Stathmin and its phosphoprotein family: general properties, biochemical and functional interaction with tubulin

Stathmin, also referred to as Op18, is a ubiquitous cytosolic phosphoprotein, proposed to be a small regulatory protein and a relay integrating diverse intracellular signaling pathways involved in the control of cell proliferation, differentiation and activities. It interacts with several putative downstream target and/or partner proteins. One major action of stathmin is to interfere with microtubule dynamics, by inhibiting the formation of microtubules and/or favoring their depolymerization. Stathmin (S) interacts directly with soluble tubulin (T), which results in the formation of a T2S complex which sequesters free tubulin and therefore impedes microtubule formation. However, it has been also proposed that stathmin's action on microtubules might result from the direct promotion of catastrophes, which is still controversial. Phosphorylation of stathmin regulates its biological actions: it reduces its affinity for tubulin and hence its action on microtubule dynamics, which allows for example progression of cells through mitosis. Stathmin is also the generic element of a protein family including the neural proteins SCG10, SCLIP and RB3/RB3'/RB3". Interestingly, the stathmin-like domains of these proteins also possess a tubulin binding activity in vitro. In vivo, the transient expression of neural phosphoproteins of the stathmin family leads to their localization at Golgi membranes and, as previously described for stathmin and SCG10, to the depolymerization of interphasic microtubules. Altogether, the same mechanism for microtubule destabilization, that implies tubulin sequestration, is a common feature likely involved in the specific biological roles of each member of the stathmin family.

Impact of early versus late adherence to highly active antiretroviral therapy on immuno-virological response: a 3-year follow-up study

OBJECTIVE

To assess the impact of different patterns of adherence to highly active antiretroviral therapy (HAART), in particular, the relative impact of early and late adherence, on long-term immuno-virological response in HIV-infected individuals started on a protease inhibitor-containing regimen.

DESIGN

Clinical, immuno-virological and self-reported adherence data were collected at 4 (M4), 12 (M12), 20 (M20), 28 (M28) and 36 (M36) months after HAART initiation in the French APROCO cohort.

METHODS

A standardized self-administered questionnaire classified patients as non-adherent, moderately or highly adherent at each visit. Stable viral suppression at both M28 to M36, and a CD4 cell increase > 200 between M0 and M36 were used as outcome measures.

RESULTS

Of the 582 patients followed regularly through M36, 360 patients had complete adherence data. Although 59.2% were highly adherent at M4, only 25.8% maintained consistent high adherence throughout the follow-up. High adherence at M4 was independently associated with both stable viral suppression at M28-M36 [OR (95% CI): 2.8 (1.4-5.5)] and a CD4 cell increase > 200 during the same period [OR (95% CI): 3.9 (1.7-9.7)]. However, 'moderately adherent' patients between M12 and M36 had the same likelihood [OR (95% CI): 1.9 (1.1-3.2)] as patients who were always high adherent [OR (95% CI): 1.9 (1.1-3.2)] of achieving stable viral load suppression, relative to those who reported non-adherence episodes.

CONCLUSION

Optimizing adherence in the early months of treatment is crucial to ensure long-term immuno-virological high adherence during follow-up have a less negative impact. Priority should be given to interventions aimed to improve adherence in the early months of HAART.

Evaluation of buprenorphine maintenance treatment in a French cohort of HIV-infected injecting drug users

BACKGROUND

Buprenorphine was approved in France for treating opiate dependence in July 1995 and can be prescribed by general practitioners (GPs). Most studies assessing buprenorphine maintenance treatment (BMT) outcomes have taken place in GP settings. An evaluation of BMT outcomes in patients already followed for their HIV-infection could supply additional information about the changes in addictive practices in a non-GP setting.

METHODS

We assessed BMT discontinuations and the course of self-reported addictive behaviours and characteristics associated with buprenorphine-injection misuse in 114 HIV-infected patients on BMT who were followed in a hospital-based outpatient department.

RESULTS

The continuous series of follow-up visits at which these 114 patients reported regular buprenorphine prescriptions accounted for 237.5 person-years of observation, i.e. 475 follow-up visits. Of the 114 patients on BMT, 43% continued BMT throughout the follow-up, 40% stopped it, and results for 17% were not available either because they did not answer the self-administered questionnaire (5%) or because they were lost to follow-up (12%). Addictive behaviours declined but buprenorphine injection misuse remained stable. Depression measured by the CESD score (RR=1.04 95%CI [1.01-1.06]), cocaine use (RR=2.48 95%CI [1.31-4.68]) and alcohol consumption exceeding 4 alcohol units (AU) per day (RR=2.29, 95%CI [1.17-4.46]) were independently associated with buprenorphine injection misuse among stabilised BMT patients.

CONCLUSIONS

Despite the reduction in drug injection after starting BMT, buprenorphine injection misuse mainly involves patients with characteristics of severe addiction. Better monitoring of the illicit drug use patterns of patients on BMT may suggest new medical strategies for GPs to improve BMT outcomes.

Failure to maintain adherence to HAART in a cohort of French HIV-positive injecting drug users

The study, carried out in the French MANIF 2000 cohort of HIV positive patients contaminated through injecting drug use, assessed the impact of patients' sociodemographic and psychological characteristics, behaviors toward drug abuse, and antiretroviral treatment characteristics on the maintenance of adherence to HAART (highly active antiretroviral therapies). A total of 96 patients (30 men and 66 women), who were initially adherent at their first visit after HAART prescription, were considered for analysis. Among these 96 patients, 22 (22.9%) experienced adherence failure defined as a self-reported, non-adherence behavior at any visit before the 18th month of treatment. Logistic regression showed that lack of a stable relationship, active drug injection, and depression were independently associated with adherence failure. Patients' counseling for facilitating maintenance of adherence to HAART over time should focus on prevention of drug use, provision of social support and consider the potential impact of difficulties with treatment on psychological well-being.

[The stathmin-tubulin interaction and the regulation of the microtubule assembly]

Stathmin family proteins interact with tubulin and negatively regulate its assembly in microtubules. One stathmin molecule forms a complex with two alphabeta tubulin heterodimers in an interaction that is weakened upon stathmin phosphorylation. The X-ray structure of crystals of the complex reveals a head-to-tail arrangement of the two tubulins which are connected by a long stathmin alpha helix. By holding tubulins in a curved complex that is not incorporated in microtubules, stathmin lowers the pool of "assembly competent" tubulin. An alternate mechanism has been also proposed to account for the stathmin action in vivo; it involves a direct interaction of stathmin with microtubule (+) ends. More experiments are needed to evaluate the relative contribution of this alternative mechanism to the regulation of tubulin assembly by stathmin.

G. Triple Nucleoside Combination Zidovudine/Lamivudine/Abacavir versus Zidovudine/Lamivudine/Nelfinavir as First-Line Therapy in HIV-1-Infected Adults: A Randomized Trial

Objective

To compare the efficacy and safety of a triple nucleoside combination to a protease inhibitor-containing triple regimen as first-line antiretroviral therapy (ART) in HIV-1-infected patients.

Design

Open-label study in HIV-1-infected ART-naive adults, randomized to receive either Combivir® (lamivudine 150 mg/zidovudine 300 mg twice daily) + abacavir (300 mg twice daily), or Combivir® + nelfinavir (750 mg every 8 h) for 48 weeks. Plasma HIV-1 RNA, CD4 cell count and adverse events were assessed at baseline and weeks 4, 8, 16, 24, 32, 40 and 48.

Results

195 subjects (131 men, 64 women), median age 34 years, were randomized: 98 received combivir/abacavir and 97 combivir/nelfinavir. Baseline median plasma HIV-1 RNA was 4.2 log10 copies/ml [Interquartile range (IQR): 3.7-4.5.2] and 4.1 log10 copies/ml (IQR: 3.8–4.6), respectively. Baseline median CD4 cell count was 387 cells/mm3 (IQR: 194–501) and 449 cells/mm3 (IQR: 334–605), respectively. Nine patients (3 vs 6, respectively) did not start treatment or did not have any available efficacy data. At week 48, using the intent to treat analysis (switch/missing equals failure), plasma HIV-1 RNA was <50 copies/ml in 54/95 (57%) and 53/91 (58%) of subjects, respectively. Median CD4 increase was +110 and +120 cells/mm3, respectively. Possible hypersensitivity reactions to abacavir were reported in four subjects (4%).

Conclusion

The triple nucleoside combination combivir/abacavir is well tolerated as a first-line ART regimen in HIV-1-infected adults, with comparable antiviral activity to a nelfinavir-containing regimen at week 48.

Failure to maintain long-term adherence to highly active antiretroviral therapy: the role of lipodystrophy

In a sample of 277 patients included in the French APROCO cohort study who were initially adherent at follow-up visit 4 months after initiation of a protease inhibitor-containing regimen, 76.4% self-reported at least one lipodystrophy-related symptom and 30.0% failed to maintain adherence behaviour 20 months after enrolment. After multiple adjustment for other related factors, such as younger age, alcohol consumption and poor housing conditions, the number of self-reported lipodystrophy symptoms was independently associated with adherence failure.

Fostering health in the foster care maze

The fastest growing population of children in foster care today is quite young, and many of these children have significant health care needs. The General Accounting Office (GAO) reported that children in foster care "are among the most vulnerable individuals in the welfare population" (GAO, 1995, p. 1). Poverty, increased homelessness, substance abuse, and a rise in the incidence of persons with HIV all contribute to the problems faced by these children. The Caring Communities for Children in Foster Care Project, funded by the Maternal Child Health Bureau Integrated Services Medical Home Initiative with the American Academy of Pediatrics (AAP), investigated the availability of comprehensive health care services for children in foster care. The AAP recommends that pediatricians serve as the primary health care provider for children in foster care and also as consultants to child welfare agencies. Pediatric nurses play a crucial role in providing health care services to children in foster care. With an increased understanding of the potential physical and mental health care needs of children in foster care and the important role of foster parents, pediatric nurses can increase the likelihood of positive health outcomes for children in foster care.

Lipodystrophy in 685 HIV-1-treated patients: influence of antiretroviral treatment and immunovirological response

PURPOSE

To describe the clinical features in HIV-1-infected patients treated with protease inhibitors (PIs) or not, and to determine factors related to occurrence of lipodystrophy (LD).

METHOD

We performed a cross-sectional analysis of 685 treated HIV-1-infected patients that were routinely followed in 6 Paris hospital centers between January and May 1999. Demographic data, familial and personal vascular risk factors, history of antiretroviral treatment, HIV plasma viral load, CD4 cell count, and metabolic data were collected. Clinical examination was based on an assessment of changes in abdominal, dorso-cervical, and breast girth and wasting of the limbs, face, and skin as quoted by the clinician.

RESULTS

The mean age at inclusion in the study was 38 years; 29.5% were women. At study assessment, 77.5% of patients were PI-treated and 22.5% had never received a PI. LD was observed in 403 (58.8%) patients, of whom 340 were currently receiving a PI and 63 had never received a PI. More than half of the lipodystrophic patients had a mixed form (53.9%), while 25.3% were classified as exclusive lipoatrophic and 20.8% as exclusive hypertrophic. In multivariate analysis, older age, duration of antiretroviral treatment (ART), antiretroviral combinations including stavudine, antiretroviral combinations including a PI, AIDS status, and a low HIV RNA were independently associated with occurrence of LD.

CONCLUSION

LD is frequently observed in PI-treated patients, but it is also observed in patients receiving an ART regimen without PIs. Our study suggests different underlying mechanisms, because immunovirological response to treatment as well as certain therapies were linked to the occurrence of LD. This hypothesis would be best clarified in a large prospective cohort of naive patients.

Differential effect of two stathmin/Op18 phosphorylation mutants on Xenopus embryo development

Stathmin/Op18 destabilizes microtubules in vitro and regulates microtubule polymerization in vivo. Both a microtubule catastrophe-promoting activity and a tubulin sequestering activity were demonstrated for stathmin in vitro, and both could contribute to microtubule depolymerization in vivo. Stathmin activity can be turned down by extensive phosphorylation on its four phosphorylatable serines, and down-regulation of stathmin activity by phosphorylation is necessary for cells to proceed through mitosis. We show here that microinjection of a nonphosphorylatable Ser to Ala (4A) quadruple mutant in Xenopus two-cell stage embryos results in cell cleavage arrest in the injected blastomeres and aborted development, whereas injection of a pseudo-phosphorylated Ser to Glu quadruple mutant (4E) does not prevent normal development. Addition of these mutants to mitotic cytostatic factor-arrested extracts in which spindle assembly was induced led to a dramatic reduction of spindle size with 4A stathmin, and to a moderate increase with 4E stathmin, but both localized to spindle poles. Interestingly, the microtubule assembly-dependent phosphorylation of endogenous stathmin was abolished in the presence of 4A stathmin, but not of 4E stathmin. Altogether, this shows that the phosphorylation-mediated regulation of stathmin activity during the cell cycle is essential for early Xenopus embryonic development.

Stathmin family proteins display specific molecular and tubulin binding properties

Stathmin family phosphoproteins (stathmin, SCG10, SCLIP, and RB3/RB3'/RB3") are involved in signal transduction and regulation of microtubule dynamics. With the exception of stathmin, they are expressed exclusively in the nervous system, where they display different spatio-temporal and functional regulations and hence play at least partially distinct and possibly complementary roles in relation to the control of development, plasticity, and neuronal activities. At the molecular level, each possesses a specific "stathmin-like domain" and, with the exception of stathmin, various combinations of N-terminal extensions involved in their association with intracellular membrane compartments. We show here that each stathmin-like domain also displays specific biochemical and tubulin interaction properties. They are all able to sequester two alpha/beta tubulin heterodimers as revealed by their inhibitory action on tubulin polymerization and by gel filtration. However, they differ in the stabilities of the complexes formed as well as in their interaction kinetics with tubulin followed by surface plasmon resonance as follows: strong stability and slow kinetics for RB3; medium for SCG10, SCLIP, and stathmin; and weak stability and rapid kinetics for RB3'. These results suggest that the fine-tuning of their stathmin-like domains contributes to the specific functional roles of stathmin family proteins in the regulation of microtubule dynamics within the various cell types and subcellular compartments of the developing or mature nervous system.

Mortality in a cohort of HIV-infected adults started on a protease inhibitor-containing therapy: standardization to the general population

Death rates in the APROCO cohort of 1,157 HIV-1 infected adults starting for the first time a protease inhibitor-containing therapy were standardized to the 1996 French general population mortality rates stratified by age and gender. Median follow-up was 23 months and mortality rate was 2.2% person-years (95% confidence interval [CI] = 1.6-2.9). Overall mortality was 7.8 times higher than in the general population (95% CI = 5.7-10.4), 4.7 in men and 19.5 in women. Among the 144 patients considered complete responders, the death rate was 1.2% person-years (95% CI = 0.2-3.5) and mortality remained 5.1 times higher (95% CI = 1.0-14.9) than in the general population. Failure of treatment, long-term adverse effects, or less favorable socio-demographic status could explain these trends.

Stathmin/Op18 phosphorylation is regulated by microtubule assembly

Stathmin/Op 18 is a microtubule (MT) dynamics-regulating protein that has been shown to have both catastrophe-promoting and tubulin-sequestering activities. The level of stathmin/Op18 phosphorylation was proved both in vitro and in vivo to be important in modulating its MT-destabilizing activity. To understand the in vivo regulation of stathmin/Op18 activity, we investigated whether MT assembly itself could control phosphorylation of stathmin/Op18 and thus its MT-destabilizing activity. We found that MT nucleation by centrosomes from Xenopus sperm or somatic cells and MT assembly promoted by dimethyl sulfoxide or paclitaxel induced stathmin/Op18 hyperphosphorylation in Xenopus egg extracts, leading to new stathmin/Op18 isoforms phosphorylated on Ser 16. The MT-dependent phosphorylation of stathmin/Op18 took place in interphase extracts as well, and was also observed in somatic cells. We show that the MT-dependent phosphorylation of stathmin/Op18 on Ser 16 is mediated by an activity associated to the MTs, and that it is responsible for the stathmin/Op18 hyperphosphorylation reported to be induced by the addition of "mitotic chromatin." Our results suggest the existence of a positive feedback loop, which could represent a novel mechanism contributing to MT network control.

Rac/Cdc42 and p65PAK regulate the microtubule-destabilizing protein stathmin through phosphorylation at serine 16

We have identified a rapid protein phosphorylation event at residue serine 16 of stathmin using two-dimensional gel electrophoresis coupled to matrix-assisted laser desorption/ionization mass spectrometry in combination with post-source decay analysis, which is induced by the epidermal growth factor receptor. Phosphorylation is specifically mediated by the small GTPases Rac and Cdc42 and their common downstream target, the serine/threonine kinase p65PAK. Both GTPases have previously been shown to regulate the dynamics of actin polymerization. Because stathmin destabilizes microtubules, and this process is inhibited by phosphorylation at residue 16, Rac and Cdc42 can potentially regulate both F-actin and microtubule dynamics.

Expression of stathmin and SCG10 proteins in the olfactory neurogenesis during development and after lesion in the adulthood

Stathmin and SCG10 belong to a family of phosphoproteins associated to cell proliferation and differentiation. In the present study, we have analyzed immunocytochemically the distribution of these proteins during neurogenesis in the mouse olfactory system, from midgestation to adulthood. Data show that already at embryonic day 12, stathmin and SCG10 immunoreactivities were present in the olfactory and vomeronasal neurons, and their number increased greatly, colocalizing with neuronal specific tubulin, a marker of immature neurons. Later on up to adulthood, the distribution of stathmin and SCG10 became progressively restricted to a few immature receptor and chemosensory neurons. Significantly, in the olfactory epithelium, stathmin was seen in immature neurons and also in basal cells representing precursors of neuronal elements. Interestingly, before birth stathmin and SCG10 immunopositive cells were seen outside the olfactory epithelium, seemingly migrating toward the olfactory bulb. After regeneration in the adult following peripheral lesion of the olfactory epithelium, stathmin and SCG10 were again strongly expressed and generally colocalized with neuronal specific tubulin immunoreactivity. Overall these results indicate that stathmin and SCG10 are expressed in immature olfactory neurons as well as in the migrating cells generated from the olfactory epithelium, supporting the role of these proteins in neurogenesis and cell migration.

The 4 A X-ray structure of a tubulin:stathmin-like domain complex

Phosphoproteins of the stathmin family interact with the alphabeta tubulin heterodimer (tubulin) and hence interfere with microtubule dynamics. The structure of the complex of GDP-tubulin with the stathmin-like domain of the neural protein RB3 reveals a head-to-tail assembly of two tubulins with a 91-residue RB3 alpha helix in which each copy of an internal duplicated sequence interacts with a different tubulin. As a result of the relative orientations adopted by tubulins and by their alpha and beta subunits, the tubulin:RB3 complex forms a curved structure. The RB3 helix thus most likely prevents incorporation of tubulin into microtubules by holding it in an assembly with a curvature very similar to that of the depolymerization products of microtubules.

Specific Ser-Pro phosphorylation by the RNA-recognition motif containing kinase KIS

We present here a first appraisal of the phosphorylation site specificity of KIS (for 'kinase interacting with stathmin'), a novel mammalian kinase that has the unique feature among kinases to possess an RNP type RNA-recognition motif (RRM). In vitro kinase assays using various standard substrates revealed that KIS has a narrow specificity, with myelin basic protein (MBP) and synapsin I being the best in vitro substrates among those tested. Mass spectrometry and peptide sequencing allowed us to identify serine 164 of MBP as the unique site phosphorylated by KIS. Phosphorylation of synthetic peptides indicated the importance of the proline residue at position +1. We also identified a tryptic peptide of synapsin I phosphorylated by KIS and containing a phosphorylatable Ser-Pro motif. Altogether, our results suggest that KIS preferentially phosphorylates proline directed residues but has a specificity different from that of MAP kinases and cdks.

Probing the native structure of stathmin and its interaction domains with tubulin. Combined use of limited proteolysis, size exclusion chromatography, and mass spectrometry

Stathmin is a cytosoluble phosphoprotein proposed to be a regulatory relay integrating diverse intracellular signaling pathway. Its interaction with tubulin modulates microtubule dynamics by destabilization of assembled microtubules or inhibition of their polymerization from free tubulin. The aim of this study was to probe the native structure of stathmin and to delineate its minimal region able to interact with tubulin. Limited proteolysis of stathmin revealed four structured domains within the native protein, corresponding to amino acid sequences 22-81 (I), 95-113 (II), 113-128 (III), and 128-149 (IV), which allows us to propose stathmin folding hypotheses. Furthermore, stathmin proteolytic fragments were mixed to interact with tubulin, and those that retained affinity for tubulin were isolated by size exclusion chromatography and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results indicate that, to interact with tubulin, a stathmin fragment must span a minimal core region from residues 42 to 126, which interestingly corresponds to the predicted alpha-helical "interaction region" of stathmin. In addition, an interacting stathmin fragment must include a short N- or C-terminal extension. The functional significance of these interaction constrains is further validated by tubulin polymerization inhibition assays with fragments designed on the basis of the tubulin binding results. The present results will help to optimize further stathmin structural studies and to develop molecular tools to target its interaction with tubulin.

Overexpression of stathmin in breast carcinomas points out to highly proliferative tumours

We recently discovered that stathmin was overexpressed in a subgroup of human breast carcinomas. Stathmin is a cytosolic phosphoprotein proposed to act as a relay integrating diverse cell signalling pathways, notably during the control of cell growth and differentiation. It may also be considered as one of the key regulators of cell division for its ability to destabilize microtubules in a phosphorylation-dependent manner. To assess the significance of stathmin overexpression in breast cancer, we evaluated the correlation of stathmin expression, quantified by reverse transcription polymerase chain reaction, with several disease parameters in a large series of human primary breast cancer (n = 133), obtained in strictly followed up women, whose clinico-pathological data were fully available. In agreement with our preliminary survey, stathmin was found overexpressed in a subgroup of tumours (22%). In addition, overexpression was correlated to the loss of steroid receptors (oestrogen, P = 0.0006; progesterone, P = 0.008), and to the Scarff-Bloom-Richardson histopathological grade III (P= 0.002), this latter being ascribable to the mitotic index component (P= 0.02). Furthermore studies at the DNA level indicated that stathmin is overexpressed irrespective of its genomic status. Our findings raise important questions concerning the causes and consequences of stathmin overexpression, and the reasons of its inability to counteract cell proliferation in the overexpression group.

Ulip/CRMP proteins are recognized by autoantibodies in paraneoplastic neurological syndromes

Anti-CV2 autoantibodies have recently been discovered in patients with paraneoplastic neurological diseases (PND). These disorders are associated with neuronal degeneration, mediated by autoimmune processes, in patients with systemic cancer. Anti-CV2 autoantibodies recognize a brain protein of 66 kDa developmentally regulated and specifically expressed by a subpopulation of oligodendrocytes in the adult brain. Here, we demonstrate that anti-CV2 sera recognize several post-translationally modified forms of Ulip4/CRMP3, a member of a protein family related to the axonal guidance and homologous to the Unc-33 gene product in Caenorhabditis elegans. The sequence of the human Ulip4/CRMP3 was determined and the gene localized to chromosome 10q25.2-q26, a region mutated in glioblastomas and containing tumour suppressor genes. The identification of the Ulip/CRMP proteins as recognized by anti-CV2 sera should provide new insights into the role of Ulip/CRMPs in oligodendrocytes and into pathophysiology of PND.

Upregulation and redistribution of cadherins reveal specific glial and muscle cell phenotypes during wallerian degeneration and muscle denervation in the mouse

In the present work, we investigated the expression of cadherin mRNAs in the adult neuromuscular system either under normal conditions or following experimental neurotomy. Cadherin-6, a marker of Schwann cell precursors, was not expressed in the adult peripheral nerve, while M-cadherin, cadherin-11, and N-cadherin were expressed both by glial and conjunctive cells. Moreover, the three transcripts were transiently upregulated in the distal stump of neurotomized sciatic nerve during Wallerian degeneration: N-cadherin was abundant in myelinating Schwann cells during myelin degradation, while M-cadherin and cadherin-11 may be upregulated in proliferating Schwann cells. M-cadherin, cadherin-11, and N-cadherin were also detected in myofibres and endomysium of adult gastrocnemius muscle. Following neurotomy, cadherin-11 was only transiently increased in denervated myofibres, while M-cadherin was increased and sustained for at least 21 days postoperation. In contrast, N-cadherin was not upregulated in denervated myofibres. Thus, we defined here a combination of cadherins expressed in the adult nerve and muscle, and modulated during Wallerian degeneration and muscle denervation. The comparison of the expression pattern of this combination of cadherins to the one previously described during embryonic development shows that chronically denervated Schwann and muscle cells do not reverse to embryonic state (recapitulative hypothesis), but present specific phenotypic features.

[Prevalence of HIV infection in dialysis patients: results of a national multicenter study]

In order to determine the prevalence of HIV infection in french patients with end-stage renal disease (ESRD) on maintenance dialysis therapy, questionnaire forms were mailed out in february 1997 to the heads of the 260 dialysis facilities. We documented number of patients on maintenance dialysis therapy (hemo and peritoneal dialysis) and for HIV infected dialysis patients: age, gender, cause and duration of ESRD, known duration of HIV infection, risk factors for HIV infection, HBV and/or HCV infection, presence of clinical acquired immunodeficiency syndrome (AIDS), total CD4 count and treatment with antiretroviral agents. Questionnaire forms were returned from 98% of the dialysis facilities. As of february 1997 some 22,707 patients with ESRD were treated by renal replacement therapy, 19,947 by hemodialysis (HD) and 2760 by peritoneal dialysis (PD). 82 patients with ESRD and HIV infection were reported corresponding to 0.36% prevalence rate of all patients undergoing dialysis at the time specified. The 82 study subjects with ESRD and HIV infection received hemodialysis (79 patients) or peritoneal dialysis (3 patients) in 42 facilities. Forty seven patients were treated in Paris and suburbs and 9 in our own center. All 82 patients comprised 63% men and 47% women which included patients coming from Africa (37%), Caribbean and Oceania (28%), Europe (35%) of a mean age of 41.8 years. Modes of transmission were homobisexuals 15%, heterosexuals 31%, intravenous drug abusers 17%, blood transfusion 17% and unknown 20%. The mean duration of HIV infection was 96 months (range 12-168 months) and the mean duration of ESRD was 58 months (range 1-235 months). HIV associated nephropathy was established in 31%. AIDS was diagnosed in 25 patients. Seventy one percent of the patients were receiving an antiretroviral drug (tritherapy in 25% of cases). In conclusion HIV prevalence rate among French dialysis patients is low and focused in Paris and oversea. Sexual transmission is the most important HIV contamination but blood transfusion transmission remains greater than in general HIV population. Survival has improved compared with the survival rate reported in the 1980s.

Cellular and subcellular localization of stathmin during oocyte and preimplantation embryo development

Stathmin is a 19 kDa cytosolic phosphoprotein, proposed to act as a relay integrating diverse intracellular signaling pathways involved in regulation of cell proliferation, differentiation, and function. To gain further information about its significance during early development, we analyzed stathmin expression and subcellular localization in mouse oocytes and preimplantation embryos. RT-PCR analysis revealed a low expression of stathmin mRNA in unfertilized oocytes and a higher expression at the blastocyst stage. A fine cytoplasmic punctuate fluorescent immunoreactive stathmin pattern was detected in the oocyte, while it evolved toward an increasingly speckled pattern in the two-cell and later four- to eight-cell embryo, with even larger speckles at the morula stage. In blastocysts, stathmin immunoreactivity was fine and intense in inner cell mass cells, whereas it was low and variable in trophectodermal cells. Electron microscopic analysis allowed visualization with more detail of two types of stathmin immunolocalization: small clusters in the cytoplasm of oocytes and blastocyst cells, together with loosely arranged clusters around the outer membrane of cytoplasmic vesicles, corresponding to the immunofluorescent speckles in embryos until the morula stage. In conclusion, it appears from our results that maternal stathmin is accumulated in the oocyte and is relocalized within the oocyte and early preimplantation embryonic cell cytoplasm to interact with specific cytoplasmic membrane formations. Probably newly synthesized, embryonic stathmin is expressed in the blastocyst, where it is localized more uniformly in the cytoplasm mostly of inner cell mass (ICM) cells. These expression and localization patterns are probably related to the particular roles of stathmin at the successive steps of oocyte maturation and early embryonic development. They further support the proposed physiologic importance of stathmin in essential biologic regulation.