific genes. OAZ deletion in mice impairs aspects of ORN differentiation, particularly the patterns of axonal projection to the olfactory bulb. OAZ gain-of-function experiments show that sustained OAZ expression throughout ORN maturation arrests ORN development at an immature stage and alters OR gene expression. Importantly, reintroducing OAZ expression in mature ORNs suppresses mature marker expression and reactivates immature-specific markers. Together, these experiments suggest that OAZ participates in a developmental switch regulating the transition from differentiation to maturation in ORNs.

Early hematopoietic zinc finger protein-zinc finger protein 521: a candidate regulator of diverse immature cells

The early hematopoietic zinc finger protein/zinc finger protein 521 (EHZF/ZNF521) is a recently identified, 1131 amino-acid-long nuclear factor that contains 30 zinc fingers distributed in clusters throughout its sequence. A 13-AA motif, that binds to components of the nuclear remodelling and histone deacetylation (NuRD) complex and is conserved in several trascriptional co-repressors, is located at the amino-terminal end of the molecule. EHZF/ZNF521 expression is high in the most immature cells of the haematopoietic system and declines with differentiation. Its transcript is also abundant in brain, particularly in the cerebellum. Its murine counterpart, Evi3/Zfp521, is enriched in haematopoietic and neural stem cells, in cerebellar granule neuron precursors and in the developing striatum. Enforced expression of EHZF/ZNF521 in haematopoietic progenitors results in their expansion and in inhibition of differentiation. EHZF/ZNF521 is a member of the BMP signalling pathway and an inhibitor of the transcription factor OLF1/EBF1, implicated in the differentiation of neural progenitors and in the specification of the B-cell lineage. EHZF expression is observed in most acute myelogenous leukaemias and is particularly high in those with rearrangements of the MLL gene, where EHZF may contribute to the leukaemic phenotype. EHZF/ZNF521 is also abundant in medulloblastomas and other brain tumours. Taken together, the data available suggest a possible role for this factor in development, stem cell regulation and oncogenesis.

The transcription factor Zfp423/OAZ is required for cerebellar development and CNS midline patterning

The dorsal midline structure is critical for patterning the developing central nervous system (CNS). We show here that Zfp423/OAZ, a multiple zinc-finger transcription factor involved in both OE/EBF and BMP-signaling pathways, is required for the proper formation of forebrain and hindbrain midline structures. During embryogenesis, OAZ is highly expressed at the dorsal neuroepithelium flanking the roof plate. OAZ-deficient mice are ataxic, attributed to the reduction of the cerebellar vermis and some regions of the hemispheres. Characterization of postnatal cerebellar development shows defects in Purkinje cell differentiation and granule cell proliferation. In the forebrain, dorsal telencephalic commissural neurons project axons, but these axons fail to cross the midline and midline glial cells are abnormally distributed. Moreover, there are malformations in midline structures including the septum, thalamus and hypothalamus, suggesting a pivotal role of OAZ in CNS midline patterning.

BMP2 and BMP6 control p57Kip2 expression and cell growth arrest/terminal differentiation in normal primary human epidermal keratinocytes

Functional studies of the canonical Bone Morphogenetic Protein (BMP) signalling pathway in human epidermal keratinocytes have been limited to the immortalized and p53-mutated HaCaT cells and are primarily dependent on BMP6 treatment in mouse epidermal keratinocytes. Despite these insightful analyses, the molecular mechanism underlying the role of BMP signalling in the precise balance between growth arrest and terminal differentiation of keratinocytes still remains not clearly defined. The current study first investigated the hitherto uncharacterized status and functions of BMP signalling in normal human keratinocytes by using three independent strains of primary interfollicular epidermal keratinocytes. Then we provided data demonstrating the role of BMP2 compared to BMP6 in the inhibition of growth and induction of subsequent terminal differentiation of these cells. A second relevant finding is based on the clonal analysis of colony types present in untreated and BMP2/6-treated cultures in absence of EGF. BMP treatment results in the clonal transition from proliferative to abortive colonies, suggesting that BMP signalling most likely inhibits stem cell proliferation and triggers cell cycle exit from transit amplifying cells. Third, we showed evidence that, of the three members of the Cip/Kip family of cyclin-dependent kinase inhibitors, only p57(Kip2) and p21(Cip1) have a BMP2/6-induced expression. One mechanism of inhibition of cell proliferation involves p57(Kip2) as an immediate early response, in contradistinction with p21(Cip1) which largely depends on de novo protein synthesis for its effect to proceed. All together, these results clarify the BMP signalling status in normal primary human keratinocytes and support a new mechanism of inhibition of the proliferation of interfollicular epidermal keratinocytes coupled with induction of their terminal differentiation following BMP2 or BMP6 addition.

Zfp423 controls proliferation and differentiation of neural precursors in cerebellar vermis formation

Neural stem cells and progenitors in the developing brain must choose between proliferation with renewal and differentiation. Defects in navigating this choice can result in malformations or cancers, but the genetic mechanisms that shape this choice are not fully understood. We show by positional cloning that the 30-zinc finger transcription factor Zfp423 (OAZ) is required for patterning the development of neuronal and glial precursors in the developing brain, particularly in midline structures. Mutation of Zfp423 results in loss of the corpus callosum, reduction of hippocampus, and a malformation of the cerebellum reminiscent of human Dandy-Walker patients. Within the cerebellum, Zfp423 is expressed in both ventricular and external germinal zones. Loss of Zfp423 results in diminished proliferation by granule cell precursors in the external germinal layer, especially near the midline, and abnormal differentiation and migration of ventricular zone-derived neurons and Bergmann glia.

BMP-dependent activation of caspase-9 and caspase-8 mediates apoptosis in pulmonary artery smooth muscle cells

Germ line mutations in the bone morphogenetic protein (BMP) receptor type II (BMPRII) gene have been found in >50% of familial idiopathic pulmonary arterial hypertension (IPAH) patients and in 30% of sporadic cases of IPAH. Mutations of BMPRII occur in the extracellular ligand-binding domain, in the cytoplasmic serine/threonine kinase domain, or in the long carboxy terminus domain of unknown function. In this study, we demonstrate that BMPs promote apoptotic cell death in normal human pulmonary artery smooth muscle cells (PASMCs) by activation of caspases-3, -8, and -9, cytochrome c release, and downregulation of Bcl-2. Normal PASMCs expressing a kinase domain mutant or a carboxy-terminal domain deletion mutant of BMPRII identified in IPAH patients are resistant to BMP-mediated apoptosis. This dominant-negative effect may act in heterozygous patients and lead to the development of the pulmonary vascular medial hypertrophy found in IPAH patients. Our study also demonstrates an essential role of the carboxy terminus domain of BMPRII in the activation of the apoptotic signaling cascade.