Preferential transformation of human neuronal cells by human adenoviruses and the origin of HEK 293 cells

Long CGG-repeat tracts are toxic to human cells: implications for carriers of Fragile X premutation alleles

People with 59-200 CGG.CCG-repeats in the 5' UTR of one of their FMR1 genes are at risk for Fragile X tremor and ataxia syndrome. Females are also at risk for premature ovarian failure. These symptoms are thought to be due to the presence of the repeats at the DNA and/or RNA level. We show here that long transcribed but untranslated CGG-repeat tracts are toxic to human cells and alter the expression of a wide variety of different genes including caspase-8, CYFIP, Neurotensin and UBE3A.

A splice variant of the Wilms' tumour suppressor Wt1 is required for normal development of the olfactory system

Neuronal lineage formation in the developing olfactory epithelium has been extensively studied at the cellular level, but little is known about the genes that control proliferation and differentiation of neuronal progenitor cells. Here, we report that the Wilms' tumour zinc-finger protein, Wt1, is required for normal formation of the olfactory epithelium. Wt1 was detected by immunohistochemistry in the developing olfactory epithelium of wild-type embryos between gestational days E9.5 and E18.5. Embryos with complete lack of Wt1 and embryos with selective ablation of the alternatively spliced Wt1(+KTS) isoform both had thinner olfactory epithelia and fewer neuronal progenitor cells than do normal animals. Mash1 and neurogenin 1, two basic helix-loop-helix transcription factors with critical functions during olfactory neuron development, were reduced in the Wt1(+KTS)-/- mutants compared with the wild-type mice. Stable expression of the Wt1(+KTS) isoform, but not of the Wt1(-KTS) variant, upregulated Mash1 mRNA and protein in vitro. The olfactory epithelia of mouse embryos, which lacked the Wt1(-KTS) protein, appeared normal. However, formation of the neural retina was severely impaired in the Wt1(-KTS)-/- mutants. These findings demonstrate that the Wt1(+KTS) protein, which has been proposed to play a role in mRNA processing, acts upstream of Mash1 to promote the development of the olfactory epithelium. Furthermore, neuron formation depends on distinct functions of alternatively spliced Wt1 products in the embryonic retina and the olfactory epithelium.

Transcriptomic and proteomic responses of human renal HEK293 cells to uranium toxicity

The industrial use of uranium, in particular depleted uranium, has pin-pointed the need to review its chemical impact on human health. Global methodologies, applied to the field of toxicology, have demonstrated their applicability to investigation of fine molecular mechanisms. This report illustrate the power of toxicogenomics to evaluate the involvement of certain genes or proteins in response to uranium. We particularly show that 25% of modulated genes concern signal transduction and trafficking, that the calcium pathway is heavily disturbed and that nephroblastomas-related genes are involved (WIT-1, STMN1, and STMN2). A set of 18 genes was deregulated whatever the concentration of toxicant, which could constitute a signature of uranium exposure. Moreover, a group of downregulated genes, with corresponding disappearing proteins (HSP90, 14-3-3 protein, HMGB1) in two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), are good candidates for use as biomarkers of uranium effects. These results reveal a cross-checking between transcriptomic and proteomic technologies. Moreover, our temporal gene expression profiles suggest the existence of a concentration threshold between adaptive response and severe cell deregulation. Our results confirm the involvement of genes already described and also provide new highlights on cellular response to uranium.

Enhancement of benzodiazepine binding sites following chronic treatment with flumazenil

The aim of this study was to improve our knowledge of the mechanisms leading to adaptive changes in gamma-aminobutyric acid(A) (GABA(A)) receptors following chronic drug treatment. Exposure (48 h) of human embryonic kidney (HEK 293) cells stably expressing recombinant alpha1beta2gamma2S GABA(A) receptors to the antagonist of benzodiazepine binding sites, flumazenil (5 microM), enhanced the maximum number (B(max)) and the equilibrium dissociation constant (K(d)) of [3H]flunitrazepam binding sites. The flumazenil-induced enhancement in B(max) was potentiated by GABA (50 microM) and reduced by the GABA(A) receptor antagonist, bicuculline (100 microM). Flumazenil-induced enhancement in K(d) was affected by neither of these treatments. GABA (50 microM) enhanced the density of [3H]flunitrazepam binding sites, and this enhancement was greater in the presence of diazepam (1 microM). The results suggest that chronic flumazenil treatment up-regulates in a bicuculline-sensitive manner benzodiazepine binding sites at stably expressed GABA(A) receptors.

Chronic exposure of cells expressing recombinant GABAA receptors to benzodiazepine antagonist flumazenil enhances the maximum number of benzodiazepine binding sites

The aim of this study was to better understand the mechanisms that underlie adaptive changes in GABAA receptors following their prolonged exposure to drugs. Exposure (48 h) of human embryonic kidney (HEK) 293 cells stably expressing recombinant alpha1beta2gamma2S GABAA receptors to flumazenil (1 or 5 microM) in the presence of GABA (1 microM) enhanced the maximum number (Bmax) of [3H]flunitrazepam binding sites without affecting their affinity (Kd). The flumazenil-induced enhancement in Bmax was not counteracted by diazepam (1 microM). GABA (1 nM-1 mM) enhanced [3H]flunitrazepam binding to membranes obtained from control and flumazenil-pretreated cells in a concentration-dependent manner. No significant differences were observed in either the potency (EC50) or efficacy (Emax) of GABA to potentiate [3H]flunitrazepam binding. However, in flumazenil pretreated cells the basal [3H]flunitrazepam and [3H]TBOB binding were markedly enhanced. GABA produced almost complete inhibition of [3H]TBOB binding to membranes obtained from control and flumazenil treated cells. The potencies of GABA to inhibit this binding, as shown by a lack of significant changes in the IC50 values, were not different between vehicle and drug treated cells. The results suggest that chronic exposure of HEK 293 cells stably expressing recombinant alpha1beta2gamma2S GABAA receptors to flumazenil (in the presence of GABA) up-regulates benzodiazepine and convulsant binding sites, but it does not affect the allosteric interactions between these sites and the GABA binding site. Further studies are needed to elucidate these phenomena.

Overexpression of Enzymatically Active Human Cytosolic and Mitochondrial Thioredoxin Reductase in HEK-293 Cells

The mammalian thioredoxin reductases (TrxR) are selenoproteins containing a catalytically active selenocysteine residue (Sec) and are important enzymes in cellular redox control. The cotranslational incorporation of Sec, necessary for activity, is governed by a stem-loop structure in the 3'-untranslated region of the mRNA and demands adequate selenium availability. The complicated translation machinery required for Sec incorporation is a major obstacle in isolating mammalian cell lines stably overexpressing selenoproteins. In this work we report on the development and characterization of stably transfected human embryonic kidney 293 cells that overexpress enzymatically active selenocysteine-containing cytosolic TrxR1 or mitochondrial TrxR2. We demonstrate that the overexpression of selenium-containing TrxR1 results in lower expression and activity of the endogenous selenoprotein glutathione peroxidase and that the activity of overexpressed TrxRs, rather than the protein amount, can be increased by selenium supplementation in the cell growth media. We also found that the TrxR-overexpressing cells grew slower over a wide range of selenium concentrations, which was an effect apparently not related to increased apoptosis nor to fatally altered intracellular levels of reactive oxygen species. Most surprisingly, the TrxR1- or TrxR2-overexpressing cells also induced novel expression of the epithelial markers CK18, CK-Cam5.2, and BerEP4, suggestive of a stimulation of cellular differentiation.

Molecular basis of the extreme dilution mottled mouse mutation: a combination of coding and noncoding genomic alterations

Tyrosinase is the rate-limiting enzyme in melanin biosynthesis. It is an N-glycosylated, copper-containing transmembrane protein, whose post-translational processing involves intracytoplasmic movement from the endoplasmic reticulum to the Golgi and, eventually, to the melanosome. The expression of the tyrosinase (Tyr) gene is controlled by several regulatory regions including a locus control region (LCR) located 15 kb upstream from the promoter region. The extreme dilution mottled mutant mice (Tyrc-em) arose spontaneously at the MRC Institute in Harwell (United Kingdom) from a chinchilla-mottled mutant (Tyrc-m) stock, whose molecular basis corresponds to a rearrangement of 5'-upstream regulatory sequences including the LCR of the Tyr gene. Tyrc-em mice display a variegated pigmentation pattern in coat and eyes, in agreement with the LCR translocation, but also show a generalized hypopigmented phenotype, not seen in Tyrc-m mice. Genomic analyses of Tyrc-em mice showed a C1220T nucleotide substitution within the Tyr encoding region, resulting in a T373I amino acid change, which abolishes an N-glycosylation sequon located in the second metal ion binding site of the enzyme. Tyrosinase from Tyrc-em displayed a reduced enzymatic activity in vivo and in vitro, compared with wild-type enzyme. Deglycosylation studies showed that the mutant protein has an abnormal glycosylation pattern and is partially retained in the endoplasmic reticulum. We conclude that the phenotype of the extreme dilution mottled mouse mutant is caused by a combination of coding and noncoding genomic alterations resulting in several abnormalities that include suboptimal gene expression, abnormal protein processing, and reduced enzymatic activity.

Contactin associates with sodium channel Nav1.3 in native tissues and increases channel density at the cell surface

The upregulation of voltage-gated sodium channel Na(v)1.3 has been linked to hyperexcitability of axotomized dorsal root ganglion (DRG) neurons, which underlies neuropathic pain. However, factors that regulate delivery of Na(v)1.3 to the cell surface are not known. Contactin/F3, a cell adhesion molecule, has been shown to interact with and enhance surface expression of sodium channels Na(v)1.2 and Na(v)1.9. In this study we show that contactin coimmunoprecipitates with Na(v)1.3 from postnatal day 0 rat brain where this channel is abundant, and from human embryonic kidney (HEK) 293 cells stably transfected with Na(v)1.3 (HEK-Na(v)1.3). Purified GST fusion proteins of the N and C termini of Na(v)1.3 pull down contactin from lysates of transfected HEK 293 cells. Transfection of HEK-Na(v)1.3 cells with contactin increases the amplitude of the current threefold without changing the biophysical properties of the channel. Enzymatic removal of contactin from the cell surface of cotransfected cells does not reduce the elevated levels of the Na(v)1.3 current. Finally, we show that, similar to Na(v)1.3, contactin is upregulated in axotomized DRG neurons and accumulates within the neuroma of transected sciatic nerve. We propose that the upregulation of contactin and its colocalization with Na(v)1.3 in axotomized DRG neurons may contribute to the hyper-excitablity of the injured neurons.

Tyrosinase-related proteins suppress tyrosinase-mediated cell death of melanocytes and melanoma cells

The synthesis of melanin intermediates through tyrosinase (TYR) involves the production of cytotoxic free radicals. By using recombinant adenoviruses that express TYR, tyrosinase-related protein 1 (TYRP1) or DOPAchrome tautomerase (DCT), we analyzed the biological function of these proteins with regard to melanin production and the growth of melanocytes, fibroblasts, melanoma cells and nonmelanoma cancer cells. High-level expression of TYR produced newly synthesized melanin and induced cell death in all of these cells. However, when TYRP1 or DCT was coexpressed with TYR in melanocytes and melanoma cells, TYR-mediated cell death was clearly decreased. This decrease was not observed in nonmelanocytic cells. Western blot analysis and measurement of enzyme activity revealed that the expression of TYRP1 or DCT had little effect on the amount or activity of cointroduced TYR in either the melanocytic or nonmelanocytic cells. In cells expressing both TYR and TYRP1 or TYR and DCT, the total amount of melanin and/or eumelanin increased substantially more than that in cells expressing TYR alone. On the other hand, the level of pheomelanin was similar in these three cell types. These findings suggest that TYRP1 and DCT play an important role in suppressing TYR-mediated cytotoxicity in melanocytic cells without decreasing TYR expression and/or activity. These biological activities of TYRP1 and DCT may work through the interaction with TYR in melanosomal compartment.

Poliovirus receptor CD155-targeted oncolysis of glioma

Cell adhesion molecules of the immunoglobulin superfamily are aberrantly expressed in malignant glioma. Amongst these, the human poliovirus receptor CD155 provides a molecular target for therapeutic intervention with oncolytic poliovirus recombinants. Poliovirus has been genetically modified through insertion of regulatory sequences derived from human rhinovirus type 2 to selectively replicate within and destroy cancerous cells. Efficacious oncolysis mediated by poliovirus derivatives depends on the presence of CD155 in targeted tumors. To prepare oncolytic polioviruses for clinical application, we have developed a series of assays in high-grade malignant glioma (HGL) to characterize CD155 expression levels and susceptibility to oncolytic poliovirus recombinants. Analysis of 6 HGL cases indicates that CD155 is expressed in these tumors and in primary cell lines derived from these tumors. Upregulation of the molecular target CD155 rendered explant cultures of all studied tumors highly susceptible to a prototype oncolytic poliovirus recombinant. Our observations support the clinical application of such agents against HGL.

Activation of Adenovirus Type 2 Early Region 4 ORF4 Cytoplasmic Death Function by Direct Binding to Src Kinase Domain

Adenovirus type 2 (Ad2) early region 4 ORF4 (E4orf4) triggers a major death pathway that requires its accumulation in cellular membranes and its tyrosine phosphorylation. This program is regulated by Src family kinases and triggers a potent ZVAD (benzyloxycarbonyl-VAD)- and Bcl2-resistant cell death response in human-transformed cells. How E4orf4 deregulates Src-dependent signaling is unknown. Here we provide strong evidence that a physical interaction requiring the kinase domain of Src and the arginine-rich motif of E4orf4 is involved. The Src binding domain of E4orf4 overlaps with, but is distinct from that of the Balpha subunit of protein phosphatase 2A (PP2A-Balpha) and some E4orf4 complexes contain both PP2A and Src. Functional assays using mutant E4orf4 revealed that deregulation of Src signaling, activation of the Jun kinase pathway, and cell blebbing were all critically dependent on Src binding. In contrast, PP2A-Balpha binding per se was not required to engage the Src-dependent death pathway but was more critical for triggering a distinct death activity. Both E4orf4 death activities were manifested within a given cell population, were typified by distinct morphological features, and contributed to overall cell killing, although to different extents in various cell types. We conclude that E4orf4 binding to the Src kinase domain leads to deregulation of Src signaling and plays a crucial role in induction of the cytoplasmic death pathway. Nonetheless, both Src and PP2A enzymes are critical targets of E4orf4 that likely cooperate to trigger E4orf4-induced tumor cell killing and whose relative contributions may vary in function of the cellular background.

Kidney, blood, and endothelium: Developmental expression of stem cell leukemia during nephrogenesis

BACKGROUND

In vertebrates the hematopoietic and renal tissues share a common mesodermal origin. Recently, we have analyzed global gene expression during human nephrogenesis and observed up-regulation of stem cell leukemia (SCL), a transcription factor critical for hematopoietic and endothelial lineage specification. Here we characterize the expression of SCL along with its distinct 3' hematopoietic and endothelial enhancer (SCL 3'En) during kidney development.

METHODS

mRNA and protein expression of SCL were examined in developing murine and human kidneys by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. The activity of SCL 3'En was examined by X-galactosidase (X-gal) staining of embryonic kidneys obtained from SCL +6E5/lacZ/3'En transgenic mice and by reporter lacZ assay in various renal cell lines.

RESULTS

We found developmental regulation of SCL mRNA with highest levels of expression in embryonic day 17 (E17) mouse kidneys and lowest in postnatal and adult kidneys. Immunostaining of human fetal kidneys demonstrated the protein predominantly in the nephrogenic cortex and particularly in mesenchymal cells and developing glomeruli. Similarly, SCL +6E5/lacZ/3'En transgenic kidneys showed prominent lacZ staining in cells resembling undifferentiated mesoderm cells in close proximity to S and comma-shaped primitive nephrons and in peritubular and glomerular vessel endothelium. The SCL 3'En was activated in the human embryonic kidney cell line (HEK 293), but not in cell lines derived from adult kidney.

CONCLUSION

These observations suggest a possible role for SCL in renal vasculogenesis. Undifferentiated mesenchymal cells expressing SCL during early nephrogenesis might represent putative progenitors that can simultaneously give rise to kidney, blood, and endothelium.

Iterative Group Analysis (iGA): a simple tool to enhance sensitivity and facilitate interpretation of microarray experiments

Background

The biological interpretation of even a simple microarray experiment can be a challenging and highly complex task. Here we present a new method (Iterative Group Analysis) to facilitate, improve, and accelerate this process.

Results

Our Iterative Group Analysis approach (iGA) uses elementary statistics to identify those functional classes of genes that are significantly changed in an experiment and at the same time determines which of the class members are most likely to be differentially expressed. iGA does not require that all members of a class change and is therefore robust against imperfect class assignments, which can be derived from public sources (e.g. GeneOntologies) or automated processes (e.g. key word extraction from gene names).

In contrast to previous non-iterative approaches, iGA does not depend on the availability of fixed lists of differentially expressed genes, and thus can be used to increase the sensitivity of gene detection especially in very noisy or small data sets. In the extreme, iGA can even produce statistically meaningful results without any experimental replication.

The automated functional annotation provided by iGA greatly reduces the complexity of microarray results and facilitates the interpretation process. In addition, iGA can be used as a fast and efficient tool for the platform-independent comparison of a microarray experiment to the vast number of published results, automatically highlighting shared genes of potential interest.

Conclusions

By applying iGA to a wide variety of data from diverse organisms and platforms we show that this approach enhances and accelerates the interpretation of microarray experiments.

LRRN6A/LERN1 (leucine-rich repeat neuronal protein 1), a novel gene with enriched expression in limbic system and neocortex

Human chromosome 15q24-q26 is a very complex genomic region containing several blocks of segmental duplications to which susceptibility to anxiety disorders has been mapped (Gratacos et al., 2001, Cell, 106, 367-379; Pujana et al., 2001, Genome Res., 11, 98-111). Through an in silico gene content analysis of the 15q24-q26 region we have identifie1d a novel gene, LRRN6A (leucine-rich repeat neuronal 6A), and confirmed its location to the centromeric end of this complex region. LRRN6A encodes a transmembrane leucine-rich repeat protein, LERN1 (leucine-rich repeat neuronal protein 1), with similarity to proteins involved in axonal guidance and migration, nervous system development and regeneration processes. The identification of homologous genes to LRRN6A on chromosomes 9 and 19 and the orthologous genes in the mouse genome and other organisms suggests that LERN proteins constitute a novel subfamily of LRR (leucine-rich repeat)-containing proteins. The LRRN6A expression pattern is specific to the central nervous system, highly and broadly expressed during early stages of development and gradually restricted to forebrain structures as development proceeds. Expression level in adulthood is lower in general but remains stable and significantly enriched in the limbic system and cerebral cortex. Taken together, the confirmation of LRRN6A's expression profile, its predicted protein structure and its similarity to nervous system-expressed LRR proteins with essential roles in nervous system development and maintenance suggest that LRRN6A is a novel gene of relevance in the molecular and cellular neurobiology of vertebrates.

Visual cycle retinoid processing proteins are present in HEK293S cells

In HEK293S cells expressing opsin, rhodopsin regenerates on addition of all-trans retinol. This study was to determine if key proteins in the retinal pigment epithelium (RPE) are present in these cells. Cellular retinoid binding protein, cellular retinoic-acid binding protein, RPE65, caveolin-1-alpha- and -beta-isoforms, interphotoreceptor retinoid binding protein, and 11-cis retinol dehydrogenase, but not lecithin:retinol acyltransferase (LRAT), were identified by Western blot analysis. LRAT transcripts were found by RT-PCR and Southern blot analysis. Small interference RNA specific to LRAT reduced ester formation, confirming that the enzyme is present. Therefore, HEK293S cells contain the functional components of the retinoid cycle found in the RPE.

Isolation of human NURF: a regulator of Engrailed gene expression

The modification of chromatin structure is an important regulatory mechanism for developmental gene expression. Differential expression of the mammalian ISWI genes, SNF2H and SNF2L, has suggested that they possess distinct developmental roles. Here we describe the purification and characterization of the first human SNF2L-containing complex. The subunit composition suggests that it represents the human ortholog of the Drosophila nucleosome-remodeling factor (NURF) complex. Human NURF (hNURF) is enriched in brain, and we demonstrate that it regulates human Engrailed, a homeodomain protein that regulates neuronal development in the mid-hindbrain. Furthermore, we show that hNURF potentiates neurite outgrowth in cell culture. Taken together, our data suggess a role for an ISWI complex in neuronal growth.

Cell transformation by human adenoviruses

The last 40 years of molecular biological investigations into human adenoviruses have contributed enormously to our understanding of the basic principles of normal and malignant cell growth. Much of this knowledge stems from analyses of their productive infection cycle in permissive host cells. Also, initial observations concerning the carcinogenic potential of human adenoviruses subsequently revealed decisive insights into the molecular mechanisms of the origins of cancer, and established adenoviruses as a model system for explaining virus-mediated transformation processes. Today it is well established that cell transformation by human adenoviruses is a multistep process involving several gene products encoded in early transcription units 1A (E1A) and 1B (E1B). Moreover, a large body of evidence now indicates that alternative or additional mechanisms are engaged in adenovirus-mediated oncogenic transformation involving gene products encoded in early region 4 (E4) as well as epigenetic changes resulting from viral DNA integration. In particular, detailed studies on the tumorigenic potential of subgroup D adenovirus type 9 (Ad9) E4 have now revealed a new pathway that points to a novel, general mechanism of virus-mediated oncogenesis. In this chapter, we summarize the current state of knowledge about the oncogenes and oncogene products of human adenoviruses, focusing particularly on recent findings concerning the transforming and oncogenic properties of viral proteins encoded in the E1B and E4 transcription units.

Prolonged exposure to γ-aminobutyric acid up-regulates stably expressed recombinant α1β2γ2s GABAA receptors

The aim of this study was to better understand the mechanisms that underlie adaptive changes in GABA(A) receptors following their prolonged exposure to drugs. Exposure (48 and/or 96 h) of human embryonic kidney (HEK 293) cells stably expressing recombinant alpha1beta2gamma2s GABA(A) receptors for gamma-aminobutyric (GABA, 1 mM) and muscimol (100 microM), but not for diazepam (1 microM), enhanced the maximum number (B(max)) of [3H]flunitrazepam binding sites without affecting their affinity (K(d)). The GABA-induced enhancement in B(max) was reduced by the GABA receptor antagonist, bicuculline (100 microM), and by cycloheximide (10 microl/ml), a protein synthesis inhibitor. GABA (100 microM) enhanced the affinity of [3H]flunitrazepam binding to vehicle- and GABA-pretreated, but not to diazepam-pretreated, HEK 293 cells. The results suggest that chronic GABA treatment up-regulates stably expressed GABA(A) receptors, presumably by stimulating their synthesis. Unlike chronic diazepam, which produced functional uncoupling of GABA and benzodiazepine binding sites, chronic GABA failed to produce this effect.

Some morphological, growth, and genomic properties of human cells chronically infected with porcine endogenous retrovirus (PERV)

A major concern in using porcine organs for transplantation is the potential of transmission of porcine endogenous retrovirus (PERV). To investigate the long-term effects of PERV infection on human cells, human embryonic kidney cell line HEK-293 infected with PERV PK-15 was maintained for up to 72 passages and samples were harvested at intervals for use in morphological, growth, and genomic analyses. Morphology, DNA content/cell, and doubling time of uninfected and infected cells were similar. Restriction fragment length polymorphism (RFLP) analysis of PCR-amplified nearly full-length PERV genome showed no alterations in band pattern. RFLP analysis of the long terminal repeats (LTR) showed some changes in band pattern, but not in length. Southern blot analysis of genomic DNA of infected cells indicated random integration of PERV without structural alterations in proviral genome. Semi-quantitative PCR demonstrated a gradual increase of proviral load in the infected cells. Sequence analysis of the LTR region of PERV from infected cells indicated a relatively low rate (6.0 × 10–4/bp or about 2 × 10–6/bp/generation) of mutation. There were also indications of recombination of PERV strains A and B. Finally, PERV infection had no effect on transcription of human endogenous retrovirus-K (HERV-K) genes. Together, no significant effect attributable to PERV infection was evident on chronically PERV-infected HEK-293 cells.Key words: porcine endogenous retrovirus (PERV), human endogenous retrovirus-K (HERV-K), xenotransplantation, zoonosis.

OFD1, the gene mutated in oral-facial-digital syndrome type 1, is expressed in the metanephros and in human embryonic renal mesenchymal cells

Oral-facial-digital syndrome type 1 (OFD1) causes polycystic kidney disease (PKD) and malformations of the mouth, face and digits. Recently, a gene on Xp22, OFD1, was reported to be mutated in a limited set of OFD1 patients. This study describes mutation analysis in six further OFD1 families. Additionally, gene expression was sought in human development. In two OFD1 kindreds affected by PKD, a frameshift mutation and a splice-site mutation were detected. In four apparently sporadic cases, three frameshift and a missense mutation were found. Using RT-PCR of RNA from first-trimester normal human embryos, both alternative splice forms of mRNA (OFD1a and OFD1b) were found to be widely expressed in organogenesis. Northern blot detected OFD1 mRNA in metanephros, brain, tongue, and limb, all organs affected in the syndrome. A polyclonal antibody directed to a C-terminal OFD1a epitope detected a 120-kD protein in the metanephros and in human renal mesenchymal cell lines. In normal human embryos, OFD1a immunolocalized to the metanephric mesenchyme, oral mucosa, nasal and cranial cartilage, and brain. Moreover, using normal human renal mesenchymal cell lines, the immunoreactive protein colocalized with gamma-tubulin, suggesting that OFD1 is associated with the centrosome. First, it is concluded that OFD1 mutations would generally be predicted to result in unstable transcripts or nonfunctional proteins. Second, OFD1 is expressed in human organogenesis; on the basis of the metanephric expression pattern, the results suggest that OFD1 plays a role in differentiation of metanephric precursor cells.

The ERK/MAPK pathway regulates the activity of the human tissue factor pathway inhibitor-2 promoter

Human tissue factor pathway inhibitor-2 (hTFPI-2) is a 32-kDa serine protease inhibitor that is associated with the extracellular matrix. hTFPI-2 inhibits several extracellular matrix-degrading serine proteases and may play a role in tumor invasion and metastasis. To study the signal transduction pathway that leads to the activation of the hTFPI-2, we cloned the potential promoter region of this gene adjacent to a heterologous luciferase reporter gene. Phorbol 12-myristate 13-acetate (PMA) induced the luciferase reporter gene in HEK293 cells and other epithelial cell lines, such as the human lung carcinoma A549 cells, the breast carcinoma MCF7 cells, and the cervical HeLa cells. This PMA induction was blocked with the MEK inhibitor UO126, suggesting that the PMA-induced activation of the hTFPI-2 promoter is mediated through MEK. Furthermore, epidermal growth factor induced the luciferase reporter gene in HeLa cells. Cotransfection of the luciferase construct with constitutively active components of the Ras/Raf/MEK/ERK pathway in EcR-293 cells lead to a 7- to 92-fold induction of the luciferase reporter gene, indicating that regulation of hTFPI-2 is mediated through this pathway. A series of luciferase reporter gene constructs with progressive deletions of the 5'-flanking region suggested that the minimal basal promoter activity is located between nucleotide positions -89 and -384, whereas the minimal inducible promoter activity is between -89 and -222. We have used the computer program TFSEARCH and mutagenesis to analyze potential transcription factor binding sites. We identified an AP-1 binding site at nucleotide position -156 (inducible activity) and a Sp1 site at position -134 (basal activity) as potential cis-acting elements in the promoter region of the hTFPI-2.