Cloning and functional analysis of a family of nuclear matrix transcription factors (NP/NMP4) that regulate type I collagen expression in osteoblasts

TCF3::ZNF384 induces steroid resistance in B-cell precursor acute lymphoblastic leukemia cells

BACKGROUND

ZNF384 rearrangements (ZNF384-r) are associated with distinct subgroups of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) and the mixed phenotype of acute leukemia. Types of BCP-ALL with ZNF384-r exhibit common immunophenotypic characteristics, whereas their clinical features are not uniform and TCF3::ZNF384-positive patients show a significantly poorer steroid response and higher frequency of relapse, while EP300::ZNF384-positive patients exhibit a favorable response to conventional chemotherapy. Therefore, we aimed to investigate the differences in biological effects between these two ZNF384-r molecules.

METHOD

We transduced BCP-ALL cell lines with both TCF3::ZNF384 and EP300::ZNF384 by retrovirus-mediated gene transduction, and examined the biological effects.

RESULTS

Flow cytometric analysis and RT-qPCR revealed down-regulation of CD10 in BCP-ALL cells after transduction with both TCF3::ZNF384 and EP300::ZNF384. The annexin-V binding apoptosis assay indicated that TCF3::ZNF384-, but not EP300::ZNF384-, expressing cells exhibited increased resistance to dexamethasone-induced apoptosis. By means of an oligonucleotide microarray and RT-qPCR, we observed that the transduction of TCF3::ZNF384, but not EP300::ZNF384, leads to significant enhancement of cyclin D2 (CCND2) gene expression in BCP-ALL cells, but no growth advantage was observed.

CONCLUSION

Our data suggest that the acquisition of dexamethasone resistance in BCP-ALL cell lines is an effect of TCF3::ZNF384 protein distinct from EP300::ZNF384. Other than the common functions of ZNF384-r that contribute to the development of leukemia with a lineage-ambiguous phenotype, TCF3::ZNF384 may exhibit a fusion partner-dependent function distinct from EP300::ZNF384 and participate in the formation of characteristic clinical features of TCF3::ZNF384-expressing ALL patients.

RGS1 and CREB5 are direct and common transcriptional targets of ZNF384-fusion proteins

BACKGROUND

ZNF384-fusion (Z-fusion) genes were recently identified in B-cell acute lymphoblastic leukemia (B-ALL) and are frequent in Japanese adult patients. The frequency is about 20% in those with Philadelphia chromosome-negative B-ALL. ZNF384 is a transcription factor and Z-fusion proteins have increased transcriptional activity; however, the detailed mechanisms of leukemogenesis of Z-fusion proteins have yet to be clarified.

METHODS

We established three transfectants of cell lines expressing different types of Z-fusion proteins, and analyzed their gene expression profile (GEP) by RNA-seq. We also analyzed the GEP of clinical ALL samples using our previous RNA-seq data of 323 Japanese ALL patients. We selected upregulated genes in both Z-fusion gene-expressing transfectants and Z-fusion gene-positive ALL samples, and investigated the binding of Z-fusion proteins to regulatory regions of the candidate genes by ChIP-qPCR.

RESULTS

We selected six commonly upregulated genes. After the investigation by ChIP-qPCR, we finally identified CREB5 and RGS1 as direct and common target genes. RGS1 is an inhibitor of CXCL12-CXCR4 signaling that is required for the homing of hematopoietic progenitor cells to the bone marrow microenvironment and development of B cells. Consistent with this, Z-fusion gene transfectants showed impaired migration toward CXCL12.

CONCLUSIONS

We identified CREB5 and RGS1 as direct and common transcriptional targets of Z-fusion proteins. The present results provide novel insight into the aberrant transcriptional regulation by Z-fusion proteins.

Loss of Nmp4 enhances bone gain from sclerostin antibody administration

Severe osteoporosis is often treated with one of three Food and Drug Administration (FDA)-approved osteoanabolics. These drugs act by (1) parathyroid hormone (PTH) receptor stimulation using analogues to PTH (teriparatide) or PTH-related peptide (abaloparatide) or by (2) monoclonal antibody neutralization of sclerostin, an innate Wnt inhibitor (Scl-mAb, romosozumab-aqqg). The efficacies of both strategies wane over time. The transcription factor Nmp4 (Nuclear Matrix Protein 4) is expressed in all tissues yet mice lacking this gene are healthy and exhibit enhanced PTH-induced bone formation. Conditional deletion of Nmp4 in mesenchymal stem progenitor cells (MSPCs) phenocopies the elevated response to PTH in global Nmp4-/- mice. However, targeted deletion in later osteoblast stages does not replicate this response. In this study we queried whether loss of Nmp4 improves Scl-mAb potency. Experimental cohorts included global Nmp4-/- and Nmp4+/+ littermates and three conditional knockout models. Nmp4-floxed (Nmp4fl/fl) mice were crossed with mice harboring one of three Cre-drivers (i) Prx1Cre+ targeting MSPCs, (ii) BglapCre+ (mature osteocalcin-expressing osteoblasts), and (iii) Dmp1Cre+ (osteocytes). Female mice were treated with Scl-mAb or 0.9 % saline vehicle for 4 or 7 weeks from 10 weeks of age. Skeletal response was assessed using micro-computed tomography, dual-energy X-ray absorptiometry, bone histomorphometry, and serum analysis. Global Nmp4-/- mice exhibited enhanced Scl-mAb-induced increases in trabecular bone in the femur and spine and a heightened increase in whole body areal bone mineral density compared to global Nmp4+/+ controls. This improved Scl-mAb potency was primarily driven by enhanced increases in bone formation. Nmp4fl/fl;PrxCre+ mice showed an exaggerated Scl-mAb-induced increase in femoral bone but not in the spine since Prrx1 is not expressed in vertebra. The Nmp4fl/fl;BglapCre+ and Nmp4fl/fl;Dmp1Cre+ mice did not exhibit an improved Scl-mAb response. We conclude that Nmp4 expression in MSPCs interferes with the bone anabolic response to anti-sclerostin therapy.

NMP4, an Arbiter of Bone Cell Secretory Capacity and Regulator of Skeletal Response to PTH Therapy

The skeleton is a secretory organ, and the goal of some osteoporosis therapies is to maximize bone matrix output. Nmp4 encodes a novel transcription factor that regulates bone cell secretion as part of its functional repertoire. Loss of Nmp4 enhances bone response to osteoanabolic therapy, in part, by increasing the production and delivery of bone matrix. Nmp4 shares traits with scaling factors, which are transcription factors that influence the expression of hundreds of genes to govern proteome allocation for establishing secretory cell infrastructure and capacity. Nmp4 is expressed in all tissues and while global loss of this gene leads to no overt baseline phenotype, deletion of Nmp4 has broad tissue effects in mice challenged with certain stressors. In addition to an enhanced response to osteoporosis therapies, Nmp4-deficient mice are less sensitive to high fat diet-induced weight gain and insulin resistance, exhibit a reduced disease severity in response to influenza A virus (IAV) infection, and resist the development of some forms of rheumatoid arthritis. In this review, we present the current understanding of the mechanisms underlying Nmp4 regulation of the skeletal response to osteoanabolics, and we discuss how this unique gene contributes to the diverse phenotypes among different tissues and stresses. An emerging theme is that Nmp4 is important for the infrastructure and capacity of secretory cells that are critical for health and disease.

Conditional Loss of Nmp4 in Mesenchymal Stem Progenitor Cells Enhances PTH-Induced Bone Formation

Activation of bone anabolic pathways is a fruitful approach for treating severe osteoporosis, yet FDA-approved osteoanabolics, eg, parathyroid hormone (PTH), have limited efficacy. Improving their potency is a promising strategy for maximizing bone anabolic output. Nmp4 (Nuclear Matrix Protein 4) global knockout mice exhibit enhanced PTH-induced increases in trabecular bone but display no overt baseline skeletal phenotype. Nmp4 is expressed in all tissues; therefore, to determine which cell type is responsible for driving the beneficial effects of Nmp4 inhibition, we conditionally removed this gene from cells at distinct stages of osteogenic differentiation. Nmp4-floxed (Nmp4fl/fl ) mice were crossed with mice bearing one of three Cre drivers including (i) Prx1Cre+  to remove Nmp4 from mesenchymal stem/progenitor cells (MSPCs) in long bones; (ii) BglapCre+  targeting mature osteoblasts, and (iii) Dmp1Cre+  to disable Nmp4 in osteocytes. Virgin female Cre+  and Cre- mice (10 weeks of age) were sorted into cohorts by weight and genotype. Mice were administered daily injections of either human PTH 1-34 at 30 μg/kg or vehicle for 4 weeks or 7 weeks. Skeletal response was assessed using dual-energy X-ray absorptiometry, micro-computed tomography, bone histomorphometry, and serum analysis for remodeling markers. Nmp4fl/fl ;Prx1Cre+  mice virtually phenocopied the global Nmp4-/- skeleton in the femur, ie, a mild baseline phenotype but significantly enhanced PTH-induced increase in femur trabecular bone volume/total volume (BV/TV) compared with their Nmp4fl/fl ;Prx1Cre- controls. This was not observed in the spine, where Prrx1 is not expressed. Heightened response to PTH was coincident with enhanced bone formation. Conditional loss of Nmp4 from the mature osteoblasts (Nmp4fl/fl ;BglapCre+ ) failed to increase BV/TV or enhance PTH response. However, conditional disabling of Nmp4 in osteocytes (Nmp4fl/fl ;Dmp1Cre+ ) increased BV/TV without boosting response to hormone under our experimental regimen. We conclude that Nmp4-/- Prx1-expressing MSPCs drive the improved response to PTH therapy and that this gene has stage-specific effects on osteoanabolism. © 2022 American Society for Bone and Mineral Research (ASBMR).

ZNF384 fusion oncoproteins drive lineage aberrancy in acute leukemia

ZNF384-rearranged fusion oncoproteins (FO) define a subset of lineage ambiguous leukemias, but their mechanistic role in leukemogenesis and lineage ambiguity is poorly understood. Using viral expression in mouse and human hematopoietic stem and progenitor cells (HSPCs) and a Ep300::Znf384 knockin mouse model, we show that ZNF384 FO promote hematopoietic expansion, myeloid lineage skewing, and self-renewal. In mouse HSPCs, concomitant lesions, such as NRASG12D, were required for fully penetrant leukemia, whereas in human HSPCs expression of ZNF384 FO drove B/myeloid leukemia, with sensitivity of a ZNF384-rearranged xenograft to FLT3 inhibition in vivo. Mechanistically, ZNF384 FO occupy a subset of predominantly intragenic/enhancer regions with increased histone 3 lysine acetylation and deregulate expression of hematopoietic stem cell transcription factors. These data define a paradigm for FO-driven lineage ambiguous leukemia, in which expression in HSPCs results in deregulation of lineage-specific genes and hematopoietic skewing, progressing to full leukemia in the context of proliferative stress.

Nmp4, a Regulator of Induced Osteoanabolism, Also Influences Insulin Secretion and Sensitivity

A bidirectional and complex relationship exists between bone and glycemia. Persons with type 2 diabetes (T2D) are at risk for bone loss and fracture, however, heightened osteoanabolism may ameliorate T2D-induced deficits in glycemia as bone-forming osteoblasts contribute to energy metabolism via increased glucose uptake and cellular glycolysis. Mice globally lacking nuclear matrix protein 4 (Nmp4), a transcription factor expressed in all tissues and conserved between humans and rodents, are healthy and exhibit enhanced bone formation in response to anabolic osteoporosis therapies. To test whether loss of Nmp4 similarly impacted bone deficits caused by diet-induced obesity, male wild-type and Nmp4-/- mice (8 weeks) were fed either low-fat diet or high-fat diet (HFD) for 12 weeks. Endpoint parameters included bone architecture, structural and estimated tissue-level mechanical properties, body weight/composition, glucose-stimulated insulin secretion, glucose tolerance, insulin tolerance, and metabolic cage analysis. HFD diminished bone architecture and ultimate force and stiffness equally in both genotypes. Unexpectedly, the Nmp4-/- mice exhibited deficits in pancreatic β-cell function and were modestly glucose intolerant under normal diet conditions. Despite the β-cell deficits, the Nmp4-/- mice were less sensitive to HFD-induced weight gain, increases in % fat mass, and decreases in glucose tolerance and insulin sensitivity. We conclude that Nmp4 supports pancreatic β-cell function but suppresses peripheral glucose utilization, perhaps contributing to its suppression of induced skeletal anabolism. Selective disruption of Nmp4 in peripheral tissues may provide a strategy for improving both induced osteoanabolism and energy metabolism in comorbid patients.

ZNF384-fusion proteins have high affinity for the transcriptional coactivator EP300 and aberrant transcriptional activities

Zinc-finger protein 384 (ZNF384) fusion (Z-fusion) genes have recently been identified as recurrent fusion genes in B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) and have been detected in 7-17% of Philadelphia chromosome-negative BCP-ALL cases. We selected SALL4 and ID2 as potential Z-fusion-specific transcriptional targets that might lead to the differentiation disorder of Z-fusion-positive ALL. The introduction of EP300-ZNF384 and SYNRG-ZNF384 induced the expression of these genes. Z-fusion proteins exhibited stronger transcriptional activities on the promoter or enhancer region of these genes than Wild-Z. Furthermore, GST pull-down assay revealed that Z-fusion proteins associated more strongly with EP300 than Wild-Z. Coexpression of EP300 specifically enhanced the transcriptional activities of Z-fusion proteins. We propose the increased EP300 binding of Z-fusion proteins as a mechanism for their increased transcriptional activities.

The role of the protein-RNA recognition code in neurodegeneration

MicroRNAs are small endogenous RNAs that pair and bind to sites on mRNAs to direct post-transcriptional repression. However, there is a possibility that microRNAs directly influence protein structure and activity, and this influence can be termed post-translational riboregulation. This conceptual review explores the literature on neurodegenerative disorders. Research on the association between neurodegeneration and RNA-repeat toxicity provides data that support a protein-RNA recognition code. For example, this code explains why hnRNP H and SFPQ proteins, which are involved in amyotrophic lateral sclerosis, are sequestered by the (GGGGCC)n repeat sequence. Similarly, it explains why MNBL proteins and (CTG)n repeats in RNA, which are involved in myotonic dystrophy, are sequestered into RNA foci. Using this code, proteins involved in diseases can be identified. A simple protein BLAST search of the human genome for amino acid repeats that correspond to the nucleotide repeats reveals new proteins among already known proteins that are involved in diseases. For example, the (CAG)n repeat sequence, when transcribed into possible peptide sequences, leads to the identification of PTCD3, Rem2, MESP2, SYPL2, WDR33, COL23A1, and others. After confirming this approach on RNA repeats, in the next step, the code was used in the opposite manner. Proteins that are involved in diseases were compared with microRNAs involved in those diseases. For example, a reasonable correspondence of microRNA 9 and 107 with amyloid-β-peptide (Aβ42) was identified. In the last step, a miRBase search for micro-nucleotides, obtained by transcription of a prion amino acid sequence, revealed new microRNAs and microRNAs that have previously been identified as involved in prion diseases. This concept provides a useful key for designing RNA or peptide probes.

EP300-ZNF384 fusion gene product up-regulates GATA3 gene expression and induces hematopoietic stem cell gene expression signature in B-cell precursor acute lymphoblastic leukemia cells

ZNF384-related fusion genes are associated with a distinct subgroup of B-cell precursor acute lymphoblastic leukemias in childhood, with a frequency of approximately 3-4%. We previously identified a novel EP300-ZNF384 fusion gene. Patients with the ZNF384-related fusion gene exhibit a hematopoietic stem cell (HSC) gene expression signature and characteristic immunophenotype with negative or low expression of CD10 and aberrant expression of myeloid antigens, such as CD33 and CD13. However, the molecular basis of this pathogenesis remains completely unknown. In the present study, we examined the biological effects of EP300-ZNF384 expression induced by retrovirus-mediated gene transduction in an REH B-cell precursor acute lymphoblastic leukemia cell line, and observed the acquisition of the HSC gene expression signature and an up-regulation of GATA3 gene expression, as assessed by microarray analysis. In contrast, the gene expression profile induced by wild-type ZNF384 in REH cells was significantly different from that by EP300-ZNF384 expression. Together with the results of reporter assays, which revealed the enhancement of GATA3-promoter activity by EP300-ZNF384 expression, these findings suggest that EP300-ZNF384 mediates GATA3 gene expression and may be involved in the acquisition of the HSC gene expression signature and characteristic immunophenotype in B-cell precursor acute lymphoblastic leukemia cells.

Multi-strategy genome-wide association studies identify the DCAF16-NCAPG region as a susceptibility locus for average daily gain in cattle

Average daily gain (ADG) is the most economically important trait in beef cattle industry. Using genome-wide association study (GWAS) approaches, previous studies have identified several causal variants within the PLAG1, NCAPG and LCORL genes for ADG in cattle. Multi-strategy GWASs were implemented in this study to improve detection and to explore the causal genes and regions. In this study, we conducted GWASs based on the genotypes of 1,173 Simmental cattle. In the SNP-based GWAS, the most significant SNPs (rs109303784 and rs110058857, P = 1.78 × 10⁻⁷) were identified in the NCAPG intron on BTA6 and explained 4.01% of the phenotypic variance, and the independent and significant SNP (rs110406669, P = 5.18 × 10⁻⁶) explained 3.32% of the phenotypic variance. Similarly, in the haplotype-based GWAS, the most significant haplotype block, Hap-6-N1416 (P = 2.56 × 10⁻⁸), spanned 12.7 kb on BTA6 and explained 4.85% of the phenotypic variance. Also, in the gene-based GWAS, seven significant genes were obtained which included DCAF16 and NCAPG. Moreover, analysis of the transcript levels confirmed that transcripts abundance of NCAPG (P = 0.046) and DCAF16 (P = 0.046) were significantly correlated with the ADG trait. Overall, our results from the multi-strategy GWASs revealed the DCAF16-NCAPG region to be a susceptibility locus for ADG in cattle.

Novel action of FOXL2 as mediator of Col1a2 gene autoregulation

FOXL2 belongs to the evolutionarily conserved forkhead box (FOX) superfamily and is a master transcription factor in a spectrum of developmental pathways, including ovarian and eyelid development and bone, cartilage and uterine maturation. To analyse its action, we searched for proteins that interact with FOXL2. We found that FOXL2 interacts with specific C-terminal propeptides of several fibrillary collagens. Because these propeptides can participate in feedback regulation of collagen biosynthesis, we inferred that FOXL2 could thereby affect the transcription of the cognate collagen genes. Focusing on COL1A2, we found that FOXL2 indeed affects collagen synthesis, by binding to a DNA response element located about 65Kb upstream of this gene. According to our hypothesis we found that in Foxl2(-/-) mouse ovaries, Col1a2 was elevated from birth to adulthood. The extracellular matrix (ECM) compartmentalizes the ovary during folliculogenesis, (with type I, type III and type IV collagens as primary components), and ECM composition changes during the reproductive lifespan. In Foxl2(-/-) mouse ovaries, in addition to up-regulation of Col1a2, Col3a1, Col4a1 and fibronectin were also upregulated, while laminin expression was reduced. Thus, by regulating levels of extracellular matrix components, FOXL2 may contribute to both ovarian histogenesis and the fibrosis attendant on depletion of the follicle reserve during reproductive aging and menopause.

Nuclear Matrix Protein 4 Is a Novel Regulator of Ribosome Biogenesis and Controls the Unfolded Protein Response via Repression of Gadd34 Expression

The unfolded protein response (UPR) maintains protein homeostasis by governing the processing capacity of the endoplasmic reticulum (ER) to manage ER client loads; however, key regulators within the UPR remain to be identified. Activation of the UPR sensor PERK (EIFAK3/PEK) results in the phosphorylation of the α subunit of eIF2 (eIF2α-P), which represses translation initiation and reduces influx of newly synthesized proteins into the overloaded ER. As part of this adaptive response, eIF2α-P also induces a feedback mechanism through enhanced transcriptional and translational expression of Gadd34 (Ppp1r15A),which targets type 1 protein phosphatase for dephosphorylation of eIF2α-P to restore protein synthesis. Here we describe a novel mechanism by which Gadd34 expression is regulated through the activity of the zinc finger transcription factor NMP4 (ZNF384, CIZ). NMP4 functions to suppress bone anabolism, and we suggest that this occurs due to decreased protein synthesis of factors involved in bone formation through NMP4-mediated dampening of Gadd34 and c-Myc expression. Loss of Nmp4 resulted in an increase in c-Myc and Gadd34 expression that facilitated enhanced ribosome biogenesis and global protein synthesis. Importantly, protein synthesis was sustained during pharmacological induction of the UPR through a mechanism suggested to involve GADD34-mediated dephosphorylation of eIF2α-P. Sustained protein synthesis sensitized cells to pharmacological induction of the UPR, and the observed decrease in cell viability was restored upon inhibition of GADD34 activity. We conclude that NMP4 is a key regulator of ribosome biogenesis and the UPR, which together play a central role in determining cell viability during endoplasmic reticulum stress.

Mice Deficient in CIZ/NMP4 Develop an Attenuated Form of K/BxN-Serum Induced Arthritis

CIZ/NMP4 (Cas interacting zinc finger protein, Nmp4, Zfp384) is a transcription factor that is known to regulate matrix related-proteins. To explore the possible pathophysiological role of CIZ/NMP4 in arthritis, we examined CIZ/NMP4 expression in articular cartilage in arthritis model. CIZ/NMP4 was expressed in the articular chondrocytes of mice at low levels while its expression was enhanced when arthritis was induced. Arthritis induction increased clinical score in wild type mice. In contrast, CIZ/NMP4 deficiency suppressed such rise in the levels of arthritis score and swelling of soft tissue. CIZ/NMP4 deficiency also reduced invasion of inflammatory cells in joint tissue. Quantitative PCR analyses of mRNA from joints revealed that arthritis-induced increase in expressions of IL-1β was suppressed by CIZ/NMP4 deficiency. CIZ/NMP4 bound to IL-1β promoter and activated its transcription. The increase in CIZ/NMP4 in arthritis was also associated with enhancement in bone resorption and cartilage matrix degradation. In fact, RANKL, a signaling molecule prerequisite for osteoclastogenesis and, MMP-3, a clinical marker for arthritis were increased in joints upon arthritis induction. In contrast, CIZ/NMP4 deficiency suppressed the arthritis-induced increase in bone resorption, expression of RANKL and MMP-3 mRNA. Thus, CIZ/NMP4 plays a role in the development of arthritis at least in part through regulation of key molecules related to the arthritis.

Genome-Wide Mapping and Interrogation of the Nmp4 Antianabolic Bone Axis

PTH is an osteoanabolic for treating osteoporosis but its potency wanes. Disabling the transcription factor nuclear matrix protein 4 (Nmp4) in healthy, ovary-intact mice enhances bone response to PTH and bone morphogenetic protein 2 and protects from unloading-induced osteopenia. These Nmp4(-/-) mice exhibit expanded bone marrow populations of osteoprogenitors and supporting CD8(+) T cells. To determine whether the Nmp4(-/-) phenotype persists in an osteoporosis model we compared PTH response in ovariectomized (ovx) wild-type (WT) and Nmp4(-/-) mice. To identify potential Nmp4 target genes, we performed bioinformatic/pathway profiling on Nmp4 chromatin immunoprecipitation sequencing (ChIP-seq) data. Mice (12 w) were ovx or sham operated 4 weeks before the initiation of PTH therapy. Skeletal phenotype analysis included microcomputed tomography, histomorphometry, serum profiles, fluorescence-activated cell sorting and the growth/mineralization of cultured WT and Nmp4(-/-) bone marrow mesenchymal stem progenitor cells (MSPCs). ChIP-seq data were derived using MC3T3-E1 preosteoblasts, murine embryonic stem cells, and 2 blood cell lines. Ovx Nmp4(-/-) mice exhibited an improved response to PTH coupled with elevated numbers of osteoprogenitors and CD8(+) T cells, but were not protected from ovx-induced bone loss. Cultured Nmp4(-/-) MSPCs displayed enhanced proliferation and accelerated mineralization. ChIP-seq/gene ontology analyses identified target genes likely under Nmp4 control as enriched for negative regulators of biosynthetic processes. Interrogation of mRNA transcripts in nondifferentiating and osteogenic differentiating WT and Nmp4(-/-) MSPCs was performed on 90 Nmp4 target genes and differentiation markers. These data suggest that Nmp4 suppresses bone anabolism, in part, by regulating IGF-binding protein expression. Changes in Nmp4 status may lead to improvements in osteoprogenitor response to therapeutic cues.

Lipopolysaccharide (LPS) induces the apoptosis and inhibits osteoblast differentiation through JNK pathway in MC3T3-E1 cells

Bone degradation is a serious complication of chronic inflammatory diseases such as septic arthritis, osteomyelitis, and infected orthopedic implant failure. Up to date, effective therapeutic treatments for bacteria-caused bone destruction are limited. In our previous study, we found that LPS promoted osteoclast differentiation and activity through activation of mitogen-activated protein kinases (MAPKs) pathway such as c-Jun N-terminal kinases (JNK) and extracellular signal regulated kinase (ERK1/2). The current study was to evaluate the mechanism of LPS on the apoptosis and osteoblast differentiation in MC3T3-E1 cells. MC3T3-E1 osteoblasts were non-treated, treated with LPS. After treatment, the cell viability, the activity of alkaline phosphatase (ALP) and caspase-3 were measured. The expressions of osteoblast-specific genes and Bax, Bcl-2, and caspase-3 were determined by real-time quantitative polymerase chain reaction (qPCR). Protein levels of Bax, Bcl-2, caspase-3, and phosphorylation of MAPKs were measured using Western blotting assays. The MAPK signaling pathway was blocked by pretreatment with JNK inhibitor SP600125. LPS treatment induced a significant decrease in cell metabolism, viability, and ALP activity in MC3T3-E1 cells. LPS also significantly decreased mRNA expressions of osteoblast-related genes in MC3T3-E1 cells. On the other hand, LPS significantly upregulated mRNA expressions and protein levels of Bax and caspase-3 as well as activation of caspase-3, whereas decreased Bcl-2 expression in MC3T3-E1 cells. Furthermore, LPS significantly promoted MAPK pathway including the phosphorylation of JNK and the phosphorylation of ERK1/2; moreover, pretreatment with JNK inhibitor not only attenuated both of phosphorylation-JNK and ERK1/2 enhanced by LPS in MC3T3-E1 cells, but also reversed the downregulated expressions of osteoblast-specific genes including ALP and BSP induced by LPS. In conclusion, LPS could induce osteoblast apoptosis and inhibit osteoblast differentiation via activation of JNK pathway.

Quercetin reversed lipopolysaccharide-induced inhibition of osteoblast differentiation through the mitogen‑activated protein kinase pathway in MC3T3-E1 cells

Quercetin, a flavonoid found in onions and other vegetables, has potential inhibitory effects on bone resorption in vivo and in vitro. In our previous study it was identified that quercetin triggered the apoptosis of lipopolysaccharide (LPS)‑induced osteoclasts and inhibited bone resorption. Currently, little information is available detailing the effect of quercetin on osteoblast differentiation and bone formation in bacteria‑induced inflammatory diseases. The present study aimed to investigate the effect of quercetin on osteoblast differentiation in MC3T3‑E1 osteoblasts stimulated with LPS. LPS significantly downregulated the mRNA expression of osteoblast‑related genes in the MC3T3‑E1 cells. By contrast, quercetin significantly restored the LPS‑suppressed mRNA expression of osteoblast‑related genes in a dose‑dependent manner. Quercetin also restored the protein expression of Osterix in MC3T3‑E1 cells suppressed by LPS. Furthermore, quercetin selectively triggered the activation of the mitogen‑activated protein kinase (MAPK) pathway by enhancing the expression of extracellular signal-regulated kinase and reducing the expression of c‑Jun N‑terminal kinase. These data suggest that quercetin reversed the inhibition of osteoblast differentiation induced by LPS through MAPK signaling. These findings suggest that quercetin may be of potential use as a therapeutic agent to restore osteoblast function in bacteria‑induced bone diseases.

Functional impairment of bone formation in the pathogenesis of osteoporosis: the bone marrow regenerative competence

The skeleton is a high-renewal organ that undergoes ongoing cycles of remodeling. The regenerative bone formation arm ultimately declines in the aging, postmenopausal skeleton, but current therapies do not adequately address this deficit. Bone marrow is the primary source of the skeletal anabolic response and the mesenchymal stem cells (MSCs), which give rise to bone matrix-producing osteoblasts. The identity of these stem cells is emerging, but it now appears that the term 'MSC' has often been misapplied to the bone marrow stromal cell (BMSC), a progeny of the MSC. Nevertheless, the changes in BMSC phenotype associated with age and estrogen depletion likely contribute to the attenuated regenerative competence of the marrow and may reflect alterations in MSC phenotype. Here we summarize current concepts in bone marrow MSC identity, and within this context, review recent observations on changes in bone marrow population dynamics associated with aging and menopause.

Nmp4/CIZ closes the parathyroid hormone anabolic window

Chronic degenerative diseases are increasing with the aging U.S. population. One consequence of this phenomenon is the need for long-term osteoporosis therapies. Parathyroid hormone (PTH), the only FDA-approved treatment that adds bone to the aged skeleton, loses its potency within two years of initial treatment but the mechanism regulating its limited "anabolic window" is unknown. We have discovered that disabling the nucleocytoplasmic shuttling transcription factor nuclear matrix protein 4/cas interacting zinc finger protein (Nmp4/CIZ) in mice extends the PTH bone-forming capacity. Nmp4 was discovered during our search for nuclear matrix transcription factors that couple this hormone's impact on osteoblast cytoskeletal and nuclear organization with its anabolic capacity. CIZ was independently discovered as a protein that associates with the focal adhesion-associated mechanosensor p130Cas. The Nmp4/CIZ-knockout (KO) skeletal phenotype exhibits a modestly enhanced bone mineral density but manifests an exaggerated response to both PTH and to BMP2 and is resistant to disuse-induced bone loss. The cellular basis of the global Nmp4/CIZ-KO skeletal phenotype remains to be elucidated but may involve an expansion of the bone marrow osteoprogenitor population along with modestly enhanced osteoblast and osteoclast activities supporting anabolic bone turnover. As a shuttling Cys(2)His(2) zinc finger protein, Nmp4/CIZ acts as a repressive transcription factor perhaps associated with epigenetic remodeling complexes, but the functional significance of its interaction with p130Cas is not known. Despite numerous remaining questions, Nmp4/CIZ provides insights into how the anabolic window is regulated, and itself may provide an adjuvant therapy target for the treatment of osteoporosis by extending PTH anabolic efficacy.

Nmp4/CIZ suppresses the parathyroid hormone anabolic window by restricting mesenchymal stem cell and osteoprogenitor frequency

Parathyroid hormone (PTH) anabolic osteoporosis therapy is intrinsically limited by unknown mechanisms. We previously showed that disabling the transcription factor Nmp4/CIZ in mice expanded this anabolic window while modestly elevating bone resorption. This enhanced bone formation requires a lag period to materialize. Wild-type (WT) and Nmp4-knockout (KO) mice exhibited equivalent PTH-induced increases in bone at 2 weeks of treatment, but by 7 weeks, the null mice showed more new bone. At 3-week treatment, serum osteocalcin, a bone formation marker, peaked in WT mice, but continued to increase in null mice. To determine if 3 weeks is the time when the addition of new bone diverges and to investigate its cellular basis, we treated 10-week-old null and WT animals with human PTH (1-34) (30 μg/kg/day) or vehicle before analyzing femoral trabecular architecture and bone marrow (BM) and peripheral blood phenotypic cell profiles. PTH-treated Nmp4-KO mice gained over 2-fold more femoral trabecular bone than WT by 3 weeks. There was no difference between genotypes in BM cellularity or profiles of several blood elements. However, the KO mice exhibited a significant elevation in CFU-F cells, CFU-F(Alk)(Phos+) cells (osteoprogenitors), and a higher percentage of CFU-F(Alk)(Phos+) cells/CFU-F cells consistent with an increase in CD45-/CD146+/CD105+/nestin+ mesenchymal stem cell frequency. Null BM exhibited a 2-fold enhancement in CD8+ T cells known to support osteoprogenitor differentiation and a 1.6-fold increase in CFU-GM colonies (osteoclast progenitors). We propose that Nmp4/CIZ limits the PTH anabolic window by restricting the number of BM stem, progenitor, and blood cells that support anabolic bone remodeling.

Prenatal antiepileptic exposure associates with neonatal DNA methylation differences

Antiepileptic drugs (AEDs) are used to treat a variety of neuropsychiatric illnesses commonly encountered in women during their reproductive years, including epilepsy and bipolar disorder. Despite their widespread use, the impact of prenatal exposure on fetal development remains obscure. To evaluate whether AEDs taken by pregnant mothers influence DNA methylation patterns in their neonates, DNA was extracted from the umbilical cord blood of 201 neonates whose mothers were treated for neuropsychiatric illness during pregnancy and interrogated across 27,578 CpG sites using the Illumina HumanMethylation27 BeadChip. The association of each methylation value with the cumulative duration of prenatal AED exposure was examined using a linear mixed model. The average methylation level across all CpG sites was calculated for each subject, and this global methylation measure was evaluated similarly. Neonates with a longer duration of AED exposure in pregnancy showed a decrease in average global methylation (p = 0.0045). Further, DNA methylation of CpG sites in 14 genes significantly decreased with the duration of prenatal AED exposure even after adjusting for multiple comparisons (FDR < 0.05). For a small subset (n = 19) of these neonates, a second tissue, placenta, was available in addition to cord blood. Methylation of 3 of these 14 CpG sites was also significantly decreased in placental tissue. These novel data suggest decreased DNA methylation in neonates of mothers who took AEDs during pregnancy. The long-term stability and potential impact of these changes warrant further attention, and caution may be warranted before prescribing AEDs to pregnant women.

Nmp4/CIZ suppresses the response of bone to anabolic parathyroid hormone by regulating both osteoblasts and osteoclasts

How parathyroid hormone (PTH) increases bone mass is unclear, but understanding this phenomenon is significant to the improvement of osteoporosis therapy. Nmp4/CIZ is a nucleocytoplasmic shuttling transcriptional repressor that suppresses PTH-induced osteoblast gene expression and hormone-stimulated gains in murine femoral trabecular bone. To further characterize Nmp4/CIZ suppression of hormone-mediated bone growth, we treated 10-week-old Nmp4-knockout (KO) and wild-type (WT) mice with intermittent human PTH(1-34) at 30 μg/kg daily or vehicle, 7 days/week, for 2, 3, or 7 weeks. Null mice treated with hormone (7 weeks) gained more vertebral and tibial cancellous bone than WT animals, paralleling the exaggerated response in the femur. Interestingly, Nmp4/CIZ suppression of this hormone-stimulated bone formation was not apparent during the first 2 weeks of treatment. Consistent with the null mice enhanced PTH-stimulated addition of trabecular bone, these animals exhibited an augmented hormone-induced increase in serum osteocalcin 3 weeks into treatment. Unexpectedly, the Nmp4-KO mice displayed an osteoclast phenotype. Serum C-terminal telopeptide, a marker for bone resorption, was elevated in the null mice, irrespective of treatment. Nmp4-KO bone marrow cultures produced more osteoclasts, which exhibited elevated resorbing activity, compared to WT cultures. The expression of several genes critical to the development of both osteoblasts and osteoclasts was elevated in Nmp4-KO mice at 2 weeks, but not 3 weeks, of hormone exposure. We propose that Nmp4/CIZ dampens PTH-induced improvement of trabecular bone throughout the skeleton by transiently suppressing hormone-stimulated increases in the expression of proteins key to the required enhanced activity and number of both osteoblasts and osteoclasts.

Mechanosomes carry a loaded message

Understanding the molecular mechanisms that mediate the response of cells to mechanical stimuli, the process known as mechanotransduction, has emerged as a research topic with relevance to human health and disease. Mechanotransduction in bone is particularly relevant because the mammalian skeleton remodels to adapt to its loading environment The mechanosome hypothesis has been proposed to explain how mechanical signals detected at the bone cell membrane are converted into changes in transcription of target genes. In one model, adhesion complexes at the surface of the sensor cell activate multiprotein complexes (mechanosomes) that include both proteins involved in adhesion and transcription factors that move to the nucleus and regulate transcriptional activity of target genes. New work has identified a previously unknown mechanotransduction complex-consisting of nitric oxide (NO), cyclic guanosine monophosphate (cGMP), protein kinase G II, SHP-1, and SHP-2-that associates with β₃ integrins through Src. This complex regulates gene expression in response to fluid flow and has several of the necessary elements of a mechanosome complex. These findings beg the question of just how extensive the mechanosome network is and how mechanosomes interact with other signal transduction pathways that also respond to mechanical load.

The Load-Bearing Mechanosome Revisited

We introduced the mechanosome hypothesis in 2003 as a heuristic model for investigating mechanotransduction in bone (Pavalko et al., J Cell Biochem, 2003, 88(1):104-112). This model suggested specific approaches for investigating how mechanical information is conveyed from the membrane of the sensor bone cell to the target genes and how this transmitted information from the membrane is converted into changes in transcription. The key concepts underlying the mechanosome hypothesis are that load-induced deformation of bone deforms the sensor cell membrane; embedded in the membrane are the focal adhesion and cadherin-catenin complexes, which in turn are physically connected to the chromatin via a solid-state scaffold. The physical stimulation of the membrane launches multiprotein complexes (mechanosomes) from the adhesion platforms while concomitantly tugging target genes into position for contact with the incoming mechanosomes, the carriers of the mechanical information to the nucleus. The mechanosome is comprised of an adhesion-associated protein and a nucleocytoplasmic shuttling transcription factor. Upon arrival at the target gene, mechanosomes alter DNA conformation and thus influence the interactions between trans-acting proteins along the gene, changing gene activity. Here, we update significant progress related to the mechanosome concept since publication of our original hypothesis. The launching of adhesion- and cytoskeletal-associated proteins into the nucleus toward target genes appears to be a common mechanism for regulating cell response to changes in its mechanical microenvironment.

Co-expression of FBN1 with mesenchyme-specific genes in mouse cell lines: implications for phenotypic variability in Marfan syndrome

Mutations in the human FBN1 gene cause Marfan syndrome, a complex disease affecting connective tissues but with a highly variable phenotype. To identify genes that might participate in epistatic interactions with FBN1, and could therefore explain the observed phenotypic variability, we have looked for genes that are co-expressed with Fbn1 in the mouse. Microarray expression data derived from a range of primary mouse cells and cell lines were analysed using the network analysis tool BioLayout Express(3D). A cluster of 205 genes, including Fbn1, were selectively expressed by mouse cell lines of different mesenchymal lineages and by mouse primary mesenchymal cells (preadipocytes, myoblasts, fibroblasts, osteoblasts). Promoter analysis of this gene set identified several candidate transcriptional regulators. Genes within this co-expressed cluster are candidate genetic modifiers for Marfan syndrome and for other connective tissue diseases.

Nmp4/CIZ inhibits mechanically induced beta-catenin signaling activity in osteoblasts

Cellular mechanotransduction, the process of converting mechanical signals into biochemical responses within cells, is a critical aspect of bone health. While the effects of mechanical loading on bone are well recognized, elucidating the specific molecular pathways involved in the processing of mechanical signals by bone cells represents a challenge and an opportunity to identify therapeutic strategies to combat bone loss. In this study we have for the first time examined the relationship between the nucleocytoplasmic shuttling transcription factor nuclear matrix protein-4/cas interacting zinc finger protein (Nmp4/CIZ) and beta-catenin signaling in response to a physiologic mechanical stimulation (oscillatory fluid shear stress, OFSS) in osteoblasts. Using calvaria-derived osteoblasts from Nmp4-deficient and wild-type mice, we found that the normal translocation of beta-catenin to the nucleus in osteoblasts that is induced by OFSS is enhanced when Nmp4/CIZ is absent. Furthermore, we found that other aspects of OFSS-induced mechanotransduction generally associated with the beta-catenin signaling pathway, including ERK, Akt, and GSK3beta activity, as well as expression of the beta-catenin-responsive protein cyclin D1 are also enhanced in cells lacking Nmp4/CIZ. Finally, we found that in the absence of Nmp4/CIZ, OFSS-induced cytoskeletal reorganization and the formation of focal adhesions between osteoblasts and the extracellular substrate is qualitatively enhanced, suggesting that Nmp4/CIZ may reduce the sensitivity of bone cells to mechanical stimuli. Together these results provide experimental support for the concept that Nmp4/CIZ plays an inhibitory role in the response of bone cells to mechanical stimulation induced by OFSS.

Nmp4/CIZ: road block at the intersection of PTH and load

Teriparatide (parathyroid hormone, [PTH]) is the only FDA-approved drug that replaces bone lost to osteoporosis. Enhancing PTH efficacy will improve cost-effectiveness and ameliorate contraindications. Combining this hormone with load-bearing exercise may enhance therapeutic potential consistent with a growing body of evidence that these agonists are synergistic and share common signaling pathways. Additionally, neutralizing molecules that naturally suppress the anabolic response to PTH may also improve the efficacy of treatment with this hormone. Nmp4/CIZ (nuclear matrix protein 4/cas interacting zinc finger)-null mice have enhanced responses to intermittent PTH with respect to increasing trabecular bone mass and are also immune to disuse-induced bone loss likely by the removal of Nmp4/CIZ suppressive action on osteoblast function. Nmp4/CIZ activity may be sensitive to changes in the mechanical environment of the bone cell brought about by hormone- or mechanical load-induced changes in cell shape and adhesion. Nmp4 was identified in a screen for PTH-responsive nuclear matrix architectural transcription factors (ATFs) that we proposed translate hormone-induced changes in cell shape and adhesion into changes in target gene DNA conformation. CIZ was independently identified as a nucleocytoplasmic shuttling transcription factor associating with the mechano-sensitive focal adhesion proteins p130Cas and zxyin. The p130Cas/zyxin/Nmp4/CIZ pathway resembles the beta-catenin/TCF/LEF1 mechanotransduction response limb and both share features with the HMGB1 (high mobility group box 1)/RAGE (receptor for advanced glycation end products) signaling axis. Here we describe Nmp4/CIZ within the context of the PTH-induced anabolic response and consider the place of this molecule in the hierarchy of the PTH-load response network.

Promoter and intron 1 polymorphisms of COL1A1 interact to regulate transcription and susceptibility to osteoporosis

Three polymorphisms (-1997G/T; -1663IndelT and +1245G/T) have been identified in the 5' flank of COL1A1 gene that are associated with osteoporosis but the underlying mechanism is unclear. Here we investigated the functional effects of these variants on COL1A1 transcription. Transcription was 2-fold higher with the osteoporosis-associated G-del-T haplotype compared with the common G-Ins-G haplotype. Gel shift assays showed that the region surrounding the -1663IndelT polymorphism recognized a complex of proteins essential for osteoblast differentiation and function including Nmp4 and Osterix, and the osteoporosis-associated -1663delT allele had increased binding affinity for this complex. Chromatin immunoprecipitation assays confirmed that the region flanking -1663insdelT bound a complex of proteins including Osterix and Nmp4 and also showed evidence of recruitment of Nmp4 to the Sp1 binding site in intron 1. Further studies showed that haplotype G-del-T had higher binding affinity for RNA polymerase II, consistent with increased transcription of the G-del-T allele and there was a significant inverse association between carriage of G-del-T and bone mineral density (BMD) in a cohort of 3270 Caucasian women. We conclude that common polymorphic variants in the 5' flank of COLIA1 regulate transcription by affecting DNA-protein interactions and that increased levels of transcription correlate with reduced BMD values in vivo. This is consistent with a model whereby increased COL1A1 transcription predisposes to osteoporosis, probably by increasing production of the alpha 1 chain and disrupting the normal ratio of collagen type 1 alpha 1 and alpha 2 chains.

Nmp4/CIZ suppresses parathyroid hormone-induced increases in trabecular bone

The nucleocytoplasmic shuttling transcription factor Nmp4/CIZ (nuclear matrix protein 4/cas interacting zinc finger protein) is a ubiquitously expressed protein that regulates both cytoplasmic and nuclear activities. In the nucleus, Nmp4/CIZ represses transcription of genes crucial to osteoblast differentiation and genes activated by various anabolic stimuli, including parathyroid hormone (PTH). We investigated the role of Nmp4/CIZ in the PTH-induced increase in bone by engineering mice with loss-of-function mutations in the Nmp4/CIZ gene, and treating 10-week-old female mice with anabolic doses of human PTH (1-34) at 30 microg/kg/day, 7 day/week, for 7 weeks or vehicle control. The untreated, baseline phenotype of the Nmp4-null mice between 8 and 16 weeks of age included a modest but significant increase in bone mineral density (BMD) and bone mineral content (BMC) compared to wild-type (WT) mice. Type I collagen mRNA expression was moderately elevated in the femurs of the Nmp4-null mice. The Nmp4 mutant alleles decreased body weight by 4% when expressed on a mixed background but the same alleles on a pure B6 background yielded a significant, 15% increase in body weight among the KO mice, compared to their WT controls. Hormone treatment equally enhanced BMD and BMC over vehicle-treated mice in both the WT and Nmp4-null groups but Nmp4-KO mice exhibited a significantly greater PTH-induced acquisition of femoral trabecular bone as compared to WT mice. These data support our hypothesis that Nmp4/CIZ is a transcriptional attenuator that suppresses osteoid synthesis and PTH-mediated acquisition of cancellous bone. J. Cell. Physiol. 219: 734-743, 2009. (c) 2009 Wiley-Liss, Inc.

E2A-ZNF384 and NOL1-E2A fusion created by a cryptic t(12;19)(p13.3; p13.3) in acute leukemia

A 5-year-old boy who initially presented with ALL and relapsed 4 months later with AML was found to have an add(19) in the leukemia cells. FISH revealed that the add(19) was really a cryptic t(l2;l9)(p13.3;p13.3) interrupting E2A (TCF3). Nucleotide sequences of cloned genomic fragments with the E2A rearrangements revealed that the der(12) contained E2A joined to an intron of the NOLI (p120) gene. Reverse transcriptase (RT)-PCR of patient lymphoblast RNA showed expression of in-frame fusion cDNAs consisting of most of NOL1 fused to the 3' portion of E2A that encoded part of the second transcriptional activation domain and the DNA binding and protein dimerization motifs. The reciprocal der(19) E2A genomic rearrangements included 5' regions of E2A joined to an intron of the ZNF384 (NMP4, CIZ) gene, located approximately 450 kb centromeric to NOL1 on chromosome 12. RT-PCR showed expression of in-frame E2A-ZNF384 fusion cDNAs. To our knowledge, this is the second report of a chromosome translocation in leukemia resulting in two different gene fusions. This is the first report of expression of E2A fusion protein that includes the DNA binding and protein dimerization domains due to a more proximal break in E2A compared to those described previously.

Single-nucleotide polymorphisms in the COL1A1 regulatory regions are associated with otosclerosis

Otosclerosis (MIM 166800) has a prevalence of 0.2-1% among white adults, making it the single most common cause of hearing impairment in this ethnic group. Although measles virus, hormones, human leukocyte antigen alleles and genetic factors have been implicated in the development of otosclerosis, its etiology remains unknown. In a focused effort to identify genetic factors in otosclerosis, we have mapped four disease loci (MIM 166800/605727/608244/608787); however, cloning the disease-causing genes in these intervals has not been successful. Here, we used a case-control study design to investigate the association between collagen type I genes and otosclerosis. We identified susceptibility and protective haplotypes in COL1A1 that are significantly associated with otosclerosis in the Caucasian population. These haplotypes alter reporter gene activity in an osteoblast cell line by affecting binding of transcription factors to cis-acting elements. Our data suggest that increased amounts of collagen alpha1(I) homotrimers are causally related to the development of otosclerosis. Consistent with this hypothesis, mouse mutants homozygous for a Col1a2 frameshift mutation on a C57BL/6J background that deposit only homotrimeric type I collagen have hearing loss.

Deficiency of CIZ, a nucleocytoplasmic shuttling protein, prevents unloading-induced bone loss through the enhancement of osteoblastic bone formation in vivo

Disuse osteoporosis is a major cause to increase the risk of fractures in bed-ridden patients whose numbers are increasing in our modern society. However, the mechanisms underlying the sensing of mechanical stress in bone are largely unknown. CIZ localizes at cell adhesion plaque and transfers into nuclear compartments and activates promoters of the genes encoding enzymes, which degrade matrix proteins to link signals from the cell adhesion site to nuclear events. We examined whether this nucleocytoplasmic shuttling protein would be involved in mediation of mechanical stress signaling. Unloading based on tail suspension reduced bone volume in wild-type mice. In contrast, CIZ-deficient mice revealed suppression in such reduction of bone mass due to unloading. Histomorphometric analysis revealed that unloading suppressed the levels of osteoblastic bone formation parameters, and such suppression of bone formation parameters was blocked by CIZ-deficiency. Osteoclastic bone resorption parameters were similar regardless of CIZ-deficiency after 2-week unloading. Mineralized nodule formation in the cultures of bone marrow cells obtained from the bone of mice subjected to unloading was suppressed in wild-type mice. CIZ deficiency blocked such reduction in nodule formation induced by unloading. These data indicated that nucleocytoplasmic shuttling protein, CIZ, plays a pivotal role in the response of bone mass in unloading condition.

Identification in human osteoarthritic chondrocytes of proteins binding to the novel regulatory site AGRE in the human matrix metalloprotease 13 proximal promoter

OBJECTIVE

Matrix metalloprotease 13 (MMP-13) plays a major role in osteoarthritic (OA) processes. We previously identified the AG-rich element (AGRE) regulatory site (GAAAAGAAAAAG) in the proximal promoter of this gene. Electrophoretic mobility shift assays (EMSAs) done with nuclear extracts from OA chondrocytes showed the presence of 2 AGRE protein-binding complexes, the formation of which depended on the pathophysiologic state (high or low) of the cells; the low OA (L-OA) chondrocytes have low MMP-13 basal levels and high interleukin-1beta (IL-1beta) inducibility, and the high OA (H-OA) chondrocytes have high MMP-13 basal levels and low IL-1beta inducibility. In this study, we sought to determine the importance of individual AGRE bases in promoter activity and to identify AGRE binding proteins from L-OA and H-OA chondrocyte complexes.

METHODS

Promoter activity was determined following transient transfection into human OA chondrocytes. AGRE binding proteins were identified by mass spectroscopy.

RESULTS

Individual mutations of the AGRE site differentially modulated promoter activity, indicating that the intact AGRE site is required for optimal MMP-13 expression. Damage-specific DNA binding protein 1 (DDB-1) was identified in the L-OA chondrocyte-binding complex. EMSA experiments performed with the mutation of the left AGRE site (GTGCTGAAAAAG) and nuclear extracts of L-OA chondrocytes reproduced the pattern seen in the H-OA chondrocytes. Mass spectroscopy identified p130cas as one of the proteins in this complex. Supershift experiments showed the presence of p130cas and nuclear matrix transcription factor 4 (NMP-4) in the wild-type AGRE/H-OA chondrocyte complex.

CONCLUSION

These data suggest that the binding of p130(cas) and NMP-4 to the AGRE site regulates MMP-13 expression and may trigger the change in human chondrocytes from the L-OA state to the H-OA state.

Interaction partners for human ZNF384/CIZ/NMP4--zyxin as a mediator for p130CAS signaling?

Transcription factor ZNF384/CIZ/NMP4 was first cloned in rat as a p130Cas-binding protein and has a role in bone metabolism and spermatogenesis. It is recurrently involved in translocations in acute lymphoblastic leukemia. Translocations t(12;17) and t(12;22) fuse ZNF384 to RNA-binding proteins TAF15 and EWSR1, while a translocation t(12;19) generates an E2A/ZNF384 fusion. We screened for ZNF384 interacting proteins using yeast two-hybrid technology. In contrast to its rat homolog, human ZNF384 does not interact with p130CAS. Zyxin, PCBP1, and vimentin, however, were identified as ZNF384-binding partners. Given the interaction between human zyxin and p130CAS, these results suggest that zyxin indirectly enables the interaction of ZNF384 with p130CAS which is described in rat.

Cellular transformation of NIH3T3 fibroblasts by CIZ/NMP4 fusions

Molecular cloning of the translocations t(12;22)(p13;q12) and t(12;17)(p13;q11) in acute leukaemia showed that either EWSR1 or its homologue TAF15 are fused to the transcription factor CIZ. EWSR1 and TAF15 belong to the TET family (TLS/FUS, EWSR1 and TAF15) of proteins. TET fusions have been identified in both solid tumours and acute myeloid leukaemia. The novel 12p translocations directly implicated TET fusions in acute lymphoblastic leukaemia as well, and demonstrated the involvement of CIZ in haematopoietic malignancies. In addition, a new fusion E2A-CIZ was recently cloned as a result of a t(12;19)(p13;p13) in a patient with acute lymphoblastic leukaemia. NIH3T3 cells stably expressing TET-CIZ fusions display a transformed phenotype in a focus formation assay. We show here that E2A-CIZ also transforms 3T3 fibroblasts, suggesting that the addition of a transactivation domain to the CIZ protein is involved in this phenotype. An artificial VP16-CIZ construct reveals similar transforming properties, supporting this. We have then analysed the domains within TAF15-CIZ that are necessary for 3T3 fibroblast transformation. Deletion of the zinc fingers of CIZ resulted in loss of both DNA-binding and transforming properties of TAF15-CIZ, whereas deletion of the other functional domains of CIZ had no effect. Fusion of a transactivation domain to CIZ is suggestive for a transactivating function in transformation. Luciferase experiments indeed showed that E2A-CIZ as well as VP16-CIZ transactivates the MMP7 promoter. Taken together, our results reported here suggest that transformation of 3T3 fibroblasts by CIZ fusions is dependent on DNA-binding and might involve transactivation of CIZ target genes.

The nucleocytoplasmic shuttling protein CIZ reduces adult bone mass by inhibiting bone morphogenetic protein-induced bone formation

Osteoporosis is a major health problem; however, the mechanisms regulating adult bone mass are poorly understood. Cas-interacting zinc finger protein (CIZ) is a nucleocytoplasmic shuttling protein that localizes at cell adhesion plaques that form where osteoblasts attach to substrate. To investigate the potential role of CIZ in regulating adult bone mass, we examined the bones in CIZ-deficient mice. Bone volume was increased and the rates of bone formation were increased in CIZ-deficient mice, whereas bone resorption was not altered. CIZ deficiency enhanced the levels of mRNA expression of genes encoding proteins related to osteoblastic phenotypes, such as alkaline phosphatase (ALP) as well as osterix mRNA expression in whole long bones. Bone marrow cells obtained from the femora of CIZ-deficient mice revealed higher ALP activity in culture and formed more mineralized nodules than wild-type cells. CIZ deficiency enhanced bone morphogenetic protein (BMP)–induced osteoblastic differentiation in bone marrow cells in cultures, indicating that BMP is the target of CIZ action. CIZ deficiency increased newly formed bone mass after femoral bone marrow ablation in vivo. Finally, BMP-2–induced bone formation on adult mouse calvariae in vivo was enhanced by CIZ deficiency. These results establish that CIZ suppresses the levels of adult bone mass through inhibition of BMP-induced activation of osteoblasts.

Impaired spermatogenesis and male fertility defects in CIZ/Nmp4-disrupted mice

CIZ (Cas interacting zinc finger protein), also called Nmp4 (nuclear matrix protein 4), is a nucleo-cytoplasmic shuttling transcription factor that regulates the expression of collagen and matrix metalloproteinases. CIZ/Nmp4 was originally cloned by its binding to p130(Cas), a focal adhesion protein, and was recently shown to suppress BMP2 (bone mophogenetic protein 2) signalling. To explore the physiological role of CIZ/Nmp4, we disrupted CIZ/Nmp4-gene by inserting beta-galactosidase and neomycin resistance genes into the 2nd exon of CIZ/Nmp4-gene, which is utilized by all the sequenced alternative forms. CIZ-/- mice were born and grew to adulthood. Although they tend to be smaller than wild-type mice, no pathological abnormality was observed except in the testis. Histological analysis of the testes revealed variable degrees of spermatogenic cell degeneration within the seminiferous tubules of CIZ-/- mice, resembling the histology of the 'Germinal-cell aplasia with focal spermatogenesis'. Some of the CIZ-/- male mice developed infertility. TUNEL assay on testis sections revealed an increased occurrence of apoptosis of spermatogenic cells in the testes of CIZ-/- mice. CIZ/Nmp4 was co-localized with Smad1 in the testis, suggesting that a disregulation of BMP signalling could cause these phenotypes. These results suggest that CIZ/Nmp4 plays roles in the progress and the maintenance of spermatogenesis.

Two promoters control the mouse Nmp4/CIZ transcription factor gene

Nmp4/CIZ proteins (nuclear matrix protein 4/cas interacting zinc finger protein) contribute to gene regulation in bone, blood, and testis. In osteoblasts, they govern the magnitude of gene response to osteotropic factors like parathyroid hormone (PTH). Nmp4/CIZ is recurrently involved in acute leukemia and it has been implicated in spermatogenesis. However, these conserved proteins, derived from a single gene, are expressed in numerous tissues indicative of a more generalized housekeeping function in addition to their tissue-specific roles. To address how Nmp4/CIZ expression is governed, we characterized the 5' regulatory region of the mouse Nmp4 gene, located on chromosome 6. Two adjacent promoters P(1) [-2521 nucleotide (nt)/-597 nt] and P(2) (-2521 nt/+1 nt) initiate transcription of alternative first exons (U(1) and U(2)). Both promoters lack TATA and CCAAT boxes but contain initiator sites and CpG islands. Northern analysis revealed expression of both U(1) and U(2) in numerous adult tissues consistent with the constitutive and ubiquitous activity of a housekeeping gene. Sequence analysis identified numerous potential transcription factor-binding sites significant to osteogenesis, hematopoeisis, and gonadal development. The promoters are active in both osteoblast-like cells and in the M12 B-lymphocyte cell line. Low doses of PTH attenuated P(1)/P(2) activity in osteoblast-like cells. The Nmp4/CIZ promoters are autoregulated and deletion analysis identified regions that drive P(1) and P(2) basal activities as well as regions that contain positive and negative regulatory elements affecting transcription. The Nmp4/CIZ promoters comprise a genomic regulatory architecture that supports constitutive expression as well as cell- and tissue-specific regulation.

Induction of the MMP-14 gene in macrophages of the atherosclerotic plaque: role of SAF-1 in the induction process

Based on epidemiological and pathological studies, it is becoming increasingly clear that matrix metalloproteinases (MMPs) play an important role in the pathogenesis of atherosclerosis by participating in vascular remodeling, smooth muscle cell migration, and plaque disruption. MMP-14, because of its unique ability to cause pericellular degradation, its broad substrate specificity, its synthesis in an active form, and its ability to activate other matrix metalloproteinases, is recognized as a prominent member of this family. MMP-14 is detected at high levels in the atherosclerotic plaque. To understand the induction mechanism of MMP-14 under atherogenic conditions, we examined its expression pattern in response to oxidized low-density lipoproteins (ox-LDLs) that are believed to play an important role in atherogenesis. We report that in macrophages, ox-LDLs markedly elevate the levels of MMP-14 mRNA and protein. The cis-acting elements supporting this increase were identified to be present within -213 and -1 nucleotides of the MMP-14 promoter. DNase I protection assay revealed, within this region, two major elements, of which one serves as the DNA-binding site for SAF-1 transcription factor. Increased binding of SAF-1 to the MMP-14 promoter correlated with the transcriptional upregulation of MMP-14 gene. Furthermore, induction of endogenous MMP-14 gene, MMP-14 promoter driven reporter gene expression and MMP-2 processing activity during overexpression of SAF-1 and coexpression of SAF-1 and MMP-14 in the macrophages present in the atherosclerotic plaque implicate SAF-1 as a key regulator of MMP-14 gene induction in macrophage cells.

Regulation of the follicle-stimulating hormone beta gene by the LHX3 LIM-homeodomain transcription factor

FSH is a critical hormone regulator of gonadal function that is secreted from the pituitary gonadotrope cell. Human patients and animal models with mutations in the LHX3 LIM-homeodomain transcription factor gene exhibit complex endocrine diseases, including reproductive disorders with loss of FSH. We demonstrate that in both heterologous and pituitary gonadotrope cells, specific LHX3 isoforms activate the FSH beta-subunit promoter, but not the proximal LHbeta promoter. The related LHX4 mammalian transcription factor can also induce FSHbeta promoter transcription, but the homologous Drosophila protein LIM3 cannot. The actions of LHX3 are specifically blocked by a dominant negative LHX3 protein containing a Kruppel-associated box domain. Six LHX3-binding sites were characterized within the FSHbeta promoter, including three within a proximal region that also mediates gene regulation by other transcription factors and activin. Mutations of the proximal binding sites demonstrate their importance for LHX3 induction of the FSHbeta promoter and basal promoter activity in gonadotrope cells. Using quantitative methods, we show that the responses of the FSHbeta promoter to activin do not require induction of the LHX3 gene. By comparative genomics using the human FSHbeta promoter, we demonstrate structural and functional conservation of promoter induction by LHX3. We conclude that the LHX3 LIM homeodomain transcription factor is involved in activation of the FSH beta-subunit gene in the pituitary gonadotrope cell.

Zinc finger transcription factors in skeletal development

Cellular and molecular processes that regulate the development of skeletal tissues resemble those required for regeneration. Given the prevalence of degenerative skeletal disorders in an increasingly aging population, the molecular mechanisms of skeletal development must be understood in detail if novel strategies are to be developed in regenerative medicine. Research in this area over the past decade has revealed that cell differentiation is largely controlled at the level of gene transcription, which in turn is regulated by transcription factors. Transcription factors usually recognize and bind to specific DNA sequences in the promoter of target genes via characteristic DNA-binding domains. Although the gene family containing C2H2 zinc fingers as DNA-binding motifs is the largest family of transciptional regulators, with several hundred individual members in mammals, only a small but increasing number of zinc finger genes have been implicated in bone, cartilage, or tooth development. These zinc finger proteins (ZFPs) contain multiple structural motifs that require zinc to maintain their structural integrity and function. Interestingly, zinc deficiency is known to result in skeletal growth retardation and has been identified as a risk factor in the pathogenesis of osteoporosis. This review attempts to summarize our current state of knowledge regarding the role of ZFPs in the molecular regulation of skeletogenesis.

Nmp4/CIZ regulation of matrix metalloproteinase 13 (MMP-13) response to parathyroid hormone in osteoblasts

Parathyroid hormone (PTH) regulation of matrix metalloproteinase-13 (MMP-13) expression in osteoblasts contributes to normal bone turnover. The PTH response region of the rat MMP-13 gene spans nucleotides (nt) -148 to -38 and supports binding of numerous transcription factors, including Runx2, necessary for osteoblast differentiation, c-Fos/c-Jun, and Ets-1. These trans-acting proteins mediate hormone induction via incompletely defined combinatorial interactions. Within this region, adjacent to the distal Runx2 site, is a homopolymeric(dA:dT) element (-119/-110 nt) that conforms to the consensus site for the novel transcription factor nuclear matrix protein-4/cas interacting zinc finger protein (Nmp4/CIZ). This protein regulates bone cell expression of type I collagen and suppresses BMP2-enhanced osteoblast differentiation. The aim of this study was to determine whether Nmp4/CIZ contributes to MMP-13 basal transcription and PTH responsiveness in osteoblasts. Electrophoretic mobility shift analysis confirms Nmp4/CIZ binding within the MMP-13 PTH response region. Mutation of the Nmp4/CIZ element decreases basal activity of an MMP-13 promoter-reporter construct containing the first 1329 nt of the 5'-regulatory region, and overexpression of Nmp4/CIZ protein enhances the activity of the wild-type promoter. The same mutation of the homopolymeric(dA:dT) element enhances the MMP-13 response to PTH and PGE(2). Overexpression of Nmp4/CIZ diminishes hormone induction. Mutation of both the homopolymeric(dA:dT) element and the adjacent Runx2 site further augments the PTH response. On the basis of these data and previous studies, we propose that Nmp4/CIZ is a component of a multiprotein assemblage or enhanceosome within the MMP-13 PTH response region and that, within this context, Nmp4/CIZ promotes both basal expression and hormonal synergy.

Effects of clinorotation on COL1A1-EGFP gene expression

Bone-formation related gene plays a critical role in bone loss induced by space microgravity, however the exact mechanism is unclear. In this study, we aim to investigate the effect of microgravity on the activity of alpha 1(I) collagen (COL1A1) gene promoter and the expression of osteoblast-related genes. COL1A1 promoter was digested by restriction enzymes resulting in three DNA fragments. The fragments were ligated with the enhanced green fluorescent protein report gene, and subcloned into expression vectors. ROS17/2.8 cells transfected by these vectors were screened by G418, and enhanced green fluorescent protein (EGFP) positive colonies were isolated and cultured under clinostat condition. EGFP and Collagen type I expression level were detected by fluorescence intensity analysis and immunocytochemistry methods respectively. The results showed that the expression of EGFP and collagen type I was increased 24 h, 48 h after the cells were cultured under stimulated microgravity, illustrating that the activity of COL1A1 promoter might be increased. In conclusion, osteoblasts can compensatively increase the expression of type I collagen by enhancing the activity of COL1A1 promoter under short-term simulated microgravity conditions.

SPEER--a new family of testis-specific genes from the mouse

Differential cloning revealed a partial mRNA sequence expressed in the mouse testis, which on further molecular characterization proved to be a member of a new family of 14 transcribed genes. Six of the genes appear to be expressed pseudogenes. The remainder indicate an open reading frame of approximately 200-220 amino acids encoding proteins with a very high proportion of alpha helical secondary structure, comprising approximately 15% glutamate residues. Because of this property, the family has been named SPErm-associated glutamate (E)-Rich protein (SPEER). Three members were chosen for more detailed characterization: SPEER-1 (pseudogene), SPEER-2, and SPEER-4D. All three are expressed tissue specifically in the testis of mice, with only very weak expression evident in the rat testis but in no other species tested. Using reverse transcription-polymerase chain reaction (RT-PCR), all three transcripts can be detected also in the epididymis, presumably due to the presence of spermatozoa. All three transcripts are expressed to high levels in haploid germ cells at the spermatocyte-spermatid transition. SPEER-1 mRNA is present in the cytoplasm as a sense transcript, SPEER-2 appears to be made mostly as an antisense transcript, whereas SPEER-4D appears to be localized within a subcellular compartment as a conventional sense transcript. Codon usage analysis suggests that all but the pseudogenes can be expressed as protein, confirmed for SPEER-2 and SPEER-4D by in vitro transcription/translation. An antibody raised against a peptide region of SPEER-4D, which probably cross-reacts with other SPEER members, immunohistochemically stains the nuclei of early round spermatids. While there are no true homologies to other proteins in the genome databases, some motifs are present that suggest a relationship to nuclear matrix proteins, implying that the SPEER family is a new group of haploid sperm-specific nuclear factors.

The zinc finger transcription factor Zfp60 is a negative regulator of cartilage differentiation

The differentiation of many mesenchyme-derived cells, including cells that form bone and cartilage, is regulated at the level of gene transcription, but many of the factors involved in this regulation remain to be identified. In this study, a modified RNA fingerprinting technique was used to identify the KRAB domain zinc finger transcription factor Zfp60 as a candidate regulator of cell differentiation in mouse calvaria primary cultures. The highest expression of Zfp60 mRNA in vivo was found between embryonic day 11 (E11) and E15 during mouse embryonic development, coinciding with stages of active organ formation. The expression of Zfp60 mRNA and protein was analyzed further in mouse embryos during skeletal development. The most prominent expression was found in prehypertrophic chondrocytes, where it coincides with the expression of key regulators of chondrocyte maturation, Indian hedgehog (Ihh), and the parathyroid hormone-related peptide (PTHrP) receptor. Zfp60 mRNA was also found transiently expressed during chondrogenesis of C1 cells in vitro, preceding collagen type X expression and cellular hypertrophy. Overexpression of Zfp60 inhibited cartilage differentiation in the chondrogenic ATDC5 cell line. These results suggest a role for Zfp60 as a negative regulator of gene transcription, specifically during the development and/or differentiation of chondrocytes.

Analysis of gene expression profile in p130(Cas)-deficient fibroblasts

p130(Cas) (Cas) is a docking protein that becomes tyrosine phosphorylated in v-Src- or v-Crk-transformed cells and in integrin-stimulated cells. Cas -/- fibroblasts show defects in stress fiber formation, cell spreading, cell migration, and transformation by activated Src. To further characterize the role of Cas in signaling, we compared the expression profile in Cas -/- fibroblasts with that in Cas-re-expressing fibroblasts using the microarray methods. In Cas -/- fibroblasts, the expression of heme oxygenase 1 and caveolin-1 was reduced, but the expression of procollagen 1 alpha 1, procollagen 3 alpha 1, procollagen 11 alpha 1, elastin, periostin, TSC-36, and MARCKS was enhanced. The domains in Cas necessary for the change varied among these genes. Activated Src reduced the expression of most of these genes both in Cas -/- and in Cas +/+ fibroblasts. These results suggest the existence of signaling pathways that emanate from Cas to gene expression.

Osteoblast intracellular localization of Nmp4 proteins

Nmp4 proteins are transcription factors that contribute to the expression of type I collagen and many of the matrix metalloproteinase genes. Numerous Nmp4 isoforms have been identified. These proteins, all derived from a single gene, have from five to eight Cys(2)His(2) zinc fingers, the arrangement of which directs specific isoforms to nuclear matrix subdomains. Nmp4 isoforms also have an SH3 binding domain, typical of cytoplasmic docking proteins. Although recent evidence indicates that Nmp4 proteins also reside in the osteoblast cytoplasm, whether they localize to specific organelles or structures is not well defined. The intracellular localization of a protein is a determinant of its function and provides insights into its mechanism of action. As a first step toward determining the functional relationship between the cytoplasmic and nuclear Nmp4 compartments, we mapped their location in the osteoblast cytoplasm. Immunocytochemical analysis of osteoblasts demonstrated that Nmp4 antibodies labeled the mitochondria, colocalized with Golgi protein 58K, and lightly stained the cytoplasm. Western analysis using Nmp4 antibodies revealed a complex profile of protein bands in the nuclear, mitochondrial, and cytosolic fractions. Several of these proteins were specific to defined intracellular domains. Consistent with the western analyses, reverse transcription-polymerase chain reaction (RT-PCR) analysis detected previously uncharacterized Nmp4 isoforms. These data necessarily enlarge the known Nmp4 family from nuclear matrix transcription factors to a more widely extended class of intracellular proteins.