Position statement on the diagnosis and management of congenital pituitary deficiency in adults: the French National Diagnosis and Treatment Protocol (NDTP)

Pituitary deficiency, or hypopituitarism, is a rare chronic disease. It is defined by insufficient synthesis of one or more pituitary hormones (growth hormone, TSH, ACTH, LH-FSH, prolactin), whether or not associated with arginine vasopressin deficiency (formerly known as diabetes insipidus). In adult patients, it is usually acquired (notably during childhood), but can also be congenital, due to abnormal pituitary development. The present study focuses on congenital pituitary deficiency in adults, from diagnosis to follow-up, including special situations such as pregnancy or the elderly. The clinical presentation is highly variable, ranging from isolated deficit to multiple deficits, which may be part of a syndromic form or not. Diagnosis is based on a combination of clinical, biological (assessment of all hormonal axes), radiological (brain and hypothalamic-pituitary MRI) and genetic factors. Treatment consists in hormonal replacement therapy, adapted according to the period of life and the deficits, which may be progressive. Comorbidities, risk of complications and acute decompensation, and the impact on fertility and quality of life all require adaptative multidisciplinary care and long-term monitoring.

Acute Bulbar Palsy and Ophtalmoplegia Associated With Anti-GT1a IgG Antibodies

INTRODUCTION

Although several variants of Guillain-Barré syndrome (GBS) have been described, they are uncommon, and the atypical clinical presentation of patients makes the diagnosis challenging. This article reports a case of acute bulbar palsy plus (ABPp) syndrome.

CASE REPORT

A 18-year-old patient was admitted to our hospital because of difficulty swallowing, slurred speech, tingling of the extremities of the 4 limbs, and diplopia. He reported abdominal pain and diarrhea 2 weeks earlier. Physical examination showed a low-pitched voice, palsy elevation of the soft palate and complete palsy of the abduction of the left eye. Electromyography and cerebrospinal fluid examination were unremarkable, but Campylobacter jejuni serology was positive, and we found an isolated immunoglobulin G (IgG) anti-GT1a antibodies positivity. A diagnosis of ABPp was finally made, and the patient fully recovered early after receiving polyvalent immunoglobulins infusion.

CONCLUSIONS

ABPp is classified as subtype of GBS. The most frequent clinical signs of ABPp are ophthalmoplegia, facial palsy, and ataxia. IgG anti-GT1a and/or anti-GQ1b are positive in a majority of patients with ABPp; however, these antibodies are not specific and can found in other subtypes of GBS.

Transition kinetics of mixed lipid:photosurfactant assemblies studied by time-resolved small angle X-ray scattering

HYPOTHESIS

Photoswitchable surfactants are used in the design of many light-responsive colloids and/or self-assemblies. Photo-isomerization enables to control molecular equilibrium, and triggers transient reorganizations with possibly out-of-equilibrium intermediate states that have been overlooked. Here, we address this question by an in depth structural investigation of intermediate lipid-surfactant assemblies that occur during fast isothermal photo-triggered transition in lipid:surfactant mixtures.

EXPERIMENTS

The structural parameters of mixed assemblies of azobenzene-containing cationic surfactant (AzoTMA) and dioleoylphosphatidylcholine (DOPC) lipids were studied by light scattering and time-resolved small angle X-ray scattering. Structural and compositional information about the assemblies and unimers in bulk were determined at the photostationary states, as well as at intermediate kinetic states formed during UV or blue light illumination.

FINDINGS

DOPC:AzoTMA systems form mixed assemblies representative of phospholipid:cationic surfactant mixtures, that evolve from spheroid, to rod-like micelles, and vesicles with increasing DOPC fraction. Transient assemblies detected during the photo-triggered kinetics are similar to the ones found in stationary states. But changes of AzoTMA unimers in bulk can be considerably faster than mass reorganizations of the mixed assemblies, suggesting that out-of-equilibrium conditions are transiently reached. Mass reorganization of the surfactant-enriched assemblies is much faster than in the lipid enriched ones, providing insight into the role of lipids in a slow reorganization of the assemblies.

Perfusion-weighted techniques in MRI grading of pediatric cerebral tumors: efficiency of dynamic susceptibility contrast and arterial spin labeling

PURPOSE

Dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) perfusion MRI are applied in pediatric brain tumor grading, but their value for clinical daily practice remains unclear. We explored the ability of ASL and DSC to distinguish low- and high-grade lesions, in an unselected cohort of pediatric cerebral tumors.

METHODS

We retrospectively compared standard perfusion outcomes including blood volume, blood flow, and time parameters from DSC and ASL at 1.5T or 3T MRI scanners of 46 treatment-naive patients by drawing ROI via consensus by two neuroradiologists on the solid portions of every tumor. The discriminant abilities of perfusion parameters were evaluated by receiver operating characteristic (ROC) over the entire cohort and depending on the tumor location and the magnetic field.

RESULTS

ASL and DSC parameters showed overall low to moderate performances to distinguish low- and high-grade tumors (area under the curve: between 0.548 and 0.697). Discriminant abilities were better for tumors located supratentorially (AUC between 0.777 and 0.810) than infratentorially, where none of the metrics reached significance. We observed a better differentiation between low- and high-grade cancers at 3T than at 1.5-T. For infratentorial tumors, time parameters from DSC performed better than the commonly used metrics (AUC ≥ 0.8).

CONCLUSION

DSC and ASL show moderate abilities to distinguish low- and high-grade brain tumors in an unselected cohort. Absolute value of K2, TMAX, tMIP, and normalized value of TMAX of the DSC appear as an alternative to conventional parameters for infratentorial tumors. Three Tesla evaluation should be favored over 1.5-Tesla.

Molecular cloning and expression pattern of the DP members of the chicken E2F transcription factor

The DP proteins are components of the E2F transcription factor. They form heterodimers with the E2F proteins and these complexes bind efficiently to E2F response elements in promoters of genes that are involved in cell cycle regulation. The properties of the DP proteins are less documented than those of their E2F counterpart and the present work was aimed at characterizing avian DP genes (named chDP) and their products. Here we describe the cloning of the chicken homologues of the mammalian DP-1 and DP-2 proteins. This work also suggests that DP-2 isoforms have an additional 60 amino acid extension at the N-terminus compared to its human counterpart. Gel-shift assays and coimmunoprecipitation show that both DP-1 and DP-2 dimerize to chE2F-1 and activate transcription efficiently, as demonstrated by transient expression assays. However, contrary to the expression patterns exhibited by E2F-1 during the cell cycle or during neuroretina development, DP member's expression appears more invariant, suggesting that E2F activity is limited by the availability of the E2F proteins.

[Computer-assisted therapy and video games in psychosocial rehabilitation for schizophrenia patients]

OBJECTIVES

Video games and virtual reality have recently become used by clinicians for training or information media or as therapeutic tools. The purpose is to review the use of these technologies for therapy destined for schizophrenia patients.

METHODS

We conducted a review in October 2016 using Pubmed, Scopus and PsychInfo using the following Medical Subject Headings (MESH): "video games", "virtual reality" and "therapy, computer-assisted/methods", each associated with "schizophrenia". Papers were included in the review if: (a) they were published in an English, Spanish or French-language peer-reviewed journal, (b) the study enrolled patients with schizophrenia or schizo-affective disorder, (c) the patients used a therapeutic video game or therapeutic virtual reality device.

RESULTS

Eighteen publications were included. The devices studied are mainly therapeutic software developed specifically for therapeutic care. They can be classified according to their therapeutic objectives. These targets corresponded to objectives of psychosocial rehabilitation: improvement of residual symptomatology, cognitive remediation, remediation of cognition and social skills, improvement of everyday life activities, support for occupational integration. Very different devices were proposed. Some researchers analysed programs developed specifically for patients with schizophrenia, while others were interested in the impact of commercial games. Most of the studies were recent, preliminary and European. The impact of these devices was globally positive, particularly concerning cognitive functions.

CONCLUSIONS

Computer-assisted therapy, video games and virtual reality cannot replace usual care but could be used as adjunctive therapy. However, recommending their use seems premature because of the recent and preliminary character of most studies. Moreover, a link is still lacking between this field of research in psychiatry and other fields of research, particularly game studies. Finally, it might be interesting to analyse more precisely the neuropsychological impact of existing commercial games which could potentially be useful for psychosocial rehabilitation.

Prise en charge de personnes âgées dans les services d’urgences psychiatriques, critères d’hospitalisation et motifs de consultation : état des lieux au SAAU de Pau

Le nombre de personnes âgées (PA) est en constante augmentation en France comme dans les pays développés. Les PA de plus de 75 ans représentaient 8 % de la population métropolitaine en 2002. Elles seront selon l’INSEE 9,6 % en 2020 et 16,1 % en 2040. Parallèlement de plus en plus de patients relevant de prise en charge gérontopsychiatrique se présentent dans les services d’urgences notamment psychiatriques.

Au CHS de Pau il existe un service d’urgence psychiatrique (SAAU) pour les admissions et un service de 20 lits d’hospitalisation de gérontopsychiatrie pour les patients de plus de 75 ans souffrant de pathologie psychiatrique.

La décision d’hospitalisation en psychiatrie est une décision médicale. Elle ne se conçoit que pour les personnes âgées dont le pronostic vital n’est pas engagé et présentant de troubles psychiatriques aiguës ou chroniques avec signes de décompensation aiguë sans comorbidités neurologiques ou démentielles décompensées. Toute situation ne nécessitant pas d’hospitalisation en psychiatrie ferait objet d’un suivi par l’équipe mobile de gérontopsychiatrie et permettrait de garantir un retour à la structure d’origine (domicile ou autre) avec l’assurance d’un suivi et d’une continuité des soins. Cependant, il apparaît que les décisions de prise en charge ne sont pas en adéquation avec ses principes en particulier en ce qui concerne les motifs principaux d’hospitalisation.

Afin de faire le point sur les indications d’hospitalisation en gérontopsychiatrie nous avons réalisé une étude rétrospective concernant les patients de plus de 75 ans s’étant présenté au SAAU de Pau au cours du 1er trimestre 2014.

Nous nous sommes intéressés à recueillir via les dossiers informatisés des patients les motifs de consultations, les antécédents ainsi que le devenir de ceux-ci.

Broadband supercontinuum interferometer for high-resolution profilometry

In this paper, it is shown that a white light supercontinuum source generated in an air-silica microstructured optical fiber pumped with picosecond pulses offers the possibility to improve fringes visibility in interferometric acquisitions. Consequently, this source combined with a spectral interferometer, reaches high-resolution profilometric measurements. Phase calculation based on seven point algorithm can perform theoretically a subnanometer resolution. This method provides a one line profile of large surfaces from the analysis of a single shot image, without any mechanical scanning.

Imaging through a scattering medium with an interferential spectrometer by selection of an amplitude modulation correlator

Low-coherence interferometric systems provide three-dimensional imaging through scattering media by measurement of the object's temporal response. An optical correlator is presented that allows direct recording of the signal issued from the object under reflection. The filtering technique enhances the image visibility and allows one to obtain an image with a good signal-to-noise ratio. The performance of two particular imaging systems, point-to-point and vertical-slice imaging, is discussed with an object comprising two cover plates that are attached.

High-resolution optical correlation imaging in a scattering medium

An optical correlation setup is used to image transparent objects through scattering media, and 10-mum longitudinal and 2.5-mum transverse resolution are achieved. Spectral-bandwidth sampling of the light source is made possible by a tunable dye laser and leads to signal enhancement as a result of sampling interferogram filtering. An optical system allows observation of sample slices without the need for a translation stage.

Partial combination applied to phylogeny of European cyprinids using the mitochondrial control region

Previous molecular phylogenies of European cyprinids led to some solid facts and some uncertainties. This study is based on a stretch of more than 1 kb in the mitochondrial control region newly sequenced for 35 European cyprinids and on previous cytochrome b and 16S rDNA data. The trees based on the control region are more accurate and robust than those obtained from the two other genes. Character incongruence among the three genes was tested using the incongruence length difference (ILD) test. Iterative removals of individual sequences followed by new ILD tests identified two sequences responsible for statistically significant incongruence. A partial combination was conducted, that is, a combination of the three data sets, removing the two sequences previously identified. The phylogenetic analysis of this partial combination gives a more robust and resolved picture of subfamilial interrelationships. The Rasborinae are the sister group of all other cyprinids. The monophyletic Cyprininae emerges next. Tinca tinca first and then Rhodeus are the sister groups of all the remaining nonrasborine and noncyprinine species. Gobio is the sister group of the Leuciscinae, in which the Phoxinini are the sister group of the Leuciscini. Within the Leuciscini, the genus Leuciscus and the subfamily Alburninae are both paraphyletic. The Rasborinae are the most basal cyprinid subfamily and the Tincinae are not the sister group of the Cyprininae. These two results challenge only two anatomical characters, which need to be reinterpreted or considered as homoplastic in cyprinid evolution: the modification of the first pleural rib and its parapophysis and the bony composition of the interorbital septum.

Performance of 18S rDNA helix E23 for phylogenetic relationships within and between the Rotifera-Acanthocephala clades

The species diversity of the phylum Rotifera has been largely studied on the basis of morphological characters. However, cladistic relationships within this group are poorly resolved due to extensive homoplasy in morphological traits, substantial phenotypic plasticity and a poor fossil record. We undertook this study to determine if a phylogeny based on partial 18S rDNA, which included the helix E23 of 18S rDNA sequence, was concordant with established taxonomic relationships within the order Ploimida (class: Monogononta). We also estimated the level of polymorphism within clones and populations of Ploimida 'species'. Finally, we included the Cycliophora Symbion pandora as outgroup and the variable helix E23 region to examine the influence of their signal on the evolutionary relationships among Acanthocephala, Bdelloidea and Ploimida. Phylogenetic reconstruction was performed using maximum parsimony, neighbour joining and maximum likelihood methods. We found 1) that morphologically similar Ploimida 'species' show vastly different 18S E23 rDNA sequences; 2) inclusion of the helix E23 of 18S rDNA and its secondary structure analysis results in better resolution of family level relationships within the Ploimida; 3) an impact of Symbion pandora as an outgroup with inclusion of the helix E23 on the relationships between the Rotifera and the Acanthocephala; and 4) partial incongruence and differential substitution rate between conserved region and helix E23 region of the 18S rDNA gene depending on the taxomic group studied.

Long-term results and prognostic factors in patients with epithelial ovarian cancer

OBJECTIVES

The aim of this study was to evaluate long-term results and to assess prognostic factors which have an impact on overall survival in patients with epithelial ovarian cancer.

METHODS

A retrospective analysis of 287 patients treated between 1975 and 1995 was performed. All operations were performed by senior surgeons. Histologic sections were reviewed by the same pathologist. Successive adjuvant chemotherapy regimens are described. Survival was evaluated in 1997. Follow-up lasted 25-260 months (median 90). Statistical methods included Kaplan-Meier survival curves, log-rank test, and multivariate analysis.

RESULTS

The 5-year survival rates were 76, 42, 21, and 6% for patients with stage I, II, III, and IV disease, respectively. Age, FIGO stage, cytology of ascites, histologic type and grade, extent of surgery, and number of residual tumors were significant prognostic indicators in univariate analysis. Multivariate analysis showed that the risk of mortality according to FIGO stage was 2.8, 95% CI [1.2-6.3], P = 0.01 for FIGO II, 5.6, 95% CI [2.9-10.8], P < 0.001 for FIGO III, and 10.5, 95% CI [4.9-22. 1], P < 0.001 for FIGO IV in comparison with FIGO I. Patients with a serous epithelial carcinoma had a 1.7-fold higher risk of mortality than patients with other histologic types: RR = 1.7, 95% CI [1.1-2. 8], P < 0.001. Patients whose tumors distribution permitted optimal surgery had a 2.3-fold lower risk of mortality than patients treated with sub- or nonoptimal surgery: RR = 0.43, 95% CI [0.29-0.64], P < 0.001. The risk of mortality for patients treated with alkylating agents, platinum-based combination chemotherapy without taxanes, or carboplatin plus paclitaxel regimens compared with patients who did not receive treatment was reduced by 47%, 95% CI [8-69%], P = 0.025, 55%, 95% CI [22-74%], P = 0.005, and 70%, 95% CI [35-86%], P = 0.002, respectively.

CONCLUSION

Our study confirms the benefit of cytoreductive surgery and the efficacy of platinum plus paclitaxel first-line chemotherapy which has recently been recognized as the standard treatment for advanced epithelial ovarian cancer.

Unusual regulation of cyclin D1 and cyclin-dependent kinases cdk2 and cdk4 during in vivo mitotic stimulation of olfactory neuron progenitors in adult mouse

The molecular mechanisms underlying cell cycle control in neuronal progenitors have been investigated with adult mouse olfactory epithelium as a model system. Odor receptive neurons of mammalian olfactory epithelium are short-lived and renewed in the adult by mitotic division of intrinsic neuronal progenitors. Ablation of the synaptic target, olfactory bulb, induces sequentially extensive apoptosis of sensory neurons and then stimulation of progenitor proliferation, peaking at 36 h and 4 days, respectively, postlesion. Known molecular effectors of G1 phase entry have been assessed on protein extracts of olfactory organs sampled at various postbulbectomy times in adult mice. The decay of betaIII-tubulin and olfactory marker protein levels and the rise of proliferating cell nuclear antigen (PCNA) levels, starting 1 and 3 days, respectively, postlesion, provided the kinetic frame of neuronal dynamics. Cyclin D1, cyclin E, and cyclin-dependent kinase cdk2 levels, low in olfactory organ of intact mice, increased 3 days after bulbectomy in parallel with PCNA levels; cdk4 content was initially high and unaffected by lesioning. Western blots of the known cdk inhibitors revealed proliferation-related decreases of p18, p21, and p27 from high expression in intact organs. Immunoprecipitation of cdk2 and cdk4 fractions of protein extracts at 4 days postlesion (mitotic reaction peak) versus control, followed by cyclin D1 immunoblotting, and vice versa, revealed that levels of both cyclin D1/cdk2 and cyclin D1/cdk4 complexes, as well as their kinase activities, were dramatically increased after lesion. In vivo proliferation of olfactory neuronal lineage cells thus involves functional binding of cyclin D1 with cdk2 and cdk4, with differential activation mechanisms for cdk2 and cdk4. In addition, the RT-PCR-detected cyclin D1 mRNA level remained unaffected after bulbectomy, which indicated that the cyclin D1 rise should involve posttranscriptional mechanisms in this in vivo neuronal system. These observations are discussed, along with their relevance to cell cycle control and to olfactory neuron dynamics.

[Prognostic factors for survival of ovarian epithelial cancers: apropos of 287 cases]

OBJECTIVES

To evaluate survival and assess prognostic factors in patients with epithelial ovarian cancer.

METHODS

Retrospective analysis of 287 patients treated between 1975 and 1995. All operations were performed by senior surgeons. Histologic sections were reviewed by the same pathologist. Successive adjuvant chemotherapy regimens are described. Survival was evaluated in 1997. Follow-up lasted 25-260 months (median 90). Statistical methods included Kaplan-Meier survival curves, logrank test and multivariate analysis.

RESULTS

The five-year survival rates 76%, 42%, 21% and 6% for patients with stage I, II, III and IV disease, respectively. Age, FIGO stage, cytology of ascites, histologic type and grade, extent of surgery and number of residual tumors were significant prognostic indicators in univariate analysis. Multivariate analysis showed that the risk of mortality was reduced by 57% for patients whose tumor distribution permitted optimal surgery (RR = 0.43, 95% CI [0.29-0.64]; P < 0.001). The risk of mortality according to FIGO stage was 2.8 (95% CI [1.2-6.3]; P = 0.01) for FIGO II, 5.6 (95% CI [2.9-10.8]; P < 0.001) for FIGO III and 10.5 (95% CI [4.9-22.1]; P < 0.001) for FIGO IV in comparison with FIGO I. The risk of mortality for patients treated with alkylating agents, platinum-based combination chemotherapy taxanes or carboplatin plus paclitaxel regimen compared with patients who did not receive treatment was reduced by 47% (95% CI [8%-69%]; P = 0.025), 55% (95% CI [22%-74%]; P = 0.005) and 70% (95% CI [35%-86%]; P = 0.002), respectively. Patients with a serous epithelial carcinoma had a 1.7-fold higher risk of mortality than patients with other histologic types (RR = 1.7, 95% CI [1.1-2.8]; P = 0.02).

CONCLUSION

Our study confirms the benefit of cytoreductive surgery and the efficacy of platinum plus paclitaxel first-line chemotherapy, which has recently been recognized as the standard treatment for advanced epithelial ovarian cancer.

Regulation of cdc2 gene expression by the upstream stimulatory factors (USFs)

cdc2 gene expression is under the control of multiple factors. Although E2F/DP proteins have been reported to play a central role, they cannot account for all aspects of the fine modulation of cdc2 gene expression during cell cycle and embryonic development. To characterize the transcription factors that control cdc2 gene expression during nerve cell differentiation in avians, we have previously cloned the quail cdc2 gene promoter region. We had identified an octamer (CAGGTGGC) containing an E-box, which has important activity in regulating cdc2 transcription. Using in vivo genomic footprinting experiments, we show here that this motif, currently named IG, is the target of binding proteins at different stages of neuroretina development, confirming its importance as a regulatory response element for cdc2 gene expression. A subset of Helix-Loop-Helix family of transcription factors, known as Upstream Stimulatory Factors (USFs) specifically bind to this sequence as dimers. Moreover, our results indicate that USFs transactivate the promoter of cdc2 via the IG motif. These data may help to better understand the mechanisms that control cell division in differentiating nerve cells.

Regulation by pH of the alternative splicing of the stem cell factor pre-mRNA in the testis

Proliferation and differentiation of progenitor stem cells are mainly controlled by diffusible and adhesion molecules. Stem cell factor (SCF), an essential regulator of spermatogenesis produced by Sertoli cells, utilize both modes of cell to cell communication. Indeed, SCF exists in soluble (SCFs) and membrane-bound (SCFm) forms, which are required for a complete spermatogenesis, and are generated by alternative splicing of optional exon 6, encoding sites of proteolysis. We show that in the mouse testis, the alternative splicing of SCF is developmentally regulated. SCFs predominates in fetal and neonatal gonads and is then replaced by SCFm in the prepubertal and adult gonads. By sequencing SCF exon 6, we show that the flanking intronic sequences perfectly follow the gt-at rule, suggesting that the basal splicing machinery might not be responsible by itself for exon 6 skipping. Moreover, freshly isolated Sertoli cells mainly express SCFm, but a switch to SCFs occurs after 48 h of culture. We found that this change can be prevented by acidification of the culture medium at pH 6.3 or by addition of lactate. The sustained synthesis of SCFm at low pH was no longer observed in the presence of cycloheximide, suggesting that SCF exon 6 skipping requires de novo protein synthesis. Accordingly, UV cross-linking experiments show that nuclear Sertoli cell protein(s) bind in a sequence-specific manner to exon 6. Together, our data allow the proposal of an integrated mechanism in which the synthesis of lactate by Sertoli cells is used in the same time as an energetic substrate for germ cells and as a promoter of their survival/proliferation through the production of SCFm.

Transient accumulation of retinoblastoma/E2F-1 protein complexes correlates with the onset of neuronal differentiation in the developing quail neural retina

Retinoblastoma (Rb) protein has been implicated in the control of cell proliferation and malignant transformation in different cell types. To analyze its role as a promoter of cell growth arrest during development, we have studied the temporal pattern of Rb expression and its association with E2F-1 during embryogenesis of the quail neuroretina. During development of this neural organ, most cells stop dividing and begin to differentiate at embryonic days E6 and E7, as indicated by the decline of cyclin-dependent kinase cdk2 and by an increased level of cdk5. At this stage, we observed a shift of hyperphosphorylated Rb protein to its hypophosphorylated form as well as a decrease of the total level of Rb. The Rb-related protein, p107, is also progressively down-regulated from the E7 stage onwards. P130 levels, on the other hand, actually increase. Moreover, cell cycle exit at E6-E7 is characterized by a sudden and transient rise of the E2F-1/RB complex followed by the appearance of the E2F-4/p130 complex starting at E8. Conversely, expression of adenovirus E1A protein in E6 neuroretina cells leads to a dissociation of E2F-1/Rb complex and suppression of cell growth arrest and differentiation. This suggests that cell cycle exit and re-entry may depend on Rb/E2F-1 interaction. Although the rate of Rb synthesis declines in postmitotic cells, as suggested by in vivo metabolic labeling of the Rb protein, the level of the Rb transcript remains

Regulation of E2F-1 gene expression in avian cells

E2F-1 is the prototype of a family of transcription factors playing a central role in the control of cell proliferation and apoptosis. E2F DNA binding activity is down-regulated during cellular differentiation, which is correlated with cell division arrest. We report here that the expression of E2F-1 itself is down-regulated in the developing quail neural retina between embryonic days E8-E10. This event occurs just after the massive arrest of the quail neuroretina cell division (E7-E8). To gain further insight into the regulatory mechanisms monitoring E2F-1 expression in differentiating neurons, we have cloned the quail E2F-1 promoter. In vivo DNA footprintings of this promoter have shown that a number of potential SP-1 and C/EBP response elements are constitutively occupied in the entire quail neuroretina of E5 and E14, whereas the two consensus palindromic E2F binding sites are only protected at E5. This suggests that these E2F elements participate in down-regulation of E2F-1 gene expression during avian neuroretina development. CAT reporter assays have shown that E2F-1 in association with its partner DP-1 transactivates its own promoter, whereas p105Rb inhibits the E2F-1 promoter. Both E2F-1/DP-1 and p105Rh require the presence of the E2F binding sites to mediate their effects. However, experiments performed with deletion mutants of the promoter strongly suggest that other regions located upstream of the E2F binding sites also mediate part of the E2F-1 transactivating effect on its own promoter. Altogether, these results suggest that the down-regulation of E2F-1 gene expression in differentiating neurons could be due, in part, to the E2F/Rb complexes binding to the E2F-1 promoter.

Mitochondrial phylogeny of the European cyprinids: implications for their systematics, reticulate evolution, and colonization time

Two different mitochondrial genes, the cytochrome b and the 16S rDNA, support the same European cyprinid molecular phylogeny: the most basal subfamily is the paraphyletic Rasborinae, the Cyprininae are monophyletic, the Tincinae and Gobioninae are close to the Cyprininae or more basal lineages but not close to Leuciscinae or Alburninae, and the Leuciscinae are paraphyletic but can become monophyletic if we include the biphyletic alburninae and exclude the Phoxinini. The relationship of the Acheilognathinae remains obscure. Natural intergeneric and interspecific hybridizations are clearly demonstrated within the Leuciscinae, both from high bootstrap proportions and intermediate morphological features: Chondrostoma toxostoma and Rutilus rutilus, Scardinius erythrophthalmus and R. rutilus, and Leuciscus multicellus and Leuciscus soufia. Finally, the use of the nonsaturated and clockwise 16S mtDNA sequences have been used to infer from nonintrogressive taxa the time of the first European cyprinid cladogeneses. The estimation confirms the hypothesis of Almaça and Banarescu that European cyprinid subfamilies started to diversify 35 mya and confirms the hypothesis of Bianco on the diversification of European leuciscines in the Mediterranean area during the late Messinian (6.5 to 5.3 mya).

Cytologic findings in a neovagina created with Vecchietti's technique for treating vaginal aplasia

OBJECTIVE

To report long-term cytologic findings after treatment of congenital vaginal aplasia or Mayer-Rokitansky-Küster-Hauser syndrome (MRKH) using progressive traction of the vulvar tissues, or Vecchietti's technique (VT).

STUDY DESIGN

In eight women with MRKH, neovaginal smears stained by the Harris-Schorr technique were collected 2-12 years after VT.

RESULTS

Eosinophilic superficial cells observed in all cases indicate that the neovaginal epithelium responds to hormonal variations. The presence of Döderlein bacilli (seven cases) suggests that the regional environment of the neovagina is almost the same as that of the normal vagina. Gardnerella vaginalis (one case) and human papilloma virus infection (low grade squamous intraepithelial lesions) (one case) were also observed.

CONCLUSION

Neovaginal smears taken after the cicatrization period following construction of a neovagina by VT show a remarkable resemblance to those from normal vaginal mucosa and suggest that these neovaginas are almost the same as normal vaginas.

Axillary lymphadenectomy prepared by fat and lymph node suction in breast cancer

AIMS

To describe a new technique of axillary dissection and evaluate the results.

METHODS

Axillary lymphadenectomy prepared by fat and lymph node suction was performed on 43 patients with breast cancer and uninvolved axilla on physical examination. The mean follow-up was 18 months (range 12-27). After lipolysis and liposuction of the axilla, lymph node dissection was performed by axilloscopy in patients treated with conservative surgery. For patients undergoing modified radical mastectomy, a mastectomy with open axillary dissection was carried out. The axillary space was drained until less than 20 ml of lymphorrhea was being produced per day. Seventeen modified radical mastectomies (group M) and 26 lumpectomies (group L) were performed.

RESULTS

No injury of muscles, vessels or nerves was observed. An average of 13.6 lymph nodes (8-31) were removed. In group L, the mean number of lymph nodes removed by liposuction, axilloscopy and control incision was 2.5, 5.4 and 4.2, respectively. In group M, the mean number of lymph nodes removed was 14. None of the 589 lymph nodes examined showed any pathological trauma. Fourteen patients (32%) had more than one histologically positive node. The mean quantity of lymphorrhea was 390 ml in group M and 275 ml in group L. The mean duration of drainage was 6 days in group M and 5 days in group L. Four patients had seromas which required punctures. Two patients had shoulder restriction (movements < 90 degrees) at 12 months. No arm oedema was seen.

CONCLUSIONS

Axillary lymphadenectomy prepared by fat and lymph node suction is a reliable and effective procedure. However, it does not appear to be better than standard dissection as regards post-operative complications, except for arm oedema, but this must be confirmed by further studies.

[Does axillary liposuction modify histologic study of excised lymph nodes?]

OBJECTIVE

To determine the pathological features of lymph nodes removed by axillary liposuction.

METHODS

A prospective study of 34 axillary dissections performed from July 1995 to September 1996 in patients with breast cancer N0. After lipolysis, the fat was drained from the axillary cavity by means of liposuction (Karman nozzle ch.8; suction pressure of 1 Bar). The remaining nodes were removed by an endoscopic dissection in conservative treatments. The remaining nodes were removed during modified radical mastectomy in non-conservative treatments. Lymph nodes were fixed in formol and examined by the pathologist.

RESULTS

An average of 15 lymph nodes (8-35) were removed. 502 lymph nodes were examined: 458 (91%) were not involved and 44 (9%) were involved, including 21 (4%) with rupture of the capsule. No pathological traumatism was seen.

CONCLUSION

Axillary liposuction did not alter the pathological features of lymph nodes in our study.

Stress-induced transcription of the clusterin/apoJ gene

Clusterin/apoJ is an intriguing gene frequently isolated by differential screening in laboratories from different areas of molecular biology, since it is overexpressed in numerous cases of degenerative diseases such as Alzheimer's disease and scrapie. While the dramatic increase of clusterin expression in injured tissues is well established, the molecular basis of the gene induction remains unclear. In this study, we have focused our attention on the only DNA region strictly conserved between clusterin gene proximal promoters from different vertebrate classes. We show that this 14-bp DNA element is specifically recognized by the HSF1 transcription factor and can mediate heat-shock-induced transcription in transient expression assays. Conversely, the avian clusterin proximal promoter, point-mutated at the level of this element, no longer transmits heat-shock activation. These findings provide a possible explanation for the high sensitivity of clusterin expression to environmental changes and allow the classification of clusterin as an extracellular version of heat-shock protein.

[Vulvar tumefactions]

Two types of tumefactions can be distinguished: diffuse, without an actually measurable tumour, and circumscribed, most often corresponding to benign tumours. Among diffuse tumefactions, the author diseases prolapse, inguinal hernias, hematomas, oedemas, vulvar varices, abcesses of the vulva and rare cases of elephantiasis. Each case is described and management is discussed. In a second section, where only large tumours can be termed tumescent, the author discusses cystic formations (serous, mucous and epidermal) and solid formations (fibromas, lipomas, acrochordons, neurofibromas, giant condylomas, voluminous endometriomas, and budding neoplastic mass). Excision of these tumours is always recommended as is pathologic surveillance.

SISAM interferometer for distance measurements

We measure short distances with a spectromètre interférentiel à sélection par l'amplitude de la modulation (SISAM) (interferential spectrometer by selection of amplitude modulation) interferometer that correlates optical fields. We present the method and the resolution of the system. A test with a Michelson interferometer shows SISAM's ability to detect phase change in one arm of the Michelson interferometer.

Optimization of PCR/lambda exonuclease-mediated synthesis of sense and antisense DNA probes for in situ hybridization

In situ hybridization experiments are stringently dependent on the quality of the probes, which should be single-stranded when efficient comparison of signals obtained with antisense and control sense probes are needed. In this report, we describe an optimized synthesis of radioactive single-stranded DNA probes, without vector cloning and requiring a unique polymerization step. The sequence region selected as probe is amplified by polymerase chain reaction in the presence of radiolabelled nucleotides. The sense and antisense probes are then yielded by the action of the lambda bacteriophage exonuclease, which can specifically eliminate one out of the two strands of the amplified fragments. In this way, sense and antisense probes with identical length and specific activity can be generated by selecting the primer to be phosphorylated. We have verified the efficiency of our probes for in situ hybridization of the clusterin transcripts within the peripheral olfactory system, after surgical lesion of its synaptic target.

Recent evolutionary acquisition of alternative pre-mRNA splicing and 3' processing regulations induced by intronic B2 SINE insertion

Contrary to the membrane-anchored leukemia inhibitory factor receptor (LIFR), the mouse soluble LIFR is an inhibitor of LIF action, possibly through a ligand titration effect. Two mRNA species encoding the soluble LIFR have been identified. Since the 3'-untranslated end of the shorter form was shown to contain a B2 element, we have examined the possibility that this SINE may be responsible for LIFR mRNA truncation. Transient expression assays, using B2-derived or intron-derived sequences independently or in conjunction, show that the B2 element has fortuitously unmasked a cryptic pre-mRNA 3'processing activity of silent intron sequences. The corresponding locus of the rat genome has been isolated and was shown to be devoid of any retroposon, which may explain why no soluble LIFR has yet been identified in any other species and further indicates that the B2 insertion event in the mouse LIFR gene has occurred recently during evolution. And yet, a tight tissue-specific regulation of alternative synthesis of soluble and membrane-bound LIFR mRNA has already emerged in mice. These results provide striking evidence for the rapid influence of retroposition on genome expression.

Clusterin/ApoJ expression is associated with neuronal apoptosis in the olfactory mucosa of the adult mouse

The molecular events orchestrating neuronal degeneration and regeneration remain poorly understood. Attempts at identifying genes specifically expressed during these processes, have constantly led to the (re)isolation of the clusterin/ApoJ gene, whose expression is highly reactive to injury in a wide variety of tissues. To get insight into the function of clusterin in neuron loss, we have assessed in detail the clusterin gene expression in an experimental model of neurodegeneration, using the peripheral olfactory system of adult mouse. The sensory neurons of olfactory nasal mucosa can be massively induced to degenerate in vivo, by surgical removal of their only synaptic target: the olfactory bulb. We have previously shown that this neuron loss results from a near-synchronized induction of apoptosis genetic programs. We present here evidence that clusterin gene expression is tightly correlated to the onset of neuronal apoptoses in lesioned olfactory mucosae. The simultaneous preparation of DNA and RNA from the same tissue samples reveals that a strong clusterin mRNA accumulation coincides with the wave of nucleosome-sized DNA fragmentation. However, double detection of apoptotic nuclei by the TUNEL method and of clusterin messengers by in situ hybridization revealed that the clusterin gene expression is not induced in dying neurons, but in the glial sheath surrounding the axon bundles of degenerating olfactory neurons. Clusterin immunocytochemistry reveals that the clusterin protein accumulates not only in these producing cells, but also in the olfactory epithelium, suggesting the possibility of clusterin internalization by cells located at a distance from the synthesis loci. In view of this localization and of the activities of the clusterin protein reported so far, possible functions of clusterin in nervous plasticity are discussed.

Proliferation of chicken neuroretina cells induced by v-src, in vitro, depends on activation of the E2F transcription factor

Quiescent chicken or quail retina neuroblasts (NR) can be induced to proliferate actively, in culture, by the v-src oncoprotein. The chE2F-1 transcription factor, a physiological partner of the retinoblastoma gene product, is highly expressed in vivo, in dividing chicken neuroretina cells (CNR). It is sharply down-regulated as cells enter the post-mitotic differentiation stage, thus suggesting that E2F activity is a prerequisite for NR cell proliferation. In the present paper, transient expression assays of different forms of chE2F-1 were used to investigate the function of E2F for switching CNR cells from a quiescent to a proliferative state in vitro. Attempts to substitute the effects of v-src by an ectopic expression of E2F-1 were unsuccessful. However, in the same conditions, E2F-1 supports full growth of CEF in serum-depleted medium. Deletion mutants of E2F-1, with potential dominant-negative properties, were transfected in RSV infected CNR cells. One of these truncated mutants induces a G1 phase block in RSV-transformed CNR cells indicating that, although E2F-1 overexpression cannot overcome the cell proliferation block of post-mitotic CNR cells E2F-1, activity is an important component of the growth signal pathway delivered by v-src in these nervous cells.

p34(cdc2) and mitotic cyclin expression in the developing quail neuroretina

After an initial proliferation phase, neurons of the central nervous system (CNS) of higher eukaryotes remain postmitotic during their entire lifespan. This requires that a very stringent control be exerted on the cell division apparatus, whose molecular mechanisms remain quite elusive. Here we have used quail neuroretina as a model to study the control of cell division in the developing CNS. In vertebrates, embryonic neuroretinal cells (NR cells) stop their proliferation at different times depending on the cell type. Most NR cells in the quail embryo become postmitotic between E7 and E8. To acquire a better understanding of the molecular events leading to quiescence in NR cells, we have analyzed the expression of cdc2 and of two activators of p34(cdc2): cyclin A and cyclin B2 in the developing neuroretina. We report that these three proteins are downregulated between E7 and E9, suggesting that a common mechanism could block their transcription in differentiating neurons. We also report, using an immunohistochemical approach, that p34(cdc2) downregulation is correlated with the appearance of the microtubule-associated protein tau. These results strongly suggest that inhibition of cdc2 gene expression is closely linked to the achievement of terminal differentiation in neurons. However, we also show that postmitotic ganglion cells precursors begin to synthesize the early neuronal differentiation marker beta3-tubulin while p34(cdc2) is still detectable in these cells, suggesting that p34(cdc2) or a closely related kinase could play a role in some "young" postmitotic neurons.

The product of the v-src-inducible gene nr-13 is a potent anti-apoptotic factor

Tumorigenesis can be induced either by activating cell proliferation or by inhibiting metabolic pathways regulating programmed cell death (apoptosis). There is evidence suggesting that p60(v-src) and other tyrosine kinases protect cells against apoptosis. This effect could contribute to cell transformation by the Rous sarcoma virus. Mechanism of cell death inhibition by p60(v-src) remains largely unknown. We have recently reported that in avian cells p60(v-src) activates the expression of nr-13, a bcl-2-related gene. In this paper, we demonstrate, using the bone marrow derived cell line Baf-3 as an experimental model, that the product of this avian gene (nr-13) is a potent anti-apoptotic factor. In addition, we report that, in quail neuroretinal cells, nr-13 expression is activated upon infection by the Rous sarcoma virus (RSV) but not by other oncogenic retroviruses like FSV or MH2, suggesting that nr-13 is a specific target of v-src. Activation of nr-13 expression may be a key step in cellular transformation by v-src.

Viral inhibition of apoptosis

Viral propagation is limited both by the host immune response and by apoptosis of infected cells. Viruses circumvent apoptosis by different mechanisms: direct inhibition of particular proteases involved in cell death, stimulation of anti-death pathways or regulation of the activity of transcription factors monitoring cell survival.

Two distinct regulatory elements control quail cdc2 transcription: possible involvement in the control of retinoblast differentiation

It is a characteristic of the central nervous system of higher eukaryotes that neurons, after an initial proliferation phase, remain postmitotic for their whole life span. In the developing quail neuroretina, most retinoblasts become postmitotic after 7-8 days of incubation. They also cease to express cdc2, which is presumably necessary to allow retinoblasts to definitively leave the cell cycle. The molecular mechanisms monitoring cdc2 expression during differentiation remain partly understood. To further study the control of cdc2 transcription in avian cells, we have cloned the quail cdc2 promoter. Two functional regulatory elements have been characterized. One of them contains an E2F-binding site. Human E2F-1 was found to transactivate the quail cdc2 promoter very efficiently in avian and human cells. Gel retardation experiments are presented, suggesting that E2F, in association with different partners, is a major regulatory of cdc2 transcription during the development of the neuroretina. Our data also indicate that another transcription factor binds to the octamer CAGGTGGC located 115 nucleotides above the main transcription start site. This motif is thus another important regulatory element participating in the control of cdc2 expression.

Measurement of mode times of flight in multimode fibers by an interferometric method using polychromatic light: theoretical approach and experimental results

The propagation of several modes in an optical fiber is not easy to study. The experiment that we propose permits us to measure the difference in time propagation between two successive modes of a multimode fiber. The same laser beam is coupled into the fiber to be tested and into the reference single-mode fiber. The correlation of output electric fields of the modes propagated by each fiber is realized by an interferometric system.

Isolation and characterization of a chicken homolog of the E2F-1 transcription factor

In higher eukaryotes, the E2F-1 transcription factor is an essential and limiting component of cell cycle progression in late G1. E2F-1 heterodimerizes with members of the DP gene family and the resulting heterodimer regulates the expression of several proto-oncogenes and the genetic machinery of DNA replication. Cell cycle regulation of E2F activity is mediated through its association with the tumor suppressor Rb gene product. To examine the evolutionary conservation of the E2F-1 protein sequence and its developmental expression pattern we have isolated and sequenced the chick E2F-1 gene (chE2F-1) cDNA. The chicken protein is 34 amino acids (a.a) shorter than its human counterpart (403/437 a.a.) but has extremely well conserved bHLH and pRb binding domains, with respectively 94% and 83% identity. The position of the leucine zipper is also strictly conserved thereby accounting for ability of E2F-1 to form heterodimers with human and chicken DP-1. E2F-1 expression was analysed in synchronized cells as well as in embryonic or newborn chick tissues and appears to be closely correlated to the cell proliferation rate. In situ hybridization studies have shown very high expression levels in the neuroretina during the early stages of embryonic development when active neuroblast division occurs. In contrast, a sharp down-regulation is observed when cells become postmitotic. Overexpression of the chE2F-1 protein leads to oncogenic transformation only when a truncated version of the transgene lacking the pRb binding domain is used; the full length protein either has no effect or may be deleterious for cell survival.

A Bcl-2-related gene is activated in avian cells transformed by the Rous sarcoma virus

The oncoprotein p60v-src encoded by the Rous sarcoma virus (RSV) genome is the prototype of non-receptor tyrosine kinases. More than 50 targets of p60v-src have been described to date. However, the precise mechanisms of RSV transformation remain to be elucidated. Here, we present the study of a new v-src-activated gene, NR-13, which encodes a protein identified as a new member of the Bcl-2 family. This protein is localized in the membrane with a pattern already observed with Bcl-2. In quail embryos, this gene is mainly expressed in neural and muscular tissues. Its expression is dramatically down-regulated after embryonic day 7 (E7) in the optic tectum. To evaluate a possible role for NR-13 in the control of apoptotic processes in this particular brain area, in situ hybridization and DNA ladder fractionation studies were performed to correlate NR-13 expression with typical situations of apoptosis during brain development. Our results support the idea that RSV could activate anti-apoptotic functions of the host cell resulting in an increase of their lifespan, which could be particularly relevant to tumour formation.

The expression of the avian clusterin gene can be driven by two alternative promoters with distinct regulatory elements

Clusterin cDNA has been isolated as a copy of a mRNA overexpressed in a wide variety of biological disorders, including tissue regression, brain injuries and oncogenic cell transformation. While the molecular cloning of the rat and the human clusterin genes has revealed a high degree of conservation of the genomic organization between mammals, the avian locus described here illustrates several divergent features. The avian gene has the particularity to be transcribed from at least two different promoters, both of which are active in transient expression assays using the quail QT6 transformed cell line. The detection of the two clusterin mRNA species by reverse-transcription-mediated PCR reveals a coordinated initiation of transcription from both promoters in all organs tested. In possible relation to the bipartite organization of the avian regulatory region, the putative cis-elements described in the unique mammalian promoters appear divided among the two avian promoters. In addition, the sequence comparison of avian and mammalian regulatory sequences has allowed the identification of a conserved putative cis-element which appears to be the target for specific DNA-binding factors.

RNA-dependent DNA binding activity of the Pur factor, potentially involved in DNA replication and gene transcription

The PUR element is a polypurine polypyrimidine motif that can stimulate transcription, encountered in the 5' regions of various genes and in the vicinity of several DNA replication initiation zones. We demonstrate that the PUR complex formation between the purine-rich strand of PUR and nuclear extracts can be prevented by pretreatment of nuclear extracts with RNA-damaging agents such as UV light or RNase A. A biochemical affinity method reveals that small RNA molecules copurify with the Pur factor. Moreover, the PUR binding activity of RNA-depleted nuclear extracts can be restored by addition of phenol-extracted RNAs. This work adds a new member in the emerging class of ribonucleoprotein particles as regulatory factors of the genetic expression.

The relationship of Piry virus to other vesiculoviruses: a re-evaluation based on the glycoprotein gene sequence

By sequencing the 3 half of the Piry virus genome, we show that Piry virus, like the other vesiculoviruses, contains the genes for nucleoprotein N, phosphoprotein P, matrix protein M, glycoprotein G and polymerase protein L, in that order. Our analysis of the Piry G protein sequence suggests that Piry and Chandipura are related to each other as closely as the Indiana and New Jersey vesicular stomatitis virus serotypes are to each other. A re-examination of amino acid sequences in the nucleocapsid protein shows that this relationship is also true of the more conserved central region of this protein and that the greatest divergence between Piry and Chandipura has occurred in two other regions of the nucleocapsid protein.

Familial hemolytic-uremic syndrome and homozygous factor H deficiency

Inherited hemolytic-uremic syndrome (HUS) is unusual. We report the occurrence of HUS in two siblings; one died at an early age while the other (the proband) has presented with three episodes of HUS since the age of 19 years. The finding of a persistently low serum C3 level in this patient led to a thorough evaluation of her complement cascade and a family investigation. The proband and her asymptomatic younger sister were found to have very low serum levels (5% of normal) of factor H, a regulatory protein of the alternative complement pathway. Both patients had low levels of serum C3, factor B, CH50 and VAH50, reflecting persistent alternative pathway activation. The father and mother both had half-normal serum factor H levels but an otherwise normal complement profile. Other members of the extended pedigree were also found to have half-normal serum factor H levels. In conclusion, in this family, factor H deficiency appears to be associated with HUS and is transmitted as an autosomal recessive trait. Persistent C3 hypocomplementemia in the setting of familial and/or recurrent HUS should be a clue to a possible inherited complement deficiency.

Induction of apoptosis in mouse [correction of rat] olfactory neuroepithelium by synaptic target ablation

The olfactory system provides a useful in vivo model for studying the influence of synaptic targets on the survival of relay neurones. The bipolar sensory neurones located in the olfactory mucosa project synaptically onto the ipsilateral olfactory bulb, and their survival depends on the integrity of this connection. We demonstrate here that the retrograde neuronal degeneration induced by olfactory bulb removal involves apoptosis. As revealed by typical nucleosome-sized fragmentations of the genomic DNA, the apoptosis rate reaches a maximum 32 h after bulbectomy. A transient c-fos mRNA accumulation was detected, peaking 16 h after bulbectomy, suggesting that c-fos is involved in the early steps of programmed cell death.

Structure-activity studies in E. coli strains on ochratoxin A (OTA) and its analogues implicate a genotoxic free radical and a cytotoxic thiol derivative as reactive metabolites

Ochratoxin A (OTA), its major metabolite in rodents, ochratoxin alpha, and seven structurally related substances were assayed for SOS DNA repair inducing activity in Escherichia coli strain PQ37. At concentrations of 0.1-4 mM, OTA, chloroxine, 5-chloro-8-quinolinol, 4-chloro-meta-cresol and chloroxylenol induced SOS DNA repair in the absence of an exogenous metabolic activation system. Ochratoxin B, ochratoxin alpha, 5-chlorosalicylic acid and citrinin were inactive, but all except ochratoxin alpha were cytotoxic. Thus, the presence of chlorine at C-5 appears to be one determinant of genotoxicity in these substances. Amino oxyacetic acid, an inhibitor of the cysteine conjugate beta-lyase, decreased the cytotoxicity of OTA but did not alter its genotoxic activity, suggesting the formation of a cytotoxic thiol-containing derivative. The mechanisms by which OTA and some of its active analogues induce SOS DNA repair activity was further investigated in E. coli PQ37 and in three derived strains (PQ300, OG100 and OG400), containing deletions within the oxy R regulon. The response in strain PQ37 was measured in the absence and presence of Trolox C, a water-soluble form of vitamin E. Trolox C completely quenched the genotoxicity of OTA, and the effect was similar in the mutant and wild-type strains. These results implicate an OTA-derived free radical rather than reduced oxygen species as genotoxic intermediate(s) in bacteria.

Transformation of primary chick-embryo fibroblasts by virally-expressed C-jun requires no mutation in the protein when a sufficient level of C-jun protein is reached

Proto-oncogene c-jun transforms primary chick embryo fibroblasts as a single gene when expressed from the replication competent retrovirus R (or RCAS). We have investigated whether transformation is caused by accumulating mutations within the proto-oncogene sequence during the retrotranscription process. c-jun coding sequences carried by three independently isolated R-cJUN viruses have been cloned and entirely sequenced. Two of these-were shown to carry no mutation demonstrating that deregulated expression of a normal c-Jun product is sufficient for transformation. On the contrary when expressed from non replicative Rneo vector lacking gag and pol sequences, the avian c-jun no longer transformed. This difference is correlated with weaker c-Jun accumulation in the second case. When expressed from the same Rneo vector, low level of v-Jun or of the heterologous mouse c-Jun still transform. Taken together, these data strongly suggest that a threshold level of c-Jun product is required for transformation and that this critical level can be lowered by mutations in c-jun or by the synthesis of an heterologous protein.