Olink proteomics analysis uncovers inflammatory proteins in patients with different states of bipolar disorder

STUDY DESIGN

A prospective study.

BACKGROUND

This study aims to investigate the relationship between different states of bipolar disorder (BD) and plasma inflammatory proteins, which may be used as their biomarkers.

MATERIALS AND METHODS

We totally collected admission plasma from 16 healthy subjects and 32 BD patients, including 16 patients with BD manic episodes (BD-M) and 16 patients with BD depressive episodes (BD-D). Ten samples in each group were analyzed by proximity extension assays of 92 inflammation-related proteins, and all samples were verified by ELISA. Receiver-operating characteristic (ROC) curve analysis was performed to identify the diagnostic ability and cut-off values of potential biomarkers.

RESULTS

Our findings showed that BD patients had significantly higher levels of IL6, MCP-1, TGF-α, IL8, and IL10-RB in comparison with healthy subjects, and their cut-off values were 0.531 pg/ml, 0.531 pg/ml, 0.469 pg/ml, 0.406 pg/ml, and 0.406 pg/ml, respectively. The levels of IL6, MCP-1, TGF-α, and IL8 in BD-M patients were significantly greater than in healthy individuals, and their cut-off values were 0.813 pg/ml, 0.688 pg/ml, 0.438 pg/ml, and 0.625 pg/ml, respectively. Moreover, we found cut-off values of 0.500 pg/mL and 0.688 ng/mL for TGF-α and β-NGF, respectively, even though the levels in the BD-D group were much higher than in the control group. Furthermore, BD-M patients had significantly higher levels of IL6, FGF-19, IFN-γ, and IL-17C in comparison with BD-D patients. Likewise, 0.687 pg/ml, 0.500 pg/ml, 0.438 pg/ml, and 0.375 pg/ml were their cut-off values, respectively. Our findings also showed that the combination of these proteins had the highest diagnostic accuracy.

CONCLUSIONS

Our findings showed that plasma inflammatory proteins were related to BD and its subtypes, which may be utilized as potential biomarkers of different stages of BD. Furthermore, we also found their cut-off values and their combinations to have the highest diagnostic accuracy, providing clinicians with a new method to rapidly differentiate BD and its subtypes and manage early targeted interventions.

TGF-α/EGFR signaling promotes lipopolysaccharide-induced abnormal elastin deposition and alveolar simplification

Bronchopulmonary dysplasia (BPD) is characterized by shortened secondary septa and fewer, larger alveoli. Elastin deposition to the distal tips of the secondary septa is critical for elongation of the secondary septa. Alveolar myofibroblasts, which are thought to migrate to the septal tips during alveolarization, are mainly responsible for elastin production and deposition. Antenatal exposure to inflammation induces abnormal elastin deposition, thereby increasing the risk of developing BPD. Here, we found that lipopolysaccharide (LPS) significantly increased the expression of transforming growth factor-α (TGF-α) in an LPS-induced rat model of BPD and in LPS-treated human pulmonary epithelial cells (BEAS-2B). In addition, in vitro experiments suggested that LPS upregulated TGF-α expression via toll-like receptor 4 (TLR4)/tumor necrosis factor α-converting enzyme (TACE) signaling. Increased TGF-α levels via its receptor epidermal growth factor receptor (EGFR)-induced lysyl oxidase (LOX) overactivation and cell division cycle 42 (Cdc42) activity inhibition of myofibroblasts. Similarly, in vivo LOX overactivation and inhibition of Cdc42 activity were observed in the lungs of LPS-exposed pups. LOX overactivation led to abnormal elastin deposition, and inhibition of Cdc42 activity disturbed the directional migration of myofibroblasts and disrupted elastin localization. Most importantly, the EGFR inhibitor erlotinib partially rescued LOX overactivation and Cdc42 activity inhibition, and improved elastin deposition and alveolar development in antenatal LPS-treated rats. Taken together, our data suggest that TGF-α/EGFR signaling is critically involved in the regulation of elastin deposition and represents a novel therapeutic target.

Association of circulating inflammatory proteins with type 2 diabetes mellitus and its complications: a bidirectional Mendelian randomization study

Background

Increasing evidence indicates that immune response underlies the pathology of type 2 diabetes (T2D). Nevertheless, the specific inflammatory regulators involved in this pathogenesis remain unclear.

Methods

We systematically explored circulating inflammatory proteins that are causally associated with T2D via a bidirectional Mendelian randomization (MR) study and further investigated them in prevalent complications of T2D. Genetic instruments for 91 circulating inflammatory proteins were derived from a genome-wide association study (GWAS) that enrolled 14,824 predominantly European participants. Regarding the summary-level GWASs of type 2 diabetes, we adopted the largest meta-analysis of European population (74,124 cases vs. 824,006 controls) and a prospective nested case-cohort study in Europe (9,978 cases vs. 12,348 controls). Summary statistics for five complications of T2D were acquired from the FinnGen R9 repository. The inverse variance-weighted method was applied as the primary method for causal inference. MR-Egger, weighted median and maximum likelihood methods were employed as supplementary analyses. Results from the two T2D studies were combined in a meta-analysis. Sensitivity analyses and phenotype-wide association studies (PheWAS) were performed to detect heterogeneity and potential horizontal pleiotropy in the study.

Results

Genetic evidence indicated that elevated levels of TGF-α (OR = 1.16, 95% CI = 1.15-1.17) and CX3CL1 (OR = 1.30, 95% CI = 1.04-1.63) promoted the occurrence of T2D, and increased concentrations of FGF-21 (OR = 0.87, 95% CI = 0.81-0.93) and hGDNF (OR = 0.96, 95% CI = 0.95-0.98) mitigated the risk of developing T2D, while type 2 diabetes did not exert a significant influence on said proteins. Elevated levels of TGF-α were associated with an increased risk of ketoacidosis, neurological complications, and ocular complications in patients with T2D, and increased concentrations of FGF-21 were potentially correlated with a diminished risk of T2D with neurological complications. Higher levels of hGDNF were associated with an increased risk of T2D with peripheral vascular complications, while CX3CL1 did not demonstrate a significant association with T2D complications. Sensitivity analyses and PheWAS further ensure the robustness of our findings.

Conclusion

This study determined four circulating inflammatory proteins that affected the occurrence of T2D, providing opportunities for the early prevention and innovative therapy of type 2 diabetes and its complications.

TGFA expression is associated with poor prognosis and promotes the development of cervical cancer

Cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) are the second most common cancers in women aged 20-39. While HPV screening can help with early detection of cervical cancer, many patients are already in the medium to late stages when they are identified. As a result, searching for novel biomarkers to predict CESC prognosis and propose molecular treatment targets is critical. TGFA is a polypeptide growth factor with a high affinity for the epidermal growth factor receptor. Several studies have shown that TGFA can improve cancer growth and progression, but data on its impact on the occurrence and advancement of CESC is limited. In this study, we used clinical data analysis and bioinformatics techniques to explore the relationship between TGFA and CESC. The results showed that TGFA was highly expressed in cervical cancer tissues and cells. TGFA knockdown can inhibit the proliferation, migration and invasion of cervical cancer cells. In addition, after TGFA knockout, the expression of IL family and MMP family proteins in CESC cell lines was significantly reduced. In conclusion, TGFA plays an important role in the occurrence and development of cervical cancer. Therefore, TGFA may become a new target for cervical cancer treatment.

Dynamic tuft cell expansion during gastric metaplasia and dysplasia

Tuft cells are chemosensory cells associated with luminal homeostasis, immune response, and tumorigenesis in the gastrointestinal tract. We aimed to elucidate alterations in tuft cell populations during gastric atrophy and tumorigenesis in humans with correlative comparison to relevant mouse models. Tuft cell distribution was determined in human stomachs from organ donors and in gastric pathologies including Ménétrier's disease, Helicobacter pylori gastritis, intestinal metaplasia (IM), and gastric tumors. Tuft cell populations were examined in Lrig1-KrasG12D , Mist1-KrasG12D , and MT-TGFα mice. Tuft cells were evenly distributed throughout the entire normal human stomach, primarily concentrated in the isthmal region in the fundus. Ménétrier's disease stomach showed increased tuft cells. Similarly, Lrig1-Kras mice and mice overexpressing TGFα showed marked foveolar hyperplasia and expanded tuft cell populations. Human stomach with IM or dysplasia also showed increased tuft cell numbers. Similarly, Mist1-Kras mice had increased numbers of tuft cells during metaplasia and dysplasia development. In human gastric cancers, tuft cells were rarely observed, but showed positive associations with well-differentiated lesions. In mouse gastric cancer xenografts, tuft cells were restricted to dysplastic well-differentiated mucinous cysts and were lost in less differentiated cancers. Taken together, tuft cell populations increased in atrophic human gastric pathologies, metaplasia, and dysplasia, but were decreased in gastric cancers. Similar findings were observed in mouse models, suggesting that, while tuft cells are associated with precancerous pathologies, their loss is most associated with the progression to invasive cancer.

Targeting epidermal growth factor receptor to recruit newly generated neuroblasts in cortical brain injuries

BACKGROUND

Neurogenesis is stimulated in the subventricular zone (SVZ) of mice with cortical brain injuries. In most of these injuries, newly generated neuroblasts attempt to migrate toward the injury, accumulating within the corpus callosum not reaching the perilesional area.

METHODS

We use a murine model of mechanical cortical brain injury, in which we perform unilateral cortical injuries in the primary motor cortex of adult male mice. We study neurogenesis in the SVZ and perilesional area at 7 and 14 dpi as well as the expression and concentration of the signaling molecule transforming growth factor alpha (TGF-α) and its receptor the epidermal growth factor (EGFR). We use the EGFR inhibitor Afatinib to promote neurogenesis in brain injuries.

RESULTS

We show that microglial cells that emerge within the injured area and the SVZ in response to the injury express high levels of TGF-α leading to elevated concentrations of TGF-α in the cerebrospinal fluid. Thus, the number of neuroblasts in the SVZ increases in response to the injury, a large number of these neuroblasts remain immature and proliferate expressing the epidermal growth factor receptor (EGFR) and the proliferation marker Ki67. Restraining TGF-α release with a classical protein kinase C inhibitor reduces the number of these proliferative EGFR+ immature neuroblasts in the SVZ. In accordance, the inhibition of the TGF-α receptor, EGFR promotes migration of neuroblasts toward the injury leading to an elevated number of neuroblasts within the perilesional area.

CONCLUSIONS

Our results indicate that in response to an injury, microglial cells activated within the injury and the SVZ release TGF-α, activating the EGFR present in the neuroblasts membrane inducing their proliferation, delaying maturation and negatively regulating migration. The inactivation of this signaling pathway stimulates neuroblast migration toward the injury and enhances the quantity of neuroblasts within the injured area. These results suggest that these proteins may be used as target molecules to regenerate brain injuries.

EP300 facilitates human trophoblast stem cell differentiation

Early placenta development involves cytotrophoblast differentiation into extravillous trophoblast (EVT) and syncytiotrophoblast (STB). Defective trophoblast development and function may result in severe pregnancy complications, including fetal growth restriction and pre-eclampsia. The incidence of these complications is increased in pregnancies of fetuses affected by Rubinstein-Taybi syndrome, a developmental disorder predominantly caused by heterozygous mutations in CREB-binding protein (CREBBP) or E1A-binding protein p300 (EP300). Although the acetyltransferases CREBBP and EP300 are paralogs with many overlapping functions, the increased incidence of pregnancy complications is specific for EP300 mutations. We hypothesized that these complications have their origin in early placentation and that EP300 is involved in that process. Therefore, we investigated the role of EP300 and CREBBP in trophoblast differentiation, using human trophoblast stem cells (TSCs) and trophoblast organoids. We found that pharmacological CREBBP/EP300 inhibition blocks differentiation of TSCs into both EVT and STB lineages, and results in an expansion of TSC-like cells under differentiation-inducing conditions. Specific targeting by RNA interference or CRISPR/Cas9-mediated mutagenesis demonstrated that knockdown of EP300 but not CREBBP, inhibits trophoblast differentiation, consistent with the complications seen in Rubinstein-Taybi syndrome pregnancies. By transcriptome sequencing, we identified transforming growth factor alpha (TGFA, encoding TGF-α) as being strongly upregulated upon EP300 knockdown. Moreover, supplementing differentiation medium with TGF-α, which is a ligand for the epidermal growth factor receptor (EGFR), likewise affected trophoblast differentiation and resulted in increased TSC-like cell proliferation. These findings suggest that EP300 facilitates trophoblast differentiation by interfering with at least EGFR signaling, pointing towards a crucial role for EP300 in early human placentation.

Clinicopathological features and immunophenotype of Silva pattern system in endocervical adenocarcinoma

The aim of this study was to investigate the correlation between Silva pattern system and clinicopathological features of endocervical adenocarcinoma. Moreover, it was to find molecular markers helpful for Silva classification, and thus we also explored the expression levels of invasion, adhesion and proliferation biomarkers in cases of Silva non-invasive and invasive types. The survival based on Silva pattern system was analysed by Kaplan-Meier survival analysis, Log-rank test and  a COX risk proportionality model. Sixty samples were chosen to detect the MMP-2, MMP-9, u-PA, E-cadherin, β-catenin, EGF, TGF-α, HDGF, c-Met and RGN expression by immunohistochemistry. Multivariate analysis showed that pattern A/pattern B/pattern C Silva pattern system provided independent risk factors for prognosis. Our results found the levels of MMP-2, MMP-9 and u-PA were significantly higher in endocervical adenocarcinoma with destructive growth than in the  nondestructive group. The levels of E-cadherin and β-catenin were significantly lower in endocervical adenocarcinoma with destructive growth than in the nondestructive group. The levels of EGF, TGF-α and HDGF were significantly higher in endocervical adenocarcinoma with destructive growth than in the nondestructive group. Compared with 'non-invasive/invasive Silva pattern', this study suggests 'pattern A/pattern B/pattern C Silva pattern' could be a better criteria for predicting the prognosis. Furthermore, the dual-marker combination of 'MMP-2 and u-PA' and 'E-cadherin and β-catenin' is very important in the diagnosis of Silva pattern classification.

Low-dose arsenite causes overexpression of EGF, TGFα, and HSP90 through Trx1-TXNIP-NLRP3 axis mediated signaling pathways in the human bladder epithelial cells

Epidemiological studies have demonstrated an increased incidence of bladder cancer in arseniasis- endemic areas; however, the precise molecular mechanisms remain unknown. Our previous results have shown that the protein levels of EGF, TGFα, and HSP90 in arsenite-treated bladder uroepithelial cells increased markedly and contributed to hyperactivation of EGF receptors. The aim of this study was to further explore the regulatory ways underlying overexpression of EGF, TGFα, and HSP90 in these cells. The present results showed that both Trx and GSH systems were stimulated in arsenite-treated cells, and ROS levels in 2 μM arsenite-treated cells did not changed obviously; however, ROS levels in 4 μM arsenite-treated cells increased significantly. By using the antioxidant and specific inhibitors, we found that in 2 μM arsenite-treated cells, JNK/NF-κB signaling pathway was involved in overexpression of EGF and TGFα, and ERK/NF-κB signaling pathway contributed to HSP90 overexpression, however in 4 μM arsenite-treated cells, both ERK/ and JNK/NF-κB signaling pathways were involved in overexpression of EGF, TGFα, and HSP90, and PI3K/AKT/NF-κB signaling pathway contributed to overexpression of EGF and TGFα. Furthermore, our results also showed that the Trx1-TXNIP-NLRP3 axis was activated in arsenite-treated cells, and played a pivotal role in activation of the signaling pathways involved in overexpression of EGF, TGFα, and HSP90. In conclusion, the Trx1-TXNIP-NLRP3 axis might be activated by arsenite-induced redox imbalance in bladder uroepithelial cells, and mediate the activation of signaling pathways involved in overexpression of EGF, TGFα, and HSP90.

Clenbuterol attenuates immune reaction to lipopolysaccharide and its relationship to anhedonia in adolescents

While inflammation has been implicated in psychopathology, relationships between immune-suppressing processes and psychiatric constructs remain elusive. This study sought to assess whether β2-agonist clenbuterol (CBL) would attenuate immune activation in adolescents with mood and anxiety symptoms following ex vivo exposure of whole blood to lipopolysaccharide (LPS). Our focus on adolescents aimed to target a critical developmental period when psychiatric conditions often emerge and prior to chronicity effects. To capture a diverse range of immunologic and symptomatologic phenotypes, we included 97 psychotropic-medication free adolescents with mood and anxiety symptoms and 33 healthy controls. All participants had comprehensive evaluations and dimensional assessments of psychiatric symptoms. Fasting whole-blood samples were collected and stimulated with LPS in the presence and absence of CBL for 6 hours, then analyzed for 41 cytokines, chemokines, and hematopoietic growth factors. Comparison analyses used Bonferroni-corrected nonparametric tests. Levels of nine immune biomarkers-including IL-1RA, IL-1β, IL-6, IP-10, MCP-1, MIP-1α, MIP-1β, TGF-α, and TNF-α-were significantly reduced by CBL treatment compared to LPS alone. Exploratory factor analysis reduced 41 analytes into 5 immune factors in each experimental condition, and their relationships with psychiatric symptoms were examined as a secondary aim. CBL + LPS Factor 4-comprising EGF, PDGF-AA, PDGF-AB/BB, sCD40L, and GRO-significantly correlated with anticipatory and consummatory anhedonia, even after controlling for depression severity. This study supports the possible inhibitory effect of CBL on immune activation. Using a data-driven method, distinctive relationships between CBL-affected immune biomarkers and dimensional anhedonia were reported, further elucidating the role of β2-agonism in adolescent affective symptomatology.

Blockade of EGFR Activation Promotes TNF-Induced Lung Epithelial Cell Apoptosis and Pulmonary Injury

Pneumonitis is the leading cause of death associated with the use of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) against non-small cell lung cancer (NSCLC). However, the risk factors and the mechanism underlying this toxicity have not been elucidated. Tumor necrosis factor (TNF) has been reported to transactivate EGFR in pulmonary epithelial cells. Hence, we aimed to test the hypothesis that EGFR tyrosine kinase activity regulates TNF-mediated bronchial epithelial cell survival, and that inhibition of EGFR activity increases TNF-induced lung epithelial cell apoptosis. We used surfactant protein C (SPC)-TNF transgenic (tg) mice which overexpress TNF in the lungs. In this model, gefitinib, an EGFR-TKI, enhanced lung epithelial cell apoptosis and lymphocytic inflammation, indicating that EGFR tyrosine kinase prevents TNF-induced lung injury. Furthermore, IL-17A was significantly upregulated by gefitinib in SPC-TNF tg mice and p38MAPK activation was observed, indicative of a pathway involved in lung epithelial cell apoptosis. Moreover, in lung epithelial cells, BEAS-2B, TNF stimulated EGFR transactivation via the TNF-α-converting enzyme in a manner that requires heparin binding (HB)-EGF and transforming growth factor (TGF)-α. These novel findings have significant implications in understanding the role of EGFR in maintaining human bronchial epithelial cell homeostasis and in NSCLC treatment.

[Effect of local injection of rhTGF-α1 on osteoclasts during orthodontic tooth movement in rats]

PURPOSE

To investigate the effect of exogenous TGF-β1 on improving periodontal tissues remodeling during orthodontic tooth movement in rats.

METHODS

Eighty male SD rats were randomly divided into 2 groups. Rats in the experimental group were injected respectively with rhTGF-β1 in dosages of 0.1 mL (5 ng/mL) in the buccal submucosal area of the molar every other day, while rats in the control group received equivalent volumes of PBS. Each group (n=40) was subdivided equally into 5 subgroups. An orthodontic appliance, consisting of a 5 mm nickel titanium closed coil spring, was ligated between the maxillary left incisor and first molar of each rat to deliver an initial force of 0.49N. Eight rats in each subgroup were sacrificed at one of the five time points (1, 4, 7, 10 and 14 days) after appliance placement. The distance of the tooth movement was measured by using stereomicroscope. Tissue sections around the first maxillary left molar were stained with tartrate-resistant acid phosphatase (TRAP) histochemistry to analyze the changes of the amount and distribution of osteoclasts on the compression side of tooth. Statistical analysis was performed using SPSS 17.0 software package.

RESULTS

Molars treated with rhTGF-β1 moved mesially more rapidly than the control group. The distance of tooth movement of the experimental group showed a significant increase compared with the control group at day 7 (P<0.05) and significant increase compared with the control group at day 10 and 14 (P<0.01). The number of TRAP positive cells appearing in the periodontal ligament space on the pressure side of the alveolar bone were increased markedly in experimental group. There were statistically significant differences in the amount of osteoclasts between experimental and control groups (P<0.01).

CONCLUSIONS

Local injection of rhTGF-β1 in the periodontal tissues can accelerate orthodontic tooth movement via enhancing the numbers of osteoclasts. At the histologic level, increased numbers of mononuclear osteoclasts are recruited and activated, resulting in greater amounts of alveolar bone resorption on the pressure side of the periodontal ligament.

[Expression and regulation of tight junction protein Occludin in nasal polyps]

OBJECTIVE

To evaluate the possible role of tight junction protein Occludin in nasal polyps.

METHODS

The expression of Claudin-1, Occludin and ZO-1 in nasal polyps (n = 20) and healthy uncinate mucosa (n = 15) were examined using immunohistochemical staining, real-time quantitative polymerase chain reaction (PCR) and Western blot analysis. The regulatory effects of proinflammatory cytokines (IFN-γ, IL-13, IL-17, TGF-β, TGF-α) on the expression of Occludin in cultured human nasal epithelial cells were investigated.

RESULTS

The immunohistochemical results showed that Claudin-1, Occludin and ZO-1 were detected both in the nasal polyp group and the control group. The expression sites were the cell membrane and cytoplasm of nasal mucosa epithelial cells. The mean optical density of Claudin-1, Occludin and ZO-1 were 0.187 ± 0.076,0.172 ± 0.109 and 0.098 ± 0.035 respectively in the nasal polyp group and were significantly lower than those in the control group (0.312 ± 0.101, 0.220 ± 0.069 and 0.233 ± 0.093 respectively), the differences were significant (t = 9.345, t = 3.301, t = 13.323, all P < 0.01).RT-PCR results showed that the relative expression of Occludin mRNA was 0.000 117 ± 0.000 035 in the nasal polyp group and was significantly lower than that in the control group(0.000 464 ± 0.000 134), and the difference was significant (Z = -5.0, P < 0.01) . There was no statistically significant difference in the relative expression of Claudin-1 and ZO-1 mRNA between the nasal polyp group and the control group (P > 0.05) . After the cultured human nasal epithelial cells were stimulated by IL-13, IL-17, IFN-γ and other proinflammatory cytokines, the relative expression of Occludin mRNA was 0.631 ± 0.039, 0.581 ± 0.029 and 0.648 ± 0.040, respectively. Compared with the unstimulated control group, the differences were statistically significant (t = 16.299, 24.669 and 14.995 respectively, all P < 0.05).Western blot analyse showed that the relative grayscale in the above proinflammatory cytokines stimulation groups was 0.650 ± 0.061,0.482 ± 0.106 and 0.536 ± 0.109, respectively. Compared with the unstimulated control group, the differences were statistically significant (t = 9.880, 8.442 and 7.310 respectively, all P < 0.05).

CONCLUSIONS

The reduced expression of Occludin might be involved in the pathogenesis of nasal polyps.

Protein kinase C iota regulates pancreatic acinar-to-ductal metaplasia

Pancreatic acinar-to-ductal metaplasia (ADM) is associated with an increased risk of pancreatic cancer and is considered a precursor of pancreatic ductal adenocarcinoma. Transgenic expression of transforming growth factor alpha (TGF-α) or K-ras^G12D in mouse pancreatic epithelium induces ADM in vivo. Protein kinase C iota (PKCι) is highly expressed in human pancreatic cancer and is required for the transformed growth and tumorigenesis of pancreatic cancer cells. In this study, PKCι expression was assessed in a mouse model of K-ras^G12D-induced pancreatic ADM and pancreatic cancer. The ability of K-ras^G12D to induce pancreatic ADM in explant culture, and the requirement for PKCι, was investigated. PKCι is elevated in human and mouse pancreatic ADM and intraepithelial neoplastic lesions in vivo. We demonstrate that K-ras^G12D is sufficient to induce pancreatic ADM in explant culture, exhibiting many of the same morphologic and biochemical alterations observed in TGF-α-induced ADM, including a dependence on Notch activation. PKCι is highly expressed in both TGF-α- and K-ras^G12D-induced pancreatic ADM and inhibition of PKCι significantly reduces TGF-α- and K-ras^G12D-mediated ADM. Inhibition of PKCι suppresses K-ras^G12D–induced MMP-7 expression and Notch activation, and exogenous MMP-7 restores K-ras^G12D–mediated ADM in PKCι-depleted cells, implicating a K-ras^G12D-PKCι-MMP-7 signaling axis that likely induces ADM through Notch activation. Our results indicate that PKCι is an early marker of pancreatic neoplasia and suggest that PKCι is a potential downstream target of K-ras^G12D in pancreatic ductal metaplasia in vivo.

[Instability of cell phenotype and tumor initiating cells in gliomas]

Gliomas, the most frequent primitive CNS tumors, have been suggested to originate from astrocytes or from neural progenitors/stem cells. However, the precise identity of the cells at the origin of gliomas remains a matter of debate because no pre-neoplastic state has been yet identified. TGFα, an EGF family member, is frequently over-expressed in the early stages of glioma progression. We questioned whether prolonged TGFα exposure affects the stability of the normal mature astrocyte phenotype and, eventually, their propensity to cancerous transformation. Using mouse astrocyte cultures devoid of residual neural stem cells or progenitors, we demonstrate that several days of TGFα-treatment result in the functional conversion of a population of mature astrocytes into radial glial cells, a population of neural progenitors, without any accompanying sign of cancerous transformation. In contrast, when astrocytes de-differentiated with TGFα were submitted to oncogenic stress using gamma irradiation, they acquired cancerous properties, forming high-grade glioma-like tumors after brain grafting. Gamma irradiation was without effect on astrocytes which were not treated with TGFα. These results suggested that most gliomas should contain tumor cells with stem-like properties (TSCs). Our study of 55 pediatric brain tumors show that tumor cells with stem cell-like or progenitor-like properties can be isolated from a majority of gliomas. Survival analysis showed an association between isolation of TSCs with extended self-renewal capabilities and a patient's higher mortality rate.

Fetuin-A promotes primary keratinocyte migration: independent of epidermal growth factor receptor signalling

Previously, we reported that fetuin-A is a major component of ovine foetal skin and significantly enhances 'wound closure' in primary keratinocyte cultures. In this study, we found that in human newborn foreskin, a high level of fetuin-A protein is detected throughout the dermis. However, in adult skin a low level of fetuin-A is observed throughout the epidermal and dermal layers, except at regions surrounding hair follicles and at the epidermal-dermal junction where the level of fetuin-A is relatively high. Fetuin-A significantly induces actin-rich protrusions in human primary keratinocytes. Interestingly, blockade of epidermal growth factor (EGF) receptor signalling has a limited effect on fetuin-A promoted 'wound closure' on primary human keratinocytes, but significantly inhibits fetuin-A's effect on HaCaT cells. These results indicate that high levels of fetuin-A may partially contribute to less scar formation in newborn foreskin and that the effect of fetuin-A on primary keratinocyte migration is independent of EGF receptor signalling.

Molecular and histological analysis of a new rat model of experimental knee osteoarthritis

Articular cartilage degeneration is the most consistently observed feature of osteoarthritis (OA). Animal and human studies have shown that various forms of exercise influence the course of the disease in different ways. In addition, early changes in articular cartilage that influence the progression of OA, such as the expression of cytokines, require further investigation. We have used a surgically induced experimental model of knee OA to address these questions. Here, we discuss our recent studies investigating the effects of an exercise paradigm in surgically induced OA, which determined that the destabilized knee joint is susceptible to enhanced degeneration when subjected to low-intensity, low-impact exercise. Further, we investigated early global changes in gene expression in articular chondrocytes from degenerating cartilage. Identified candidate genes including genes involved in chemokine, endothelin, and transforming growth factor-alpha signaling are discussed in the context of articular cartilage degeneration in early OA.

[Relationship between transforming growth factor-alpha gene polymorphism and non-syndromic cleft lip with cleft palate]

OBJECTIVE

To study the association of TGF-alpha gene polymorphism and non-syndromic cleft lip with cleft palate in Shandong province.

METHODS

Polymerase chain reaction combined with restrict enzyme digestion was used to detect the target gene variation in 98 patients with non-syndromic cleft lip with cleft palate and 101 healthy controls.

RESULTS

The C2 allele frequency in patients with non-syndromic cleft lip with cleft palate was significantly higher than that in healthy controls. The genotype frequency in patients with positive family history was significantly higher than that without positive family history.

CONCLUSION

TGF-alpha gene polymorphism is closely associated with non-syndromic cleft lip with cleft palate in Shandong, especially in patients with positive family history.

Conjugated linoleic acid inhibits peritoneal metastasis in human gastrointestinal cancer cells

The effect of conjugated linoleic acid (CLA) on peritoneal metastasis was examined by in vitro treatment of cancer cells and mouse peritoneal metastasis models. First, cell growth of MKN28 human gastric cancer cells and Colo320 human colon cancer cells was suppressed by CLA in a dose-dependent manner with an increment in apoptosis. CLA significantly inhibited invasion into type IV collagen-coated membrane of MKN28 and Colo320 cells (p < 0.05). CLA-induced growth inhibition was recovered by the exposure to antisense S-oligodeoxynucleotide for peroxisome proliferator-activated receptor (PPAR)-gamma in both cell lines. BALB/c nu-nu mice were inoculated with MKN28 and Colo320 cells into their peritoneal cavity, and administrated with CLA intraperitoneally (weekly, 4 times). CLA treatment did not affect food intake or weight gain of mice. CLA treatment significantly decreased metastatic foci of both cells in the peritoneal cavity (p < 0.005). Survival rate in mice inoculated with MKN28 or Colo320 cells was significantly recovered by CLA treatment (p = 0.0025 and 0.0052, respectively). Protein production in MKN28 and Colo320 cells treated with CLA showed a decrease in epidermal growth factor receptor and transforming growth factor-alpha and an increase in Bax. These findings suggest that CLA inhibits metastasis of human gastric and colon cancer cells.

The immunohistochemical approach to determine the origin and possible function of the juxtaoral organ in dogs

OBJECTIVE

In this study, we applied immuno- histochemical techniques on the functionally little known organ of Chievitz (juxtaoral organ [JOO]) in dogs to determine its origin and possible function.

METHODS

The term abortive materials of 6 Doberman dogs were used for experimental procedures in July 2002 to June 2003 at Gazi University Faculty of Medicine, Ankara, Turkey, after routine light microscopic tissue preparation, the sections were stained with Masson's trichrome stain. In order to elucidate the function-related origin of the organ, we used epidermal growth factor (EGF-r), transforming growth factor (TGF-alpha) and nerve growth factor (NGF-beta) immunohistochemical stains.

RESULTS

We observed a very strong and widespread immunoreactivity of EGF-r and TGF-alpha on simple squamous capsular cells. We detected nerve growth factor-beta positivity in granular form both in simple squamous capsular cells and in neighboring connective tissue. However, we did not detect EGF-r reactivity on parenchymal cells except a weak immunoreactivity on central ones. We noticed transforming growth factor-alpha in most of the parenchymal cells while we observed NGF-beta strongly in all the parenchymal cells.

CONCLUSION

These results may point out that the JOO may be of mesothelial or epithelial origin. Having NGF-alpha positive granules and close relationship with blood vessels may imply a neurosecretory function. We believe that our study may add new perspectives to the function of the JOO.

Synergistic effects of combination therapy employing antisense oligonucleotides with traditional chemotherapeutics in the PC-3 prostate cancer model

Combination therapy including antisense oligonucleotides (ODNs) with traditional chemotherapeutic agents offers potential benefits by increasing the effectiveness of the chemotherapeutics, reducing their effective dosage, and simultaneously reducing toxicity. Previously we have reported that antisense ODNs specific for transforming growth factor-alpha (TGF-alpha) and its binding site, the epidermal growth factor receptor (EGFR) (MR1 and MR2, respectively), are effective against the PC-3 in vitro and in vivo prostate cancer models. In this series we evaluated these antisense ODNs in various combinations and treatment cycles with paclitaxel (Taxol), cyclophosphamide (Cytoxan), mitoxantrone, carboplatin, cisplatin, and oxaliplatin in order to identify synergistic effects.We found that when either of the ODNs were simultaneously administered with Taxol, no synergistic activity was noted. However, when sequentially administered in a series 1 d apart, a pretreatment with the ODN directed against TGF-alpha (6.64 microm) followed by Taxol (5 nm) had significantly (p <0.001) greater activity than these agents similarly administered in the reverse order or simultaneously. When Cytoxan was administered in sequence with both ODNs significantly increased growth inhibition was obtained compared to when Cytoxan was administered alone. A 1 d treatment of PC-3 cells with Cytoxan followed the next day with MR1 was significantly more effective (p <0.0001). The reverse order, a pretreatment with MR1 followed by Cytoxan, also resulted in significant additional inhibition (p=0.0004). Similarly sequenced, MR2 followed by Cytoxan, was also significantly more effective (p=0.0014) than Cytoxan treatment alone. For mitoxantrone, which was administered in combination therapy with ODNs: mitoxantrone with MR1 was significantly more inhibitory than the combination of both MR1 and MR2 ODNs (p=0.006) and also mitoxantrone administered alone (p=0.0012). Mitoxantrone administered with MR1 was not significantly different from mitoxantrone given in combination with MR2. Although mitoxantrone and MR2 was statistically (p=00015) more inhibitory than mitoxantrone alone, this combination was barely more effective (p=0.04) than the MR1 ODN administered alone.

Drosophila gurken (TGFalpha) mRNA localizes as particles that move within the oocyte in two dynein-dependent steps

In Drosophila oocytes, gurken mRNA localization orientates the TGF-alpha signal to establish the anteroposterior and dorsoventral axes. We have elucidated the path and mechanism of gurken mRNA localization by time-lapse cinematography of injected fluorescent transcripts in living oocytes. gurken RNA assembles into particles that move in two distinct steps, both requiring microtubules and cytoplasmic Dynein. gurken particles first move toward the anterior and then turn and move dorsally toward the oocyte nucleus. We present evidence suggesting that the two steps of gurken RNA transport occur on distinct arrays of microtubules. Such distinct microtubule networks could provide a general mechanism for one motor to transport different cargos to distinct subcellular destinations.

CSN5/Jab1 mutations affect axis formation in theDrosophila oocyte by activating a meiotic checkpoint

The COP9 signalosome (CSN) is linked to signaling pathways and ubiquitin-dependent protein degradation in yeast, plant and mammalian cells,but its roles in Drosophila development are just beginning to be understood. We show that during oogenesis CSN5/JAB1, one subunit of the CSN,is required for meiotic progression and for establishment of both the AP and DV axes of the Drosophila oocyte. The EGFR ligand Gurken is essential for both axes, and our results show that CSN5 mutations block the accumulation of Gurken protein in the oocyte. CSN5 mutations also cause the modification of Vasa, which is known to be required for Gurken translation. This CSN5 phenotype — defective axis formation, reduced Gurken accumulation and modification of Vasa — is very similar to the phenotype of the spindle-class genes that are required for the repair of meiotic recombination-induced, DNA double-strand breaks. When these breaks are not repaired, a DNA damage checkpoint mediated by mei-41 is activated. Accordingly, the CSN5 phenotype is suppressed by mutations inmei-41 or by mutations in mei-W68, which is required for double strand break formation. These results suggest that, like thespindle-class genes, CSN5 regulates axis formation by checkpoint-dependent, translational control of Gurken. They also reveal a link between DNA repair, axis formation and the COP9 signalosome, a protein complex that acts in multiple signaling pathways by regulating protein stability.

Weight-cycling decreases incidence and increases latency of mammary tumors to a greater extent than does chronic caloric restriction in mouse mammary tumor virus-transforming growth factor-alpha female mice

Multiple periods of caloric restriction (or fasting)/refeeding in rodents have had inconsistent effects on mammary tumor (MT) development. In the present study, the consequence of intermittent caloric restriction/refeeding resulting in weight-cycling was evaluated using an oncogene-induced MT mouse model. Hybrid mouse MT virus-transforming growth factor alpha (MMTV-TGF-alpha)/Lep(+)Lep(ob) female mice were used. Ad libitum-fed mice (n = 30) were fed American Institute of Nutrition (AIN)-93M diet. Beginning at 10 weeks of age, weight-cycled mice (n = 30) were fed an AIN-93 modified diet (2-fold increase in protein, fat, vitamin, and mineral contents) at 50% of ad libitum for 3-week intervals followed by 3-week intervals of ad libitum feeding using AIN-93M diet. Pair-fed mice (n = 33), were fed a 2:1 mixture of AIN-93M:AIN-93 modified diets to match the caloric intake of weight-cycled mice for each 6-week age-matched caloric restriction/refeeding interval. Food intakes were determined daily and body weights weekly. Mice were euthanized when MTs exceeded 20 mm in length or at 80 weeks of age. Final body weights were similar, but cumulative food intake of ad libitum-fed mice was 21% greater than that of the other groups. Ad libitum-fed mice had a 77% MT incidence versus 3% for weight-cycled and 44% for pair-fed mice. MTs were detected earlier for ad libitum-fed mice, 64.1 weeks versus 73.5 weeks for pair-fed mice. The only MT in one weight-cycled mouse was excised at necropsy (80 weeks of age) and weighed only 0.063 g. Average MT weight for ad libitum-fed mice was 1.034 g and for pair-fed mice was 0.667 g. Intervals of caloric restriction/refeeding resulting in weight-cycling were protective against MT development in this mouse model. Future studies should address the application of this intervention to additional transgenic mice as well as other MT models.

A family of Rhomboid intramembrane proteases activates all Drosophila membrane-tethered EGF ligands

Drosophila has three membrane-tethered epidermal growth factor (EGF)-like proteins: Spitz, Gurken and Keren. Spitz and Gurken have been genetically confirmed to activate the EGF receptor, but Keren is uncharacterized. Spitz is activated by regulated intracellular translocation and cleavage by the transmembrane proteins Star and the protease Rhomboid-1, respectively. Rhomboid-1 is a member of a family of seven similar proteins in Drosophila. We have analysed four of these: all are proteases that can cleave Spitz, Gurken and Keren, and all activate only EGF receptor signalling in vivo. Star acts as an endoplasmic reticulum (ER) export factor for all three. The importance of this translocation is highlighted by the fact that when Spitz is cleaved by Rhomboids in the ER it cannot be secreted. Keren activates the EGF receptor in vivo, providing strong evidence that it is a true ligand. Our data demonstrate that all membrane-tethered EGF ligands in Drosophila are activated by the same strategy of cleavage by Rhomboids, which are ancient and widespread intramembrane proteases. This is distinct from the metalloprotease-induced activation of mammalian EGF-like ligands.

Mechanisms of Gurken-dependentpiperegulation and the robustness of dorsoventral patterning inDrosophila

The restriction of Pipe, a potential glycosaminoglycan-modifying enzyme, to ventral follicle cells of the egg chamber is essential for dorsoventral axis formation in the Drosophila embryo. pipe repression depends on the TGFα-like ligand Gurken, which activates the Drosophila EGF receptor in dorsal follicle cells. An analysis of Raf mutant clones shows that EGF signalling is required cell-autonomously in all dorsal follicle cells along the anteroposterior axis of the egg chamber to repress pipe. However, the autoactivation of EGF signalling important for dorsal follicle cell patterning has no influence on pipe expression. Clonal analysis shows that also the mirror-fringe cassette suggested to establish a secondary signalling centre in the follicular epithelium is not involved in pipe regulation. These findings support the view that the pipe domain is directly delimited by a long-range Gurken gradient. Pipe induces ventral cell fates in the embryo via activation of the Spätzle/Toll pathway. However, large dorsal patches of ectopic pipe expression induced by Raf clones rarely affect embryonic patterning if they are separated from the endogenous pipe domain. This indicates that potent inhibitory processes prevent pipe dependent Toll activation at the dorsal side of the egg.

Desensitization of cannabinoid-mediated presynaptic inhibition of neurotransmission between rat hippocampal neurons in culture

Prolonged exposure to cannabinoids results in tolerance in vivo and desensitization of cannabinoid receptors in vitro. We show here that cannabinoid-induced presynaptic inhibition of glutamatergic neurotransmission desensitized after prolonged exposure to the cannabinoid receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl](1-napthalenyl)methanone monomethanesulfonate (Win55,212-2). Synaptic activity between hippocampal neurons in culture was determined from network-driven increases in intracellular Ca(2+) concentration ([Ca(2+)](i) spikes) and excitatory postsynaptic currents. Win55,212-2-induced (100 nM) inhibition partially desensitized after 2 h and completely desensitized after 18- to 24-h exposure. The desensitization could be overcome by higher concentrations of agonist as indicated by a parallel rightward shift of the concentration response curve from an EC(50) of 2.7 +/- 0.3 nM to 320 +/- 147 nM for inhibition of [Ca(2+)](i) spiking and from 43 +/- 17 nM to 4505 +/- 403 nM for inhibition of synaptic currents, suggesting that this phenomenon may underlie tolerance. Presynaptic expression of dominant negative G-protein-coupled-receptor kinase (GRK2-Lys220Arg) or beta-arrestin (319-418) reduced the desensitization produced by 18- to 24-h pretreatment with 100 nM, Win55,212-2 suggesting that desensitization followed the prototypical pathway for G-protein-coupled receptors. Prolonged treatment with Win55,212-2 produced a modest increase in the EC(50) for adenosine inhibition of synaptic transmission and pretreatment with cyclopentyladenosine produced a slight increase in the EC(50) for Win55,212-2, suggesting a reciprocal ability to produce heterologous desensitization. The long-term changes in synaptic function that accompany chronic cannabinoid exposure will be an important factor in evaluating the therapeutic potential of these drugs and will provide insight into the role of the endocannabinoid system.

Mechanism of activation of theDrosophilaEGF Receptor by the TGFα ligand Gurken during oogenesis

We have analyzed the mechanism of activation of the Epidermal growth factor receptor (Egfr) by the transforming growth factor (TGF) α-like molecule, Gurken (Grk). Grk is expressed in the oocyte and activates the Egfr in the surrounding follicle cells during oogenesis. We show that expression of either a membrane bound form of Grk (mbGrk), or a secreted form of Grk (secGrk), in either the follicle cells or in the germline, activates the Egfr. In tissue culture cells, both forms can bind to the Egfr; however, only the soluble form can trigger Egfr signaling, which is consistent with the observed cleavage of Grk in vivo. We find that the two transmembrane proteins Star and Brho potentiate the activity of mbGrk. These two proteins collaborate to promote an activating proteolytic cleavage and release of Grk. After cleavage, the extracellular domain of Grk is secreted from the oocyte to activate the Egfr in the follicular epithelium.

The Drosophila RGS protein Loco is required for dorsal/ventral axis formation of the egg and embryo, and nurse cell dumping

The loco gene encodes members of a family of RGS proteins responsible for the negative regulation of G-protein signalling. At least two transcripts of loco are expressed in oogenesis, loco-c2 is observed in the anterior-dorsal follicle cells and is downstream of the epidermal growth factor receptor signalling pathway, initiated in the oocyte. loco-c3 is a new transcript of loco, which is expressed in the nurse cells from stage 6 onwards. Analysis of newly generated mutants and antisense technology enabled us to establish that disrupting loco in follicle cells results in ventralized eggs, while disrupting loco in nurse cells results in short eggs, due to defective dumping of the nurse cell cytoplasm into the oocyte.

Drosophila rhino encodes a female-specific chromo-domain protein that affects chromosome structure and egg polarity

Here we describe our analyses of Rhino, a novel member of the Heterochromatin Protein 1(HP1) subfamily of chromo box proteins. rhino (rhi) is expressed only in females and chiefly in the germline, thus providing a new tool to dissect the role of chromo-domain proteins in development. Mutations in rhi disrupt eggshell and embryonic patterning and arrest nurse cell nuclei during a stage-specific reorganization of their polyploid chromosomes, a mitotic-like state called the "five-blob" stage. These visible alterations in chromosome structure do not affect polarity by altering transcription of key patterning genes. Expression levels of gurken (grk), oskar (osk), bicoid (bcd), and decapentaplegic (dpp) transcripts are normal, with a slight delay in the appearance of bcd and dpp mRNAs. Mislocalization of grk and osk transcripts, however, suggests a defect in the microtubule reorganization that occurs during the middle stages of oogenesis and determines axial polarity. This defect likely results from aberrant Grk/Egfr signaling at earlier stages, since rhi mutations delay synthesis of Grk protein in germaria and early egg chambers. In addition, Grk protein accumulates in large, actin-caged vesicles near the endoplasmic reticulum of stages 6-10 egg chambers. We propose two hypotheses to explain these results. First, Rhi may play dual roles in oogenesis, independently regulating chromosome compaction in nurse cells at the end of the unique endoreplication cycle 5 and repressing transcription of genes that inhibit Grk synthesis. Thus, loss-of-function mutations arrest nurse cell chromosome reorganization at the five-blob stage and delay production or processing of Grk protein, leading to axial patterning defects. Second, Rhi may regulate chromosome compaction in both nurse cells and oocyte. Loss-of-function mutations block nurse cell nuclear transitions at the five-blob stage and activate checkpoint controls in the oocyte that arrest Grk synthesis and/or inhibit cytoskeletal functions. These functions may involve direct binding of Rhi to chromosomes or may involve indirect effects on pathways controlling these processes.

Stable anterior anchoring of the oocyte nucleus is required to establish dorsoventral polarity of the Drosophila egg

In Drosophila, dorsoventral polarity is established by the asymmetric positioning of the oocyte nucleus. In egg chambers mutant for cap 'n' collar, the oocyte nucleus migrates correctly from a posterior to an anterior-dorsal position where it remains during stage 9 of oogenesis. However, at the end of stage 9, the nucleus leaves its anterior position and migrates towards the posterior pole. The mislocalisation of the nucleus is accompanied by changes in the microtubule network and a failure to maintain bicoid and oskar mRNAs at the anterior and posterior poles, respectively. gurken mRNA associates with the oocyte nucleus in cap 'n' collar mutants and initially the local secretion of Gurken protein activates the Drosophila EGF receptor in the overlying dorsal follicle cells. However, despite the presence of spatially correct Grk signalling during stage 9, eggs laid by cap 'n' collar females lack dorsoventral polarity. cap 'n' collar mutants, therefore, allow for the study of the influence of Grk signal duration on DV patterning in the follicular epithelium.

A nuclear lamin is required for cytoplasmic organization and egg polarity in Drosophila

Nuclear lamins are intermediate filaments that compose the nuclear lamina--the filamentous meshwork underlying the inner nuclear membrane--and are required for nuclear assembly, organization and maintenance. Here we present evidence that a nuclear lamin is also required for cytoplasmic organization in two highly polarized cell types. Zygotic loss-of-function mutations in the Drosophila gene encoding the principal lamin (Dm(0)) disrupt the directed outgrowth of cytoplasmic extensions from terminal cells of the tracheal system. Germline mutant clones disrupt dorsal-ventral polarity of the oocyte. In mutant oocytes, transcripts of the dorsal determinant Gurken, a transforming growth factor-alpha homologue, fail to localize properly around the anterodorsal surface of the oocyte nucleus; their ventral spread results in dorsalized eggs that resemble those of the classical dorsalizing mutations squid and fs(1)K10. The requirement of a nuclear lamin for cytoplasmic as well as nuclear organization has important implications for both the cellular functions of lamins and the pathogenesis of human diseases caused by lamin mutations.

Functioning of the Drosophila orb gene in gurken mRNA localization and translation

The orb gene encodes an RNA recognition motif (RRM)-type RNA-binding protein that is a member of the cytoplasmic polyadenylation element binding protein (CPEB) family of translational regulators. Early in oogenesis, orb is required for the formation and initial differentiation of the egg chamber, while later in oogenesis it functions in the determination of the dorsoventral (DV) and anteroposterior axes of egg and embryo. In the studies reported here, we have examined the role of theorb gene in the gurken (grk)-Drosophila epidermal growth factor receptor (DER) signaling pathway. During the previtellogenic stages of oogenesis, the grk-DER signaling pathway defines the posterior pole of the oocyte by specifying posterior follicle cell identity. This is accomplished through the localized expression of Grk at the very posterior of the oocyte. Later in oogenesis, thegrk-DER pathway is used to establish the DV axis. Grk protein synthesized at the dorsal anterior corner of the oocyte signals dorsal fate to the overlying follicle cell epithelium. We show that orb functions in both the early and late grk-DER signaling pathways, and in each case is required for the localized expression of Grk protein. We have found thatorb is also required to promote the synthesis of a key component of the DV polarity pathway, K(10). Finally, we present evidence that Orb protein expression during the mid- to late stages of oogenesis is, in turn, negatively regulated by K(10).

Axis formation during Drosophila oogenesis

Recent advances shed light on the cellular processes that cooperate during oogenesis to produce a fully patterned egg, containing all the maternal information required for embryonic development. Progress has been made in defining the early steps in oocyte specification and it has been shown that progression of oogenesis is controlled by a meiotic checkpoint and requires active maintenance of the oocyte cell fate. The function of Gurken signalling in patterning the dorsal-ventral axis later in oogenesis is better understood. Anterior-posterior patterning of the embryo requires activities of bicoid and oskar mRNAs, localised within the oocyte. A microtubule motor, Kinesin, is directly implicated in localisation of oskar mRNA to the posterior pole of the oocyte.

Spätzle regulates the shape of the Dorsal gradient in the Drosophila embryo

Dorsal-ventral polarity of the Drosophila embryo is established by a nuclear gradient of Dorsal protein, generated by successive gurken-Egfr and spätzle-Toll signaling. Overexpression of extracellular Spätzle dramatically reshapes the Dorsal gradient: the normal single peak is broadened and then refined to two distinct peaks of nuclear Dorsal, to produce two ventral furrows. This partial axis duplication, which mimics the ventralized phenotype caused by reduced gurken-Egfr signaling, arises from events in the perivitelline fluid of the embryo and occurs at the level of Spätzle processing or Toll activation. The production of two Dorsal peaks is addressed by a model that invokes action of a diffusible inhibitor, which is proposed to normally regulate the slope of the Dorsal gradient.

Delta signaling from the germ line controls the proliferation and differentiation of the somatic follicle cells during Drosophila oogenesis

The body axes of Drosophila are established during oogenesis through reciprocal interactions between the germ line cells and the somatic follicle cells that surround them. The Notch pathway is required at two stages in this process: first, for the migration of the follicle cells around the germ line cyst and, later, for the polarization of the anterior-posterior (A-P) axis of the oocyte. Its function in these events, however, has remained controversial. Using clonal analysis, we show that Notch signaling controls cell proliferation and differentiation in the whole follicular epithelium. Notch mutant follicle cells remain in a precursor state and fail to switch from the mitotic cell cycle to the endocycle. Furthermore, removal of Delta from the germ line produces an identical phenotype, showing that Delta signals from the germ cells to control the timing of follicle cell differentiation. This explains the axis formation defects in Notch mutants, which arise because undifferentiated posterior follicle cells cannot signal to polarize the oocyte. Delta also signals from the germ line to Notch in the soma earlier in oogenesis to control the differentiation of the polar and stalk follicle cells. The germ line therefore regulates the development of the follicle cells through two complementary signaling pathways: Gurken signals twice to control spatial patterning, whereas Delta signals twice to exert temporal control.

RNA localization and translational regulation during axis specification in the Drosophila oocyte

The major axes of the oocyte-antero-posterior and dorso-ventral-are established over a one-day period during mid-oogenesis in Drosophila. The same molecule, GURKEN (GRK), functions to initiate signaling between the oocyte and the surrounding, somatically derived follicle cells. This results first in specification of the antero-posterior axis and, later, the dorso-ventral axis of the oocyte and surrounding follicle cells. Central to specification of both axes is a combination of cytoplasmic localization and translational regulation of the grk RNA. Here we discuss the mechanisms by which the grk RNA is localized within the oocyte and the role of translational regulation in spatially restricting the production of GRK protein. We then discuss the generality of these mechanisms during oogenesis by focusing on a second transcript, oskar, whose function is also regulated through a combination of transcript localization and translational control.

Merlin, the Drosophila homologue of neurofibromatosis-2, is specifically required in posterior follicle cells for axis formation in the oocyte

In Drosophila, the formation of the embryonic axes is initiated by Gurken, a transforming growth factor alpha signal from the oocyte to the posterior follicle cells, and an unknown polarising signal back to the oocyte. We report that Drosophila Merlin is specifically required only within the posterior follicle cells to initiate axis formation. Merlin mutants show defects in nuclear migration and mRNA localisation in the oocyte. Merlin is not required to specify posterior follicle cell identity in response to the Gurken signal from the oocyte, but is required for the unknown polarising signal back to the oocyte. Merlin is also required non-autonomously, only in follicle cells that have received the Gurken signal, to maintain cell polarity and limit proliferation, but is not required in embryos and larvae. These results are consistent with the fact that human Merlin is encoded by the gene for the tumour suppressor neurofibromatosis-2 and is a member of the Ezrin-Radixin-Moesin family of proteins that link actin to transmembrane proteins. We propose that Merlin acts in response to the Gurken signal by apically targeting the signal that initiates axis specification in the oocyte.

Guidance of cell migration by EGF receptor signaling during Drosophila oogenesis

Directed cell migration is important for many aspects of normal animal development, but little is known about how cell migrations are guided or the mechanisms by which guidance cues are translated into directed cell movement. Here we present evidence that signaling mediated by the epidermal growth factor receptor (EGFR) guides dorsal migration of border cells during Drosophila oogenesis. The transforming growth factor-alpha (TGF-alpha)-like ligand Gurken appears to serve as the guidance cue. To mediate this guidance function, EGFR signals via a pathway that is independent of Raf-MAP kinase and receptor-specific.

Encore is a member of a novel family of proteins and affects multiple processes in Drosophila oogenesis

Mutations in the encore (enc) gene of Drosophila melanogaster cause one extra round of mitosis in the germline, resulting in the formation of egg chambers with extra nurse cells. In addition, enc mutations affect the accumulation of Gurken protein within the oocyte, leading to the production of ventralized eggs. Here we show that enc mutants also exhibit abnormalities in karyosome morphology, similar to other ventralizing mutants such as okra and spindle B. Unlike these mutants, however, the defects in Gurken accumulation and karyosome formation do not result from activation of a meiotic checkpoint. Furthermore, we demonstrate that the requirement for enc in these processes is temporally distinct from its role in germline mitosis. Cloning of the enc locus and generation of anti-Enc antibodies reveal that enc encodes a large novel protein that accumulates within the oocyte cytoplasm and colocalizes with grk mRNA. We argue that the enc mutant phenotypes reflect a role for Enc in the regulation of several RNA targets.

Expression of fringe is down regulated by Gurken/Epidermal Growth Factor Receptor signalling and is required for the morphogenesis of ovarian follicle cells

Signalling by the Gurken/Epidermal Growth Factor Receptor (Grk/EGFR) pathway is involved in epithelial cell fate decision, morphogenesis and axis establishment in Drosophila oogenesis. In the search for genes downstream of the Grk/EGFR signal transduction pathway (STP), we isolated a number of genes that are components of other STPs. One of them is a known gene, called fringe (fng). Drosophila fng encodes a putative secreted protein that is required at other development stages for mediating interactions between dorsal and ventral cells via Notch signalling. Here we show that fng has a dynamic expression pattern in oogenesis and that its expression in specific groups of follicle cells along the anterior-posterior and dorsal-ventral axes is defined by the repression of fng by Grk. Interfering with fng expression using antisense RNA experiments resulted in a typical fng mutant phenotype in the wing, and malformed egg chambers and abnormal organisation of the follicle cells in the ovaries, revealing that fng is essential in oogenesis for the proper formation of the egg chamber and for epithelial morphogenesis. This has been confirmed by re-examination of fng mutants and analysis of fng mutant clones in oogenesis.

brother of rhomboid, a rhomboid-related gene expressed during early Drosophila oogenesis, promotes EGF-R/MAPK signaling

The Drosophila rhomboid (rho) gene participates in localized activation of EGF-receptor signaling in various developmental settings. The Rhomboid protein has been proposed to promote presentation and/or processing of the membrane-bound Spitz (mSpi) EGF-related ligand to generate an active diffusible form of the ligand. Here, we report on a new rhomboid-related gene identified by sequence similarity searching that we have named brother of rhomboid (brho). In contrast to rho, which is expressed in complex patterns during many stages of development, brho appears to be expressed only during oogenesis. brho transcripts are present in early oocytes and abut posterior follicle cells which exhibit high levels of MAPK activation. brho, like rho, collaborates with Star to promote signaling through the EGF-R/MAPK pathway, and genetic evidence indicates that Brho can activate both the mSpi and the Grk precursor EGF ligands in the wing. We propose that endogenous brho may activate the oocyte-specific Gurken ligand and thereby participate in defining posterior cell fates in the early follicular epithelium.

D-cbl, a negative regulator of the Egfr pathway, is required for dorsoventral patterning in Drosophila oogenesis

During Drosophila oogenesis, asymmetrically localized Gurken activates the EGF receptor (Egfr) and determines dorsal follicle cell fates. Using a mosaic follicle cell system we have identified a mutation in the D-cbl gene which causes hyperactivation of the Egfr pathway. Cbl proteins are known to downregulate activated receptors. We find that the abnormal Egfr activation is ligand dependent. Our results show that the precise regulation of Egfr activity necessary to establish different follicle cell fates requires two levels of control. The localized ligand Gurken activates Egfr to different levels in different follicle cells. In addition, Egfr activity has to be repressed through the activity of D-cbl to ensure the absence of signaling in the ventral most follicle cells.

The Mirror transcription factor links signalling pathways in Drosophila oogenesis

Many genetic cascades are conserved in evolution, yet they trigger different responses and hence determine different cell fates at specific times and positions in development. At stage 10 of oogenesis, mirror is expressed in anterior-dorsal follicle cells, and we show that this is dependent upon the Gurken signal from the oocyte. The fringe gene is expressed in a complementary pattern in posterior-ventral follicle cells at the same stage. Ectopic expression of mirror represses fringe expression, thus linking the epidermal growth factor receptor (EGFR) signalling pathway to the Fringe signalling pathway via Mirror. The EGFR pathway also triggers the cascade that leads to dorsal-ventral axis determination in the embryo. We used twist as an embryonic marker for ventral cells. Ectopic expression of mirror in the follicle cells during oogenesis ultimately represses twist expression in the embryo, and leads to similar phenotypes to the ectopic expression of the activated form of EGFR. Thus, mirror also controls the Toll signalling pathway, leading to Dorsal nuclear transport. In summary, we show that the Mirror homeodomain protein provides a link that coordinates the Gurken/EGFR signalling pathway (initiated in the oocyte) with the Fringe/Notch/Delta pathway (in follicle cells). This coordination is required for epithelial morphogenesis, and for producing the signal in ventral follicle cells that determines the dorsal/ventral axis of the embryo.

sog and dpp exert opposing maternal functions to modify toll signaling and pattern the dorsoventral axis of the Drosophila embryo

The short gastrulation (sog) and decapentaplegic (dpp) genes function antagonistically in the early Drosophila zygote to pattern the dorsoventral (DV) axis of the embryo. This interplay between sog and dpp determines the extent of the neuroectoderm and subdivides the dorsal ectoderm into two territories. Here, we present evidence that sog and dpp also play opposing roles during oogenesis in patterning the DV axis of the embryo. We show that maternally produced Dpp increases levels of the I(kappa)B-related protein Cactus and reduces the magnitude of the nuclear concentration gradient of the NF(kappa)B-related Dorsal protein, and that Sog limits this effect. We present evidence suggesting that Dpp signaling increases Cactus levels by reducing a signal-independent component of Cactus degradation. Epistasis experiments reveal that sog and dpp act downstream of, or in parallel to, the Toll receptor to reduce translocation of Dorsal protein into the nucleus. These results broaden the role previously defined for sog and dpp in establishing the embryonic DV axis and reveal a novel form of crossregulation between the NF(kappa)B and TGF(beta) signaling pathways in pattern formation.

A role for the DP subunit of the E2F transcription factor in axis determination during Drosophila oogenesis

The E2F family of transcription factors contributes to cell cycle control by regulating the transcription of DNA replication factors. Functional ‘E2F’ is a DNA-binding heterodimer composed of E2F and DP proteins. Drosophila contains two E2F genes (dE2F, dE2F2) and one DP gene (dDP). Mutation of either dE2F or dDP eliminates G(1)-S transcription of known replication factors during embryogenesis and compromises DNA replication. However, the analysis of these mutant phenotypes is complicated by the perdurance of maternally supplied gene function. To address this and to further analyze the role of E2F transcription factors in development we have phenotypically characterized mitotic clones of dDP mutant cells in the female germline. Our analysis indicates that dDP is required for several essential processes during oogenesis. In a fraction of the mutant egg chambers the germ cells execute one extra round of mitosis, suggesting that in this tissue dDP is uniquely utilized for cell cycle arrest rather than cell cycle progression. Mutation of dDP in the germline also prevents nurse cell cytoplasm transfer to the oocyte, resulting in a ‘dumpless’ phenotype that blocks oocyte development. This phenotype likely results from both disruption of the actin cytoskeleton and a failure of nurse cell apoptosis, each of which are required for normal cytoplasmic transfer. Lastly, we found that dDP is required for the establishment of the dorsal-ventral axis, as loss of dDP function prevents the localized expression of the EGFR ligand Gurken in the oocyte, which initiates dorsal-ventral polarity in the egg chamber. Thus we have uncovered new functions for E2F transcription factors during development, including an unexpected role in pattern formation.

Localization of gurken RNA in Drosophila oogenesis requires elements in the 5' and 3' regions of the transcript

During Drosophila oogenesis, signaling between the germline and the soma leads to the establishment of polarity in the egg and embryo. This process involves the interaction of gurken (grk), a TGFalpha-like protein, with torpedo (top), the Drosophila EGF receptor (Egfr). In early stage egg chambers, grk RNA is present predominantly along the posterior cortex of the oocyte, and in mid stage egg chambers, the grk transcript becomes tightly localized to the future dorsal anterior corner of the oocyte. This localization of grk RNA restricts the distribution of Gurken protein and is critical in defining both the anterior-posterior and dorsal-ventral axes of the egg. We have determined the genomic sequence of the grk gene. By testing the requirement of various fragments of grk RNA in the localization process, we find localization signals present in both the 5' and 3' regions of the gene. Sequences in the 5' noncoding region allow for accumulation of the transcript within the oocyte in early stage egg chambers, while signals in the coding region and the 3'UTR are necessary for localization in mid to late stage egg chambers. Active translation is not required for localization of the grk RNA. The mechanism of gurken RNA localization, therefore, differs from that of other localized RNAs studied to date.

Drosophila bunched integrates opposing DPP and EGF signals to set the operculum boundary

The Drosophila BMP homolog DPP can function as a morphogen, inducing multiple cell fates across a developmental field. However, it is unknown how graded levels of extracellular DPP are interpreted to organize a sharp boundary between different fates. Here we show that opposing DPP and EGF signals set the boundary for an ovarian follicle cell fate. First, DPP regulates gene expression in the follicle cells that will create the operculum of the eggshell. DPP induces expression of the enhancer trap reporter A359 and represses expression of bunched, which encodes a protein similar to the mammalian transcription factor TSC-22. Second, DPP signaling indirectly regulates A359 expression in these cells by downregulating expression of bunched. Reduced bunched function restores A359 expression in cells that lack the Smad protein MAD; ectopic expression of BUNCHED suppresses A359 expression in this region. Importantly, reduction of bunched function leads to an expansion of the operculum and loss of the collar at its boundary. Third, EGF signaling upregulates expression of bunched. We previously demonstrated that the bunched expression pattern requires the EGF receptor ligand GURKEN. Here we show that activated EGF receptor is sufficient to induce ectopic bunched expression. Thus, the balance of DPP and EGF signals sets the boundary of bunched expression. We propose that the juxtaposition of cells with high and low BUNCHED activity organizes a sharp boundary for the operculum fate.

Combined activities of Gurken and decapentaplegic specify dorsal chorion structures of the Drosophila egg

During Drosophila oogenesis Gurken, associated with the oocyte nucleus, activates the Drosophila EGF receptor in the follicular epithelium. Gurken first specifies posterior follicle cells, which in turn signal back to the oocyte to induce the migration of the oocyte nucleus from a posterior to an anterior-dorsal position. Here, Gurken signals again to specify dorsal follicle cells, which give rise to dorsal chorion structures including the dorsal appendages. If Gurken signaling is delayed and starts after stage 6 of oogenesis the nucleus remains at the posterior pole of the oocyte. Eggs develop with a posterior ring of dorsal appendage material that is produced by main-body follicle cells expressing the gene Broad-Complex. They encircle terminal follicle cells expressing variable amounts of the TGFbeta homologue, decapentaplegic. By ectopically expressing decapentaplegic and clonal analysis with Mothers against dpp we show that Decapentaplegic signaling is required for Broad-Complex expression. Thus, the specification and positioning of dorsal appendages along the anterior-posterior axis depends on the intersection of both Gurken and Decapentaplegic signaling. This intersection also induces rhomboid expression and thereby initiates the positive feedback loop of EGF receptor activation, which positions the dorsal appendages along the dorsal-ventral egg axis.

The transmembrane region of Gurken is not required for biological activity, but is necessary for transport to the oocyte membrane in Drosophila

During Drosophila oogenesis, localization of the transforming growth factor alpha (TGFalpha)-like signaling molecule Gurken to the oocyte membrane is required for polarity establishment of the egg and embryo. To test Gurken domain functions, full-length and truncated forms of Gurken were expressed ectopically using the UAS/Gal4 expression system, or in the germline using the endogenous promoter. GrkDeltaC, a deletion of the cytoplasmic domain, localizes to the oocyte membrane and can signal. GrkDeltaTC, which lacks the transmembrane and cytoplasmic domains, retains signaling ability when ectopically expressed in somatic cells. However, in the germline, the GrkDeltaTC protein accumulates throughout the oocyte cytoplasm and cannot signal. In addition, we found that several strong gurken alleles contain point mutations in the transmembrane region. We conclude that secretion of Gurken requires its transmembrane region, and propose a model in which the gene cornichon mediates this process.