A Combined DNA/RNA-based Next-Generation Sequencing Platform to Improve the Classification of Pancreatic Cysts and Early Detection of Pancreatic Cancer Arising From Pancreatic Cysts

OBJECTIVE

We report the development and validation of a combined DNA/RNA next-generation sequencing (NGS) platform to improve the evaluation of pancreatic cysts.

BACKGROUND AND AIMS

Despite a multidisciplinary approach, pancreatic cyst classification, such as a cystic precursor neoplasm, and the detection of high-grade dysplasia and early adenocarcinoma (advanced neoplasia) can be challenging. NGS of preoperative pancreatic cyst fluid improves the clinical evaluation of pancreatic cysts, but the recent identification of novel genomic alterations necessitates the creation of a comprehensive panel and the development of a genomic classifier to integrate the complex molecular results.

METHODS

An updated and unique 74-gene DNA/RNA-targeted NGS panel (PancreaSeq Genomic Classifier) was created to evaluate 5 classes of genomic alterations to include gene mutations (e.g., KRAS, GNAS, etc.), gene fusions and gene expression. Further, CEA mRNA ( CEACAM5 ) was integrated into the assay using RT-qPCR. Separate multi-institutional cohorts for training (n=108) and validation (n=77) were tested, and diagnostic performance was compared to clinical, imaging, cytopathologic, and guideline data.

RESULTS

Upon creation of a genomic classifier system, PancreaSeq GC yielded a 95% sensitivity and 100% specificity for a cystic precursor neoplasm, and the sensitivity and specificity for advanced neoplasia were 82% and 100%, respectively. Associated symptoms, cyst size, duct dilatation, a mural nodule, increasing cyst size, and malignant cytopathology had lower sensitivities (41-59%) and lower specificities (56-96%) for advanced neoplasia. This test also increased the sensitivity of current pancreatic cyst guidelines (IAP/Fukuoka and AGA) by >10% and maintained their inherent specificity.

CONCLUSIONS

PancreaSeq GC was not only accurate in predicting pancreatic cyst type and advanced neoplasia but also improved the sensitivity of current pancreatic cyst guidelines.

Targeted next-generation sequencing panel (GlioSeq) provides comprehensive genetic profiling of central nervous system tumors

BACKGROUND

Identification of genetic changes in CNS tumors is important for the appropriate clinical management of patients. Our objective was to develop a next-generation sequencing (NGS) assay for simultaneously detecting the various types of genetic alterations characteristic for adult and pediatric CNS tumors that can be applied to small brain biopsies.

METHODS

We report an amplification-based targeted NGS assay (GlioSeq) that analyzes 30 genes for single nucleotide variants (SNVs) and indels, 24 genes for copy number variations (CNVs), and 14 types of structural alterations in BRAF, EGFR, and FGFR3 genes in a single workflow. GlioSeq performance was evaluated in 54 adult and pediatric CNS tumors, and the results were compared with fluorescence in-situ hybridization, Sanger sequencing, and reverse transcription PCR.

RESULTS

GlioSeq correctly identified 71/71 (100%) genetic alterations known to be present by conventional techniques, including 56 SNVs/indels, 9 CNVs, 3 EGFRvIII, and 3 KIAA1549-BRAF fusions. Only 20 ng of DNA and 10 ng of RNA were required for successful sequencing of 100% frozen and 96% formalin-fixed, paraffin-embedded tissue specimens. The assay sensitivity was 3%-5% of mutant alleles for SNVs and 1%-5% for gene fusions. The most commonly detected alterations were IDH1, TP53, TERT, ATRX. CDKN2A, and PTEN in high-grade gliomas, followed by BRAF fusions in low-grade gliomas and H3F3A mutations in pediatric gliomas.

CONCLUSIONS

GlioSeq NGS assay offers accurate and sensitive detection of a wide range of genetic alterations in a single workflow. It allows rapid and cost-effective profiling of brain tumor specimens and thus provides valuable information for patient management.

Use of transcriptional profiling to delineate the initial response of mice to intravaginal herpes simplex virus type 2 infection

Intravaginal (ivag) infection of mice with herpes simplex virus type 2 (HSV-2) causes genital tissue damage, quickly followed by development of fatal encephalopathy. To delineate initial host responses generated by HSV-2 infection, here oligonucleotide microarrays compared gene expression in vaginal tissue from uninfected mice and mice 1, 2, 3, 4, 5, 6, or 7 days after ivag infection with 10(4) pfu HSV-2. While comparison of mRNA expression in uninfected and HSV-infected vaginal tissue detected few changes during the first 2 days post infection (dpi), there were 156 genes whose expression was first significantly altered 3 dpi that remained significantly modified at all later time points examined. These 156 genes were significantly enriched in canonical pathways associated with interferon (IFN) signaling, activation of IFN elements by intracellular pattern recognition receptors, and antiviral immunity induced by cytosolic RIG-like receptors. Evaluation of this gene set with the National Center for Biotechnology Information Gene and INTERFEROME databases corroborated pathway analysis, as function of most (53%) were linked to IFN-mediated host immunity. In the final set of experiments, ivag administration of the Toll-like receptor 3 agonist polyinosinic: polycytidylic acid (poly I:C) 24 h before ivag HSV-2 infection reduced the incidence of genital pathology and encephalopathy, while these poly I:C-treated mice were subsequently protected from ocular HSV-2 challenge lethal to uninfected controls. The latter results imply that the exuberant antiviral immunity produced in our experimental model is simply formed too late to prevent viral replication and dissemination, and that poly I:C-induced formation of an antiviral state protecting against primary ivag infection also permits development of HSV-specific protective immunity.

Dendritic cell activation and memory cell development are impaired among mice administered medroxyprogesterone acetate prior to mucosal herpes simplex virus type 1 infection

Epidemiological studies indicate that the exogenous sex steroid medroxyprogesterone acetate (MPA) can impair cell-mediated immunity, but mechanisms responsible for this observation are not well defined. In this study, MPA administered to mice 1 wk prior to HSV type 1 (HSV-1) infection of their corneal mucosa impaired initial expansion of viral-specific effector and memory precursor T cells and reduced the number of viral-specific memory T cells found in latently infected mice. MPA treatment also dampened expression of the costimulatory molecules CD40, CD70, and CD80 by dendritic cells (DC) in lymph nodes draining acute infection, whereas coculture of such DC with T cells from uninfected mice dramatically impaired ex vivo T cell proliferation compared with the use of DC from mice that did not receive MPA prior to HSV-1 infection. In addition, T cell expansion was comparable to that seen in untreated controls if MPA-treated mice were administered recombinant soluble CD154 (CD40L) concomitant with their mucosal infection. In contrast, the immunomodulatory effects of MPA were infection site dependent, because MPA-treated mice exhibited normal expansion of virus-specific T cells when infection was systemic rather than mucosal. Taken together, our results reveal that the administration of MPA prior to viral infection of mucosal tissue impairs DC activation, virus-specific T cell expansion, and development of virus-specific immunological memory.

Microtubules modulate melatonin receptors involved in phase-shifting circadian activity rhythms: in vitro and in vivo evidence

MT1 melatonin receptors expressed in Chinese hamster ovary (CHO) cells remain sensitive to a melatonin re-challenge even following chronic melatonin exposure when microtubules are depolymerized in the cell, an exposure that normally results in MT1 receptor desensitization. We extended our findings to MT2 melatonin receptors using both in vitro and in vivo approaches. Using CHO cells expressing human MT2 melatonin receptors, microtubule depolymerization prevents the loss in the number of high potency states of the receptor when compared to melatonin-treated cells. In addition, microtubule depolymerization increases melatonin-induced PKC activity but not PI hydrolysis via Gi proteins similar to that shown for MT1Rs. Furthermore, microtubule depolymerization in MT2-CHO cells enhances the exchange of GTP on Gi-proteins using a photoaffinity analog of GTP. To test whether microtubules are capable of modulating melatonin-induced phase-shifts, microtubules are depolymerized specifically within the suprachiasmatic nucleus of the hypothalamus (SCN) of the Long Evans rat and the efficacy of melatonin to phase shift their circadian activity rhythms was assessed and compared to animals with intact SCN microtubules. We find that microtubule depolymerization in the SCN using either Colcemid or nocodazole enhances the efficacy of 10 pm melatonin to phase-shift the activity rhythms of the Long Evans rat. No enhancement occurs in the presence of beta-lumicolchicine, the inactive analog of Colcemid. Taken together, these data suggest that microtubule dynamics can modulate melatonin-induced phase shifts of circadian activity rhythms which may explain, in part, why circadian disturbances occur in individuals afflicted with diseases associated with microtubule disturbances.

MT1 melatonin receptor internalization underlies melatonin-induced morphologic changes in Chinese hamster ovary cells and these processes are dependent on Gi proteins, MEK 1/2 and microtubule modulation

Melatonin induces cellular differentiation in numerous cell types. Data show that multiple mechanisms are involved in these processes that are cell-type specific and may be receptor dependent or independent. The focus of this study was to specifically assess the role of human MT1 melatonin receptors in cellular differentiation using an MT1-Chinese hamster ovary (CHO) model; one that reproducibly produces measurable morphologic changes in response to melatonin. Using multiple approaches, we show that melatonin induces MT1-CHO cells to hyperelongate through a MEK 1/2, and ERK 1/2-dependent mechanism that is dependent upon MT1 receptor internalization, Gi protein activation, and clathrin-mediated endocytosis. Using immunoprecipitation analysis, we show that MT1 receptors form complexes with Gi(alpha) 2,3, Gq(alpha), beta-arrestin-2, MEK 1/2, and ERK 1/2 in the presence of melatonin. We also show that MEK and ERK activity that is induced by melatonin is dependent on Gi protein activation, clathrin-mediated endocytosis and is modulated by microtubules. We conclude from these studies that melatonin-induced internalization of human MT1 melatonin receptors in CHO cells is responsible for activating both MEK 1/2 and ERK 1/2 to drive these morphologic changes. These events, as mediated by melatonin, require Gi protein activation and endocytosis mediated through clathrin, to form MT1 receptor complexes with beta-arrestin-2/MEK 1/2 and ERK 1/2. The MT1-CHO model is invaluable to mapping out signaling cascades as mediated through MT1 receptors especially because it separates out MEK/ERK 1/2 activation by MT1 receptors from that of receptor tyrosine kinases.

The Associations Between Pelvic Inflammatory Disease, Trichomonas vaginalis Infection, and Positive Herpes Simplex Virus Type 2 Serology

OBJECTIVE

Roles for Chlamydia trachomatis and Neisseria gonorrhoeae infections in pelvic inflammatory disease pathogenesis are well delineated; however, the etiologic contributions of herpes simplex virus type 2 (HSV-2) and Trichomonas vaginalis have been underexplored.

GOAL

The goal of this study was to investigate the association between acute and plasma cell endometritis, fallopian tube obstruction, HSV-2 serology, and T. vaginalis infection.

STUDY DESIGN

The authors conducted a cross-sectional secondary analysis of 736 women at risk for bacterial sexually transmitted diseases that used endometrial biopsy data obtained at enrollment as well as hysterosalpingography results obtained 12 weeks after enrollment.

RESULTS

Women diagnosed with T. vaginalis at enrollment were more likely to have histologic evidence of acute endometritis. Both plasma cell and acute endometritis were significantly more common among women with positive serology HSV-2; furthermore, women coinfected with HSV-2 and C. trachomatis, N. gonorrhoeae, T. vaginalis, or bacterial vaginosis were much more likely to be diagnosed with acute endometritis than were women infected with HSV-2 or one of these pathogens alone. Among women with available HSV-2 serology and hysterosalpingogram results, HSV-2 was the only genital tract pathogen infection associated with fallopian tube obstruction.

CONCLUSIONS

Our analyses demonstrate that T. vaginalis infection and positive HSV-2 serology are associated with endometritis. Further work will be needed to determine the specific roles these pathogens may play in pelvic inflammatory disease pathogenesis.

Differential effects of endoplasmic reticulum stress-induced autophagy on cell survival

Autophagy is a cellular response to adverse environment and stress, but its significance in cell survival is not always clear. Here we show that autophagy could be induced in the mammalian cells by chemicals, such as A23187, tunicamycin, thapsigargin, and brefeldin A, that cause endoplasmic reticulum stress. Endoplasmic reticulum stress-induced autophagy is important for clearing polyubiquitinated protein aggregates and for reducing cellular vacuolization in HCT116 colon cancer cells and DU145 prostate cancer cells, thus mitigating endoplasmic reticulum stress and protecting against cell death. In contrast, autophagy induced by the same chemicals does not confer protection in a normal human colon cell line and in the non-transformed murine embryonic fibroblasts but rather contributes to cell death. Thus the impact of autophagy on cell survival during endoplasmic reticulum stress is likely contingent on the status of cells, which could be explored for tumor-specific therapy.

Modulation of melatonin receptors and G-protein function by microtubules

Chronic melatonin exposure produces microtubule rearrangements in Chinese hamster ovary (CHO) cells expressing the human MT1 melatonin receptor while at the same time desensitizing MT1 receptors. Because microtubule rearrangements parallel MT1 receptor desensitization, we tested whether microtubules modulate receptor responsiveness. We determined whether depolymerization of microtubules by Colcemid, which prevents melatonin-induced outgrowths in MT1-expressing CHO cells, also prevents MT1 receptor desensitization by affecting G(alpha)-GTP exchange on G-proteins. In this study, we found that depolymerization of microtubules in MT1 receptor expressing cells, prevented melatonin-induced receptor desensitization reflected by an increase in the number of high potency sites when compared with melatonin-treated cells. Further examination of the mechanism(s) underlying this desensitization suggested that these effects occurred at the level of G-proteins. Depolymerization of microtubules during melatonin-induced desensitization, attenuated forskolin-induced cAMP accumulation, the opposite of which usually occurs following melatonin exposure alone. Concomitant to this attenuation in the forskolin response was a reduction in the amount of G(i alpha) protein coupled to MT1 receptors and an increase in [32P] azidoanilido GTP incorporation into G(i) proteins. These data are consistent with the findings that microtubule depolymerization did not affect MT1/G(q) coupling nor did it affect melatonin-induced phosphoinositide hydrolysis following melatonin exposure. However, interestingly, microtubule depolymerization enhanced melatonin-induced protein kinase C activation that was blocked in the presence of pertussis toxin. These data demonstrate that microtubule dynamics can modulate melatonin receptor function through their actions on G(i) proteins and impact on downstream signaling cascades.

Molecular analysis of the simultaneous production of two SHV-type extended-spectrum beta-lactamases in a clinical isolate of Enterobacter cloacae by using single-nucleotide polymorphism genotyping

Bacteria that simultaneously produce multiple extended-spectrum beta-lactamases are frequently isolated. We report an Enterobacter cloacae isolate, ES24, producing four different beta-lactamases (AmpC type beta-lactamase, TEM-1, SHV-7, and a novel extended-spectrum beta-lactamase, SHV-30). Direct sequencing of bla(SHV) gene products gave a "double peak" at position 703, suggesting the presence of more than one allele. Using fluorescence resonance energy transfer real-time PCR to detect single-nucleotide polymorphisms, we were able to distinguish two different bla(SHV) genes in a single isolate. This may prove to be a useful technique in surveys of beta-lactamase production in contemporary clinical isolates.

Genital tract shedding of herpes simplex virus type 2 in women: effects of hormonal contraception, bacterial vaginosis, and vaginal group B Streptococcus colonization

BACKGROUND

Genital infections due to herpes simplex virus type 2 (HSV-2) are characterized by frequent reactivation and shedding of the virus and by the attendant risk of transmission to sexual partners. We investigated the effects of vaginal coinfections and hormonal contraceptive use on genital tract shedding of HSV-2 in women.

METHODS

A total of 330 HSV-2-seropositive women were followed every 4 months for a year. At each visit, one vaginal swab specimen was obtained for detection of HSV-2 by polymerase chain reaction, a second vaginal swab specimen was obtained for detection of group B Streptococcus (GBS) organisms and yeast by culture, and a vaginal smear was obtained for the diagnosis of bacterial vaginosis by Gram staining.

RESULTS

HSV-2 DNA was detected in 88 (9%) of 956 vaginal swab specimens. Independent predictors of genital tract shedding of HSV-2 were HSV-2 seroconversion during the previous 4 months (adjusted odds ratio [aOR], 3.0; 95% confidence interval [CI], 1.3-6.8), bacterial vaginosis (aOR, 2.3; 95% CI, 1.3-4.0), high-density vaginal GBS colonization (aOR, 2.2; 95% CI, 1.3-3.8), and use of hormonal contraceptives (aOR, 1.8; 95% CI, 1.1-2.8).

CONCLUSIONS

The present study identifies hormonal contraceptive use, bacterial vaginosis, and high-density vaginal GBS colonization as risk factors for genital tract shedding of HSV-2 in women. Because hormonal contraceptives are used by millions of women worldwide and because bacterial vaginosis and vaginal GBS colonization are common vaginal conditions, even modest associations with HSV-2 shedding would result in substantial attributable risks for transmission of the virus.

Knock-down of RGS4 and beta tubulin in CHO cells expressing the human MT1 melatonin receptor prevents melatonin-induced receptor desensitization

Previously, it has been shown that chronic melatonin exposure in MT1-CHO cells results in receptor desensitization while at the same time producing drastic morphological changes. The addition of a depolymerizing agent during the melatonin pretreatment period prevents MT1 receptor desensitization and the changes in cellular morphology. The lack of morphological change in the presence of a depolymerizing agent is easily explained by the inability of the microtubules to polymerize, however, the prevention of receptor desensitization is a little more complex and may involve G-protein activation. The goal of this study was to determine whether melatonin-induced MT1 receptor desensitization is regulated by proteins known to regulate G-protein activation states, beta-tubulin and RGS4,using anti sense knockdown approaches. The expression of RGS4 mRNA in CHO cells was confirmed using RT PCR and successful knockdown of each was confirmed by western blot analysis or quantitative PCR. Pretreatment of MT1-CHO cells, transfected with the nonsense probes and exposed to melatonin, resulted in a desensitization of the receptor, an increase in forskolin-induced cAMP accumulation, an increase in 2-[125I]-iodomelatonin binding and no change in the affinity of melatonin for the MT1 receptor. However, knockdown of either beta-tubulin or RGS4 in MT1-CHO cells followed by pretreatment with melatonin attenuated the desensitization of melatonin receptors, decreased total 2-[125I]-iodomelatonin binding, and did not affect neither the forskolin response nor the affinity of melatonin for the MT1 receptor. Perhaps RGS4 and beta-tubulin modulate Galpha-GDP and Galpha-GTP states thus modulating MT1 melatonin receptor function.

Melatonin receptors and their regulation: biochemical and structural mechanisms

There is growing evidence demonstrating the complexity of melatonin's role in modulating a diverse number of physiological processes. This complexity could be attributed to the fact that melatonin receptors belong to two distinct classes of proteins, that is, the G-protein coupled receptor superfamily (MT(1), MT(2)) and the quinone reductase enzyme family (MT(3)) which makes them unique at the molecular level. Also, within the G-protein coupled receptor family of proteins, the MT(1) and MT(2) receptors can couple to multiple and distinct signal transduction cascades whose activation can lead to unique cellular responses. Also, throughout the 24-hour cycle, the receptors' sensitivity to specific cues fluctuates and this sensitivity can be modulated in a homologous fashion, that is, by melatonin itself, and in a heterologous manner, that is, by other cues including the photoperiod or estrogen. This sensitivity of response may reflect changes in melatonin receptor density that also occurs throughout the 24-hour light/dark cycle but out of phase with circulating melatonin levels. The mechanisms that underlie the changes in melatonin receptor density and function are still not well-understood, but data is beginning to show that transcriptional events and G-protein uncoupling may be involved. Even though this area of research is still in its infancy, great strides are being made everyday in elucidating the mechanisms that underlie melatonin receptor function and regulation. The focus of this review is to highlight some of these discoveries in an attempt to reveal the uniqueness of the melatonin receptor family while at the same time provide thought-provoking ideas to further advance this area of research. Thus, a brief overview of each of the mammalian melatonin receptor subtypes and the signal transduction cascades to which they couple will be discussed with a greater emphasis placed on the mechanisms underlying their regulation and the domains within the receptors essential for proper signaling.

Dual coupling of MT(1) and MT(2) melatonin receptors to cyclic AMP and phosphoinositide signal transduction cascades and their regulation following melatonin exposure

In this investigation, we wanted to determine whether MT(1) or MT(2) melatonin receptors are capable of coupling to the phosphoinositide (PI) signal transduction cascade. In addition, we wanted to assess the effects of chronic melatonin exposure on MT(1) and MT(2) melatonin receptor-mediated stimulation of PI hydrolysis. We also assessed the effects of chronic melatonin exposure on other parameters of the MT(2) melatonin receptor function including total specific 2-[125I]-iodomelatonin binding, the affinity of melatonin for the receptor, and melatonin (1nM)-mediated inhibition of cyclic 3',5'-adenosine monophosphate (cAMP) accumulation. Investigation of the PI signal transduction cascade activated by either the MT(1) or MT(2) melatonin receptor expressed in Chinese hamster ovary (CHO) cells showed that melatonin (1pM to 1mM) was able to stimulate the formation of PIs to approximately 40-60% over basal [EC(50): MT(1)=29nM (2-300nM) and MT(2)=1.1nM (0.32-3.5nM), N=5]. This response was mediated via receptors based upon the findings that melatonin did not stimulate the formation of PIs in CHO cells devoid of receptor and that antagonism of MT(2) melatonin receptors by 4P-PDOT (AH 024; 4-phenyl-2-propionamidotetralin) attenuated melatonin-mediated stimulation of PI hydrolysis in CHO cells expressing the MT(2) melatonin receptor. The consequence of chronic melatonin exposure on MT(1) and MT(2) receptor function was also examined. Pretreatment of either MT(1)- or MT(2)-CHO cells with melatonin (1 microM for 5hr) resulted in: (a) a complete loss of melatonin-mediated stimulation of PI hydrolysis, and (b) an attenuation of melatonin (1nM)-mediated inhibition of forskolin-induced cAMP accumulation by approximately 20-40%. The desensitization of the PI hydrolysis signal transduction cascades coupled to either MT(1) or MT(2) melatonin receptors following chronic melatonin exposure was not due to depleted phospholipid pools, to elevated basal levels, or to decreases in receptor affinity and density. This dual coupling of melatonin receptors to different signal transduction cascades may contribute to the diversity of melatonin receptor function in vivo.

N1E-115 mouse neuroblastoma cells express MT1 melatonin receptors and produce neurites in response to melatonin

Melatonin, a pineal hormone that induces sleep, has become a popular over-the-counter drug. The cellular effects of melatonin, however, are only beginning to be studied. We have recently shown that stimulation of the MT1 melatonin receptor induces rapid and dramatic cytoskeletal rearrangements in transformed non-neuronal cells (Witt-Enderby et al., Cell. Motil. Cytoskel. 46 (2000) 28). These cytoskeletal changes result in the formation of structures that closely resemble neurites. In this work, we show that the N1E-115 mouse neuroblastoma cell line rapidly responds to melatonin stimulation and forms neurites within 24 h. We also demonstrate that these cells readily bind 2-[125I]iodomelatonin at levels consistent with what is noted for native tissues (B(max)=3.43+/-1.56 fmol/mg protein; K(d)=240 pM). Western analysis shows that these cells possess and express melatonin receptors of the MT1 subtype. Treatment with pertussis toxin eliminates neurite formation whereas treatment with the MT2 subtype-specific activator, BMNEP, does not induce neurite formation. We have previously shown that increases in MEK 1/2 and ERK 1/2 phosphorylation are correlated with the shape changes in transformed CHO cells. Western analysis of the MEK/ERK signaling pathway in N1E-115 cells shows that this pathway is most likely maximally and constitutively stimulated. This may account for the spontaneous production of neurites noted for this cell line after long culture periods. The results of this work show that melatonin receptor stimulation in a neuronal cell type results in the formation of neurites and that the receptors responsible for melatonin-induced neurite formation in N1E-115 cells are most likely of the MT1 subtype.

Melatonin induction of filamentous structures in non-neuronal cells that is dependent on expression of the human mt1 melatonin receptor

Melatonin has gained recent popularity as a treatment for insomnia and other sleep disorders; however, its cellular effects are unknown. We report the effects of melatonin on the cellular morphology of Chinese hamster ovary (CHO) cells transformed to express the human melatonin receptors, mt1 and MT2. Our results show that melatonin exerts a strong influence on cellular shape and cytoskeletal organization in a receptor-dependent and possibly subtype-selective manner. The cell shape change that we see after a 5-h treatment of these non-neuronal cells with a pharmacological concentration of melatonin consists of the formation of long filamentous outgrowths that are reminiscent of the neurite processes produced by differentiating nerve cells. This morphological change occurs exclusively in cells expressing the mt1 receptor. We find that the microtubule and microfilament organization within these outgrowths is similar to that of neurites. Microtubules are required for the shape change to occur as Colcemid added in combination with melatonin completely blocks outgrowth formation. We demonstrate that the number of cells showing the altered cell shape is dependent on melatonin concentration, constant exposure to melatonin and that outgrowth frequencies increase when protein kinase A (PKA) is inhibited. Concomitant melatonin-dependent increases in MEK 1/2 and ERK 1/2 phosphorylation are noted in mt1-CHO cells only. The production of filamentous outgrowths is dependent on the translation of new protein but not the transcription of new mRNA. Outgrowth number is not controlled by centrosomes but is instead controlled by the polymerization state of the actin cytoskeleton. The results of this work show that the organization of the cytoskeleton is affected by processes specifically mediated or regulated by the mt1 receptor and may represent a novel alternative mechanism for the stimulation of process formation.

Melatonin decreases cell proliferation and transformation in a melatonin receptor-dependent manner

There are conflicting claims for the role of melatonin in oncogenesis. In addition, the mechanism(s) underlying melatonin's effects in oncogenic processes is (are) unknown. In this study, the effects of melatonin exposure on cell proliferation and transformation were assessed in NIH3T3 cells transfected with either the human mt(1) (NIH-mt1) or MT(2) (NIH-MT2) melatonin receptors. The effects of melatonin exposure on proliferation was assessed by direct cell counts and [(3)H]thymidine uptake assays. The effect of chronic melatonin pretreatment on transformation was assessed by focus assays. In both NIH-mt1 and NIH-MT2 cells, melatonin pretreatment decreased cell proliferation and transformation. Control (NIH-neo) cells did not show this effect. However, as revealed by the [(3)H]thymidine uptake assays, an increase in DNA synthesis occurred in NIH-mt1 cells, whereas no increase occurred in the NIH-MT2 or NIH-neo cells. Upon examination of melatonin receptors, a decrease in the function of both mt(1) and MT(2) receptors occurred. These data suggest that perhaps an attenuation of receptor-mediated processes are involved in the anti-proliferative and anti-transformation capabilities of melatonin in NIH3T3 cells. In addition, based on the [(3)H]thymidine assays, receptor mediated signal transduction mechanisms may slow the growth of cells via actions on the cell cycle. The results from this study shed new insight on the putative mechanisms underlying melatonin's effects on cell proliferation and transformation and lends support for a protective role of melatonin in oncogenesis.

Structure and sequence of the Arabidopsis thaliana lipoxygenase 1 gene

We have isolated and sequenced the Arabidopsis thaliana LOX1 gene which encodes a lipoxygenase. The 5255 bp sequence includes 763 bp upstream from the start codon, 4345 bp spanning the coding region and 147 bp downstream from the stop codon. The coding region of the LOX1 gene consists of 8 exons separated by 7 introns. The introns in the LOX1 gene are located in sites predicted by the closely related soybean seed LOX3 gene sequence. With the exception of intron 1, the LOX1 introns are smaller in size than the LOX3 introns. Furthermore the Arabidopsis gene contains 7 introns, while the soybean gene contains 8. Four putative TATA box elements were identified in the 763 bp sequence upstream from the coding region, however only one is followed by a cap site which is located in a position appropriate for it to act as the initiation site for transcription.

An Arabidopsis thaliana lipoxygenase gene can be induced by pathogens, abscisic acid, and methyl jasmonate

We isolated and characterized a 2.8-kb, full-length, Arabidopsis thaliana cDNA clone encoding a lipoxygenase. DNA sequence analysis showed that the deduced amino acid sequence of the Arabidopsis protein is 72 to 78% similar to that of legume seed lipoxygenases. DNA blot analysis indicated that Arabidopsis contains a single gene, LOX1, with appreciable homology to the cDNA clone. RNA blot analysis showed that the LOX1 gene is expressed in Arabidopsis leaves, roots, inflorescences, and young seedlings. LOX1 expression levels were highest in roots and young seedlings. In mature plants, LOX1 mRNA levels increased upon treatment with the stress-related hormones abscisic acid and methyl jasmonate and remained high for at least 96 h. Expression of the LOX1 gene was examined following infiltration of leaves with virulent (Psm ES4326) and avirulent (Pst MM1065) strains of Pseudomonas syringae. LOX1 mRNA levels were induced approximately 6-fold by both virulent and avirulent strains; however, the response to avirulent strains was much more rapid. Infiltration of leaves with Pst MM1065 resulted in maximal induction within 12 h, whereas maximal induction by Psm ES4326 did not occur until 48 h. When a cloned avr gene, avrRpt2, was transferred to Psm ES4326, LOX1 mRNA accumulated in a pattern similar to that observed for the avirulent strain Pst MM1065.

Redistribution and differential extraction of soluble proteins in permeabilized cultured cells. Implications for immunofluorescence microscopy

Immunofluorescence microscopy is widely used to characterize the cellular distribution of both soluble and structural proteins. Control experiments generally address only the specificity of the antibodies used. The permeabilization/fixation conditions used to prepare cells for antibody application are assumed to preserve faithfully the in vivo distributions of the protein(s) being examined. We systematically tested the extent to which soluble proteins are redistributed into inappropriate locations and are differentially extracted from native locations during the permeabilization and fixation of the cells before antibody application. We separately introduce six soluble FITC-conjugated proteins of different net charges and sizes into living cultured cells. The labeled proteins do not adhere to the external surfaces of living cells and are evenly distributed throughout the cytoplasm with the larger proteins being excluded from the nucleus. The cells are then prepared as if for immunofluorescence using several conditions that encompass many of the methods commonly used for this purpose. Cells permeabilized with 0.1-0.2% Triton X-100 before fixation with 3.7% paraformaldehyde show a striking localization of all but one of the test proteins to the nucleus and/or nucleoli of 60–80% of labeled cells. Punctate cytoplasmic labeling and cytoskeletal-like arrays of labeled protein are also observed. Extraction with 1% detergent prior to fixation removes most but not always all of the exogenous proteins from the cell remnants. Permeabilization of cells with 0.1% detergent after paraformaldehyde fixation leaves a reticular, uneven cytoplasmic distribution of the labeled proteins, and some of the larger proteins are redistributed to the nuclei. Direct fixation/permeabilization with -20 degrees C methanol largely preserves the in vivo distributions of fluorescent proteins with some preferential localization of these proteins to nuclei, nucleoli and the perinuclear region. These results show that misleading apparent localizations of soluble proteins can result from their redistribution and/or differential extraction during the preparation of cells for primary antibody application.

Evidence against the involvement of ionically bound cell wall proteins in pea epicotyl growth

Ionically bound cell wall proteins were extracted from 7 day old etiolated pea (Pisum sativum L. cv Alaska) epicotyls with 3 molar LiCl. Polyclonal antiserum was raised in rabbits against the cell wall proteins. Growth assays showed that treatment of growing region segments (5-7 millimeters) of peas with either dialyzed serum, serum globulin fraction, affinity purified immunoglobulin, or papain-cleaved antibody fragments had no effect on growth. Immunofluorescence microscopy confirmed antibody binding to cell walls and penetration of the antibodies into the tissues. Western blot analysis, immunoassay results, and affinity chromatography utilizing Sepharose-bound antibodies confirmed recognition of the protein preparation by the antibodies. Experiments employing in vitro extension as a screening measure indicated no effect upon extension by antibodies, by 50 millimolar LiCl perfusion of the apoplast or by 3 molar LiCl extraction. Addition of cell wall protein to protease pretreated segments did not restore extension nor did addition of cell wall protein to untreated segments increase extension. It is concluded that, although evidence suggests that protein is responsible for the process of extension, the class(es) of proteins which are extracted from pea cell walls with 3 molar LiCl are probably not involved in this process.