Retrospective clinical and genetic analysis of COL6-RD patients with a long-term follow-up at a single French center

Collagen type VI-related dystrophies (COL6-RD) are rare diseases with a wide phenotypic spectrum ranging from severe Ullrich's congenital muscular dystrophy Ullrich congenital muscular dystrophy to much milder Bethlem myopathy Both dominant and recessive forms of COL6-RD are caused by pathogenic variants in three collagen VI genes (COL6A1, COL6A2 and COL6A3). The prognosis of these diseases is variable and difficult to predict during early disease stages, especially since the genotype-phenotype correlation is not always clear. For this reason, studies with long-term follow-up of patients with genetically confirmed COL6-RD are still needed. In this study, we present phenotypic and genetic data from 25 patients (22 families) diagnosed with COL6-RD and followed at a single French center, in both adult and pediatric neurology departments. We describe three novel pathogenic variants and identify COL6A2:c.1970-9G>A as the most frequent variant in our series (29%). We also observe an accelerated progression of the disease in a subgroup of patients. This large series of rare disease patients provides essential information on phenotypic variability of COL6-RD patients as well as on frequency of pathogenic COL6A gene variants in Southern France, thus contributing to the phenotypic and genetic description of Collagen type VI-related dystrophies.

HINT1 neuropathy: Expanding the genotype and phenotype spectrum

Inherited peripheral neuropathy (IPN) is a heterogeneous group of disorders due to pathogenic variation in more than 100 genes. In 2012, the first cases of IPN associated with HINT1 pathogenic variations were described in 33 families sharing the same phenotype characterized by an axonal neuropathy with neuromyotonia and autosomal recessive inheritance (NMAN: OMIM #137200). Histidine Triad Nucleotide Binding Protein 1 regulates transcription, cell-cycle control, and is possibly involved in neuropsychiatric pathophysiology. Herein, we report seven French patients with NMAN identified by Next Generation Sequencing. We conducted a literature review and compared phenotypic and genotypic features with our cohort. We identified a new HINT1 pathogenic variation involved in NMAN: c.310G>C p.(Gly104Arg). This cohort is comparable with literature data regarding age of onset (7,4yo), neuronal involvement (sensorimotor 3/7 and motor pure 4/7), and skeletal abnormalities (scoliosis 3/7, feet anomalies 6/7). We expand the phenotypic spectrum of HINT1-related neuropathy by describing neurodevelopmental or psychiatric features in six out of seven individuals such as generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), mood disorder and attention deficit hyperactivity disorder (ADHD). However, only 3/128 previously described patients had neuropsychiatric symptomatology or neurodevelopmental disorder. These features could be part of HINT1-related disease, and we should further study the clinical phenotype of the patients.

Progenitor mast cells and tryptase in Q fever

Q fever is an infectious disease due to Coxiella burnetii. Following a primary-infection, C. burnetii may persist in some patients, leading to endocarditis and vascular infections. Mast cells (MCs), known for their role in allergic diseases, innate immunity and cardiac function, are produced by bone marrow, circulate as progenitors in the bloodstream and reach tissues for their maturation and activation. The latter may be estimated by measuring serum tryptase levels. We wondered if MC progenitors and tryptase were affected in Q fever. We showed a decrease in MC progenitor count in Q fever patients whereas serum tryptase levels were increased. Taken together, our results show alterations of MC numbers and activity in Q fever patients, suggesting that MC are involved in Q fever pathophysiology.

Extremely premature infants: How does death in the delivery room influence mortality rates in two level 3 centers in France?

OBJECTIVES

Mortality rates of very preterm infants may vary considerably between healthcare facilities depending on the neonates' place of inclusion in the cohort study. The objective of this study was to compare the mortality rates of live-born extremely preterm neonates observed in two French tertiary referral hospitals, taking into account the occurrence of neonatal death both in the delivery room and in the neonatal intensive care unit (NICU).

METHODS

Retrospective observational study including all pregnancy terminations, stillbirths and live-born infants within a 22- to 26-week ^0/6 gestational age range was registered by two French level 3 university centers between 2009 and 2013. The mortality rates were compared between the two centers according to two places of inclusion: either the delivery room or the NICU.

RESULTS

A total of 344 infants were born at center A and 160 infants were born at center B. Among the live-born neonates, the rates of neonatal death were similar in center A (54/125, 43.2%) and center B (33/69, 47.8%; P=0.54). However, neonatal death occurred significantly more often in the delivery room at center A (31/54, 57.4%) than at center B (6/33, 18.2%; P<0.001). Finally, the neonatal death rate of live-born very preterm neonates admitted to the NICU was significantly lower in center A (25/94, 26.6%) than in center B (27/63, 42.9%; P=0.03).

CONCLUSIONS

This study points out how the inclusion of deaths in the delivery room when comparing neonatal death rates can lead to a substantial bias in benchmarking studies. Center A and center B each endorsed one of the two models of preferential place of neonatal death (delivery room or NICU) detailed in European studies. The reasons behind the two different models and their impact on how parents perceive supporting their neonate need further investigation.

Claudin-1, miR-122 and apolipoprotein E transductions improve the permissivity of SNU-182, SNU-398 and SNU-449 hepatoma cells to hepatitis C virus

Hepatitis C virus (HCV) is a human hepatotropic virus, but many hepatoma cell lines are not permissive to this virus. In a previous study, we observed that SNU-182, SNU-398 and SNU-449 hepatoma cell lines were nonpermissive to HCV. To understand the nonpermissivity, we evaluated the ability of each cell line to support the different steps of HCV life cycle (entry, replication and production of infectious particles). Using retroviral pseudoparticles pseudotyped with HCV envelope proteins and recombinant HCV produced in cell culture, we observed that low level or absence of claudin-1 (CLDN1) expression limited the viral entry process in SNU-182 and SNU-398 cells, respectively. Our results also showed that supplementation of the three cell lines with miR-122 partly restored the replication of a JFH1 HCV replicon. Finally, we observed that expression of apolipoprotein E (ApoE) was very low or undetectable in the three cell lines and that its ectopic expression permits the production of infectious viral particles in SNU-182 and SNU-398 cells but not in SNU-449 cells. Nevertheless, the supplementation of SNU-182, SNU-398 and SNU-449 cells with CLDN1, miR-122 and ApoE was not sufficient to render these cells as permissive as HuH-7 cells. Thus, these cell lines could serve as cell culture models for functional studies on the role of CLDN1, miR-122 and ApoE in HCV life cycle but also for the identification of new restriction and/or dependency host factors essential for HCV infection.

[Termination of pregnancy without feticide: A French national survey]

PURPOSE

Termination of pregnancy without feticide (TOPWF) is poorly known in France and far less practiced than palliative care after term birth of a child having a lethal pathology. Few teams consider it and its practice remains confidential. This survey tries to describe it.

MATERIAL AND METHODS

A national survey was realized in 2014 using a questionnaire sent to 50 centers of prenatal diagnosis depending on a perinatal diagnosis center in France.

RESULTS

Thirty-one centers answered the questionnaire. Seven teams shared their experience of TOPWF after 22-24 weeks gestation (WG). This practice concerned fetuses affected by "lethal" pathologies. The absence of feticide followed a parental request or a proposal of the medical team, after individual discussion in a multidisciplinary meeting. All the children born alive after TOPWF benefited of palliative care. The 24 other centers having answered our investigation performed systematically the feticide beyond 22-24 WG. They so wished "to protect" the fetus, the parents and the nursing team. A majority of these teams faced parental demands of abstention of feticide but few of them answered it favorably.

CONCLUSION

A robust "palliative culture" seems essential to allow the nursing team to consider the development of TOPWF.

[Palliative care for patients with heart failure]

PURPOSE

Heart failure is a common disease and its progression to end-stage heart failure is responsible of high mortality. The aim of this retrospective study was to assess the access to integrated palliative care to the usual management, 6 months prior to their death, and especially during the last hospitalization.

PATIENTS AND METHODS

A retrospective study was performed in patients who died of heart failure in 2009 in two hospitals. The analysis was performed on 20 cases of each institution. The records of consecutive patients were included in an anti-chronological order from 31st December 2009.

RESULTS

For their last hospitalization, 37 patients (93%) were hospitalized in emergency. Within 3 days prior to death, the most frequent symptoms were dyspnea (n=33, 82%), and pain (n=30, 75%). Therapeutic most frequently used were oxygen (n=31, 77%) and analgesics (n=30, 75%). No patient was seen by a psychologist. The decision to limit treatment for comfort care was reported for 24 patients (60%) and the median of the average time between the decision and death was 2 days (Q1-Q3, 1-5 days).

CONCLUSION

Patients with terminal heart failure have many symptoms often requiring multidisciplinary care. This type of study relating practices shows that there is still a lot to do to integrate palliative care in the usual management of patients with heart failure.

Genetic recombination of the hepatitis C virus: clinical implications

Genetic recombination is a well-known feature of RNA viruses that plays a significant role in their evolution. Although recombination is well documented for Flaviviridae family viruses, the first natural recombinant strain of hepatitis C virus (HCV) was identified as recently as 2002. Since then, a few other natural inter-genotypic, intra-genotypic and intra-subtype recombinant HCV strains have been described. However, the frequency of recombination may have been underestimated because not all known HCV recombinants are screened for in routine practice. Furthermore, the choice of treatment regimen and its predictive outcome remain problematic as the therapeutic strategy for HCV infection is genotype dependent. HCV recombination also raises many questions concerning its mechanisms and effects on the epidemiological and physiopathological features of the virus. This review provides an update on recombinant HCV strains, the process that gives rise to recombinants and clinical implications of recombination.

[Chronic urticaria]

Chronic urticaria (CU) is a common disease of unknown origin. Its impact on the quality of life is significant. Antibodies to high affinity receptors expressed on mast cells and basophiles (FcepsilonRI) are found in 30% of cases and may be associated with more severe and prolonged symptoms. A wide variety of disorders can be associated with CU. However, in the absence of suggestive signs or symptoms, an extensive workup rarely permits the diagnosis of an underlying pathology. In this case, the work up should be minimal. The newer generation oral anti-histamines represent the first line treatment. In the refractory cases, other drugs may be considered but few controlled studies support their use.

[Pain management, let us be simple but efficient]

The occurrence of pain during the course of bronchial carcinoma is nearly inescapable and often constitutes the main symptom for patients and those close to them. While pain control is held to be a priority of care in cancerology in the future, this goal is not always reached due to insufficient implementation of recommendations, however widely accessible. Our aim is to present the different aspects of pain treatment through the details of both pharmacological and nonpharmacological means.

Genetic features of polioviruses isolated in Tunisia, 1991-2006

BACKGROUND

Genetic characterisation of polioviruses remains highly important even in countries where wild poliovirus circulation has been interrupted. Sequence data on representative wild strains from all geographical regions is required for surveillance purposes and surveillance for vaccine-related isolates with increased potential for transmissibility in humans should continue.

OBJECTIVE

To report the genetic characteristics of wild and vaccine-related polioviruses isolated in Tunisia from 1991 to 2006.

STUDY DESIGN

Wild isolates were sequenced in the VP1 genomic region and compared to each other. Vaccine-related isolates were assessed for genetic recombination by PCR/RFLP and sequence analysis of the 3D region. Recombinant viruses were assessed for genetic drift in the VP1 region.

RESULTS

The VP1 sequences of the last wild isolates, all from serotype3, showed 97.7-98.7% nucleotide homology. Nineteen percent of vaccine-related isolates were vaccine/vaccine intertypic recombinants. No recombinant with non-poliovirus enteroviruses was identified. Mutational differences in the VP1 sequences of recombinant viruses ranged from 0.0% to 0.7% indicating a limited replication period.

CONCLUSIONS

This study provides sequence data on wild polioviruses from Tunisia/North Africa and shows that in countries with continuous high vaccine coverage transmission of vaccine-related polioviruses is time-limited.

Hepatitis C Virus p7 membrane protein quasispecies variability in chronically infected patients treated with interferon and ribavirin, with or without amantadine

A clinical study was carried out to compare the response rate of two groups of non-responder (NR) hepatitis C virus (HCV) genotype 1 chronically infected patients treated with interferon and ribavirin, with or without amantadine. The viral load decreased more markedly in the group treated by tritherapy including amantadine, but the response rate at the end of treatment was not significantly different between bitherapy and tritherapy. As amantadine could have an antiviral effect on the ion channel activity of the p7 HCV protein, the p7 quasispecies was characterized by cloning and sequencing. Sequence data were analyzed to determine the pattern and significance of p7 genetic heterogeneity and a possible relationship with therapy. Subtype differences were confirmed between p7 HCV genotypes 1a and 1b, and quasispecies analysis showed a reduction of genetic diversity in subtype 1a, but not 1b, during tritherapy. However, the absence of changes at numerous positions, as well as the conservative changes at other positions, indicated the high conservation of the p7 structure. Residue His-17, proposed to interact with amantadine, was fully conserved in both subtypes 1a and 1b, independently of amantadine administration. In conclusion, although the analysis of the p7 sequences revealed a selective pressure during therapy, no specific residues appeared to be linked to the effect of amantadine on viral decline. These results suggest that the potential antiviral effect of amantadine might be non-specific and related to a reduction in endosomal acidification and therefore reduced viral entry of HCV via its pH-dependent pathway.

Effects of damage in the articular surface on the cartilage response to injurious compression in vitro

Macroscopic structural damage to the cartilage articular surface can occur due to slicing in surgery, cracking in mechanical trauma, or fibrillation in early stage osteoarthrosis. These alterations may render cartilage matrix and chondrocytes susceptible to subsequent mechanical injury and contribute to progression of degenerative disease. To examine this hypothesis, single 300 microm deep vertical slices were introduced across a diameter of the articular surface of osteochondral explant disks on day 6 after dissection. Then a single uniaxial unconfined ramp compression at 7 x 10(-5) or 7 x 10(-2) s(-1) strain rate to a peak stress of 3.5 or 14 MPa was applied on day 13 during which mechanical behavior was monitored. Effects of slices alone and together with compression were measured in terms of explant swelling and cell viability on days 10 and 17. Slicing alone induced tissue swelling without significant cell death, while compression alone induced cell death without significant tissue swelling. Under low strain rate loading, no differences in the response to injurious compression were found between sliced and unsliced explants. Under high strain rate loading, slicing rendered cartilage more easily compressible and appeared to slightly reduce compression-induced cell and matrix injury. Findings highlight microphysical factors important to cartilage mechanical injury, and suggest ways that macroscopic structural damage may accelerate or, in certain cases, possibly slow the progression of cartilage degeneration.

Microstructural Modeling of Collagen Network Mechanics and Interactions with the Proteoglycan Gel in Articular Cartilage

Cartilage matrix mechanical function is largely determined by interactions between the collagen fibrillar network and the proteoglycan gel. Although the molecular physics of these matrix constituents have been characterized and modern imaging methods are capable of localized measurement of molecular densities and orientation distributions, theoretical tools for using this information for prediction of cartilage mechanical behavior are lacking. We introduce a means to model collagen network contributions to cartilage mechanics based upon accessible microstructural information (fibril density and orientation distributions) and which self-consistently follows changes in microstructural geometry with matrix deformations. The interplay between the molecular physics of the collagen network and the proteoglycan gel is scaled up to determine matrix material properties, with features such as collagen fibril pre-stress in free-swelling cartilage emerging naturally and without introduction of ad hoc parameters. Methods are developed for theoretical treatment of the collagen network as a continuum-like distribution of fibrils, such that mechanical analysis of the network may be simplified by consideration of the spherical harmonic components of functions of the fibril orientation, strain, and stress distributions. Expressions for the collagen network contributions to matrix stress and stiffness tensors are derived, illustrating that only spherical harmonic components of orders 0 and 2 contribute to the stress, while orders 0, 2, and 4 contribute to the stiffness. Depth- and compression-dependent equilibrium mechanical properties of cartilage matrix are modeled, and advantages of the approach are illustrated by exploration of orientation and strain distributions of collagen fibrils in compressed cartilage. Results highlight collagen-proteoglycan interactions, especially for very small physiological strains where experimental data are relatively sparse. These methods for determining matrix mechanical properties from measurable quantities at the microscale (composition, structure, and molecular physics) may be useful for investigating cartilage structure-function relationships relevant to load-bearing, injury, and repair.

Prestrain decreases cartilage susceptibility to injury by ramp compression in vitro

BACKGROUND

Injurious mechanical loading of articular cartilage can be an initiating factor in the development of degenerative joint disease. The tissue response to compression depends on the loading conditions and matrix mechanical properties. The short-term loading history of cartilage can affect its water content and microstructural organization, and may thereby modify its susceptibility to injury. We therefore examined the role of prestrain on the response of articular cartilage to injurious compression.

METHODS

The full-thickness cartilage of bovine osteochondral explants was subjected to prestrains of 0, 5, 10, 25 or 50% before application of injurious ramp compression characterized by a strain rate of 7x10(-2) or 7x10(-3)s-1 and peak stress of 3.5 or 14 MPa. Effects of prestrain were evaluated in terms of fluid exudation, tissue mechanical stiffening, and the tissue response to injurious compression as characterized by macroscopic crack formation, cell viability and glycosaminoglycan release to culture media.

RESULTS

Macroscopic crack formation due to injurious compression decreased with increasing prestrain in association with lower cell mortality. Significantly decreased susceptibility to injury was already evident for 10% prestrain. In contrast, explant mechanical stiffness was unchanged up to 25% prestrain.

CONCLUSION

Findings demonstrate that compressive strains due to the short-term loading history of cartilage may strongly reduce its susceptibility to mechanical injury. Conversely, matrix swelling may render cartilage more vulnerable to injury. The cartilage response to injurious compression is therefore strongly influenced by matrix fluid content, and possibly also by other structural parameters such as collagen fiber orientation.

[Anaphylaxis: initial management]

Anaphylaxis is an immediate systemic reaction caused by an external agent. Its initial management depends on the severity of the reaction. In case of benign to moderate reaction, anti-histamine and steroid treatment are sufficient to control the process, and management is ambulatory. A severe reaction (hypotension, dyspnea) can be life threatening and adrenalin administration by the intramuscular route is indicated. In this case, it is advocated to observe the evolution for 24 hours in the hospital and the patient should be prescribed adrenaline auto-injectors. It is recommended that individuals who have experienced anaphylaxis should receive consultation from an allergist regarding diagnosis, prevention and treatment.

[Bronchial erosion of mediastinal lymphadenopathy associates with Hodgkin's disease]

INTRODUCTION

Erosion of mediastinal adenopathy into the bronchial tree is classically associated with tuberculosis. We describe two cases of of such bronchial erosion with Hodgkin's disease.

CASE REPORT

The first case was of a seventy-year old man with a history of pulmonary silicosis. A sub-carenal mass was identified during investigation of chronic cough. The bronchoscopy revealed an inflammatory stenosis due to Hodgkin's disease. The second case was of a thirteen-year old child whose Hodgkin's disease was thought to be in remission following treatment. The erosion of mediastinal adenopathy into the main left bronchus produced complete left pulmonary atalectasis, which required endobronchial stenting.

CONCLUSIONS

In both cases, rigid bronchoscopy provided a histological diagnosis with diagnosis of Hodgkin's disease in the first case, and identification of recurrence in the other one. These cases are unusual. Such complications are usually complications of radiotherapy. Classically, erosion of mediastinal adenopathy into the bronchial tree is tuberculous in origin but they can be neoplasic.

Short-term changes in cell and matrix damage following mechanical injury of articular cartilage explants and modelling of microphysical mediators

The short-term responses of articular cartilage to mechanical injury have important implications for prevention and treatment of degenerative disease. Cell and matrix responses were monitored for 11 days following injurious compression of cartilage in osteochondral explants. Injury was applied as a single ramp compression to 14 MPa peak stress at one of three strain rates: 7 x 10(-1), 7 x 10(-3) or 7 x 10(-5) s(-1). Responses were quantified in terms of the appearance of macroscopic matrix cracks, changes in cell viability, and changes in cartilage wet weights. Loading at the highest strain rate resulted in acute cell death near the superficial zone in association with cracks, followed over the 11 days after compression by a gradual increase in cell death and loss of demarcation between matrix zones containing viable versus nonviable cells. In contrast, loading at the lowest strain rate resulted in more severe, nearly full-depth cell death acutely, but with no apparent worsening over the 11 days following compression. Between days 4 and 11, all mechanically injured explants significantly increased in wet weight, suggesting loss of matrix mechanical integrity independent of compression strain rate. Results demonstrate that short-term responses of cartilage depend upon the biomechanical characteristics of injurious loading, and suggest multiple independent pathways of mechanically-induced cell death and matrix degradation. Modifications to an existing fiber-reinforced poroelastic finite element model were introduced and the model was used for data interpretation and identification of microphysical events involved in cell and matrix injury. The model performed reasonably well at the slower strain rates and exhibited some capacity for anticipating the formation of superficial cracks during injurious loading. However, several improvements appear to be necessary before such a model could reliably be used to draw upon in vitro experimental results for prediction of injurious loading situations in vivo.

Epidemiological and quantitative study of GBV-C infection in french polytransfused children

From 1999 to 2002, 246 serum samples taken from polytransfused children were tested for the presence of GB virus C (GBV-C) RNA using a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay. This assay was based on the TaqMan technology and allowed viral load determination in infected children with a dynamic range from 10(3) to 10(7) genome equivalent (gEq) copies/ml. The limit of detection was estimated to 619 gEq copies/ml with a > or = 95% probability of a positive result. Thirty five sera were found to be GBV-C RNA positive, corresponding to a prevalence of GBV-C of 14.2%. The mean viral load was high, i.e., 6 +/- 1.4 log (range 3.22-7.42) gEq copies/ml, but low viral loads were also detected. Sequencing of the 5'-untranslated region (UTR) identified a majority of genotype 2 strains (82%) distributed into two subtypes, 88.5% genotype 2a and 11.5% genotype 2b. In conclusion, GBV-C active infection is very frequent in exposed populations such as polytransfused children. GBV-C RNA quantitation using real-time assay may be useful for diagnosis and follow-up of the natural history of GBV-C infection.

[Isoniazid-induced pleuro-pericarditis]

We report a case of pleuro-pericarditis related to administration of isoniazid. Drug-induced lupus is well known; we recall the principle clinical, biological and immunological characteristics.

Two cases of 'asthma' revealing a diverticulum of Kommerell

Among embryonic aortic vascular malformations, persistence of a right aortic arch and aberrant left subclavian artery associated with a diverticulum of Kommerell is rare, and is estimated to occur in 0.1% of the general population. We report two cases of diverticulum of Kommerell in which tracheal compression due to the vascular ring induced respiratory symptoms such as asthmatic dyspnoea. This reminds us that at least a chest X-ray should be performed in newly diagnosed asthmatic patients, focusing on the trachea and upper mediastinum. In case of vascular abnormality, angiography and magnetic resonance are the best investigations to define the abnormal anatomy and guide surgery.

Nine novel mutations in maturity-onset diabetes of the young (MODY) candidate genes in 22 Spanish families

The aims of this study were to estimate the prevalence of major maturity-onset diabetes of the young (MODY) subtypes in Spanish MODY families and to analyze genotype-phenotype correlations. Twenty-two unrelated pediatric MODY patients and 97 relatives were screened for mutations in the coding region of the glucokinase (GCK), hepatic nuclear factor- HNF-1alpha and HNF4alpha genes using PCR-single strand conformation polymorphism and/or direct sequencing. In families carrying GCK mutations, the influence of genetic defects on fetal growth was investigated by comparing the birth weights of 32 offspring discordant for the mutations. Mutations in MODY genes were identified in 64% of the families. GCK/MODY2 mutations were the most frequently found, in 41%: seven novel (R369P, S411F, M298K, C252Y, Y108C, A188E, and S383L) and 2 already described mutations. Four pedigrees (18%) harbored mutations in the HNF-1alpha/MODY3 gene, including a previously unreported change (R271G). One family (4%) carried a novel mutation in the HNF-4alpha gene (IVS5-2delA), representing the first report of a MODY1 pedigree in the Spanish population. The age at diagnosis was prepubertal in MODY2 index patients and pubertal in MODY3 patients. Overt diabetes was rare in MODY2 and was invariably present in MODY3 index patients. Chronic complications of diabetes were absent in the MODY2 population and were present in more than 40% of all relatives of MODY3. Birth weight was lower in the presence of a GCK fetal mutation when the mutation was of paternal origin. The MODY1 patient was diagnosed at 15 yr of age. She developed intermittent microalbuminuria despite good metabolic control, and severe late-onset complications were common within her family. Mutations in the GCK/MODY2 gene are the most common cause of MODY in our population as recruited from pediatric and adolescent index patients. The inheritance of GCK defects by the fetus results in a reduction of birth weight. Clinical expression of MODY3 and MODY1 mutations, the second and third groups of defects found, was more severe, including the frequent development of chronic complications.

Static compression of articular cartilage can reduce solute diffusivity and partitioning: implications for the chondrocyte biological response

Chondrocytes depend upon solute transport within the avascular extracellular matrix of adult articular cartilage for many of their biological activities. Alterations to bioactive solute transport may, therefore, represent a mechanism by which cartilage compression is transduced into cellular metabolic responses. We investigated the effects of cartilage static compression on diffusivity and partitioning of a range of model solutes including dextrans of molecular weights 3 and 40 kDa, and tetramethylrhodamine (a 430 Da fluorophore). New fluorescence methods were developed for real-time visualization and measurement of transport within compressed cartilage explants. Experimental design allowed for multiple measurements on individual explants at different compression levels in order to minimize confounding influences of compositional variations. Results demonstrate that physiological levels of static compression may significantly decrease solute diffusivity and partitioning in cartilage. Effects of compression were most dramatic for the relatively high molecular weight solutes. For 40 kDa dextran, diffusivity decreased significantly (p<0.01) between 8% and 23% compression, while partitioning of 3 and 40 kDa dextran decreased significantly (p<0.01) between free-swelling conditions and 8% compression. Since diffusivity and partitioning can influence pericellular concentrations of bioactive solutes, these observations support a role for perturbations to solute transport in mediating the cartilage biological response to compression.

Transcriptional repression by Suppressor of Hairless involves the binding of a Hairless-dCtBP complex in Drosophila

Notch is the receptor for a conserved signaling pathway that regulates numerous cell fate decisions during development [1]. Signal transduction involves the presenilin-dependent intracellular processing of Notch and the nuclear translocation of the intracellular domain of Notch, NICD [2-6]. NICD associates with Suppressor of Hairless [Su(H)], a DNA binding protein, and Mastermind (Mam), a transcriptional coactivator [7-9]. In the absence of Notch signaling, Su(H) acts as a transcriptional repressor [10, 11]. Repression by Su(H) is relieved by the activation of Notch [12-16]. In the Drosophila embryo, this transcriptional switch from repression to activation is important for patterning the expression of the single-minded (sim) gene along the dorsoventral axis [12]. Here, we investigate the mechanisms by which Su(H) inhibits the expression of Notch target genes in Drosophila. We show that Hairless, an antagonist of Notch signaling [17-19], is required to repress the transcription of the sim gene. Hairless forms a DNA-bound complex with Su(H). Furthermore, it directly binds the Drosophila C-terminal Binding Protein (dCtBP), which acts as a transcriptional corepressor. The dCtBP binding motif of Hairless is essential for the function of Hairless in vivo. We propose that Hairless mediates transcriptional repression by Su(H) via the recruitment of dCtBP.

Towards the proteome of the rhodopsin-bearing post-Golgi compartment of retinal photoreceptor cells

Polarized sorting of rhodopsin in retinal rod photoreceptor cells is mediated by post-Golgi carrier membranes that bud from the trans-Golgi network and fuse with the specialized domain of the plasma membrane in the rod inner segment. The identity of the majority of the resident proteins of this organelle still remains elusive, despite multifaceted approaches to study this compartment. In the present study we have taken a proteomic approach to the analysis of the post-Golgi carriers. First, we modified the previously established fractionation protocols in order to achieve greater purity of the isolated membranes. Specifically, the new fractionation scheme depleted the post-Golgi fraction of cytosolic proteins that were the most abundant contaminants complicating analysis of two-dimensional (2-D) gel profiles in our previous preparations. The isolated membranes were subjected to 2-D gel electrophoresis, immunoblotting and microsequencing. This analysis showed that the improved subcellular fractionation yielded a fraction highly enriched in rhodopsin-bearing post-Golgi carrier membranes. Two-dimensional mapping revealed 29 proteins that are preferentially found in this fraction and therefore represent candidates for post-Golgi membrane-specific proteins. This preparation of rhodopsin-bearing post-Golgi carriers is a first step towards the proteomics of this important organelle.

Repression by suppressor of hairless and activation by Notch are required to define a single row of single-minded expressing cells in the Drosophila embryo

Notch signal transduction appears to involve the ligand-induced intracellular processing of Notch, and the formation of a processed Notch-Suppressor of Hairless complex that binds DNA and activates the transcription of Notch target genes. This suggests that loss of either Notch or Su(H) activities should lead to similar cell fate changes. However, previous data indicate that, in the Drosophila blastoderm embryo, mesectoderm specification requires Notch but not Su(H) activity. The determination of the mesectodermal fate is specified by Single-minded (Sim), a transcription factor expressed in a single row of cells abutting the mesoderm. The molecular mechanisms by which the dorsoventral gradient of nuclear Dorsal establishes the single-cell wide territory of sim expression are not fully understood. We have found that Notch activity is required for sim expression in cellularizing embryos. In contrast, at this stage, Su(H) has a dual function. Su(H) activity was required to up-regulate sim expression in the mesectoderm, and to prevent the ectopic expression of sim dorsally in the neuroectoderm. We have shown that repression of sim transcription by Su(H) is direct and independent of Notch activity. Conversely, activation of sim transcription by Notch requires the Su(H)-binding sites. Thus, Notch signalling appears to relieve the repression exerted by Su(H) and to up-regulate sim transcription in the mesectoderm. We propose a model in which repression by Su(H) and derepression by Notch are essential to allow for the definition of a single row of mesectodermal cells in the blastoderm embryo.

Occurrence of an HIV-1 gp160 endoproteolytic activity in low-density vesicles and evidence for a distinct density distribution from endogenously expressed furin and PC7/LPC convertases

Human immunodeficiency virus (HIV) glycoprotein (gp) 160 processing by host cell proteinases is an essential step for viral fusion and infectivity. We have identified a rat liver subcellular fraction which specifically processes gp160 into gp120 and gp41. Using equilibration of microsomes in sucrose gradients, the gp160 cleavage activity was associated with particles equilibrating at low densities, well-separated from the endoplasmic reticulum, cis-Golgi network, Golgi stacks, lysosomes and plasma membrane. Its density distribution was compatible with light secretory vesicles derived from the trans-Golgi network (TGN) or to endosomes, but association with endosomes was not supported by free flow electrophoresis. Although furin and pro-protein convertase (PC) 7/LPC have been proposed as the major gp160 processing convertases, the rat liver microsomal gp160 processing activity was essentially resolved from furin and only partially overlapped PC7/LPC. These data suggest that proteinase(s) other than furin and PC7/LPC, presumably located in TGN-derived vesicles, may participate in the gp160 processing into gp120 and gp41.

Search for DNA sequence variations using a MutS-based technology

The search for DNA sequence variations (DSV) is emphasized with genetic studies of a large number of multifactorial diseases. Saturation of regions of interest with diallelic polymorphisms will be an essential step to pinpoint, through association studies, predisposing genes. We have developed a solid-phase method based on the ability of mismatch binding protein MutS to recognize single nucleotide mismatches. This approach was applied to the study of 83 sequence-tagged sites (STSs) extracted from an eight centimorgans (cM) chromosome 21 region. One-third of tested STSs were found to be polymorphic leading to a frequency of one DSV every 822 base pairs (bp). Sequencing of analyzed STSs showed the high reliability of the MutS-based technology for mismatches up to 2 bp in DNA fragments ranging in size from 200 bp to 1 kilobase (kb). The entire assay which is performed in a solid-phase format without the need of electrophoresis or sequencing, will provide an efficient tool for new polymorphism detection.

[Signalling by Notch family receptors]

From nematode to man, the transmembrane receptors of the Notch family act throughout embryonic and post-embryonic development to regulate the acquisition and/or maintenance of specific differentiative states. We will review here our current state of knowledge on Notch receptors structure and signalling activity.