mTert induction in p21-positive cells counteracts capillary rarefaction and pulmonary emphysema

Lung diseases develop when telomeres shorten beyond a critical point. We constructed a mouse model in which the catalytic subunit of telomerase (mTert), or its catalytically inactive form (mTertCI), is expressed from the p21Cdkn1a locus. Expression of either TERT or TERTCI reduces global p21 levels in the lungs of aged mice, highlighting TERT non-canonical function. However, only TERT reduces accumulation of very short telomeres, oxidative damage, endothelial cell (ECs) senescence and senile emphysema in aged mice. Single-cell analysis of the lung reveals that p21 (and hence TERT) is expressed mainly in the capillary ECs. We report that a fraction of capillary ECs marked by CD34 and endowed with proliferative capacity declines drastically with age, and this is counteracted by TERT but not TERTCI. Consistently, only TERT counteracts decline of capillary density. Natural aging effects are confirmed using the experimental model of emphysema induced by VEGFR2 inhibition and chronic hypoxia. We conclude that catalytically active TERT prevents exhaustion of the putative CD34 + EC progenitors with age, thus protecting against capillary vessel loss and pulmonary emphysema.

Non-canonical telomere protection role of FOXO3a of human skeletal muscle cells regulated by the TRF2-redox axis

Telomeric repeat binding factor 2 (TRF2) binds to telomeres and protects chromosome ends against the DNA damage response and senescence. Although the expression of TRF2 is downregulated upon cellular senescence and in various aging tissues, including skeletal muscle tissues, very little is known about the contribution of this decline to aging. We previously showed that TRF2 loss in myofibers does not trigger telomere deprotection but mitochondrial dysfunction leading to an increased level of reactive oxygen species. We show here that this oxidative stress triggers the binding of FOXO3a to telomeres where it protects against ATM activation, revealing a previously unrecognized telomere protective function of FOXO3a, to the best of our knowledge. We further showed in transformed fibroblasts and myotubes that the telomere properties of FOXO3a are dependent on the C-terminal segment of its CR2 domain (CR2C) but independent of its Forkhead DNA binding domain and of its CR3 transactivation domain. We propose that these non-canonical properties of FOXO3a at telomeres play a role downstream of the mitochondrial signaling induced by TRF2 downregulation to regulate skeletal muscle homeostasis and aging.

OUP accepted manuscript

The shelterin protein complex is required for telomere protection in various eukaryotic organisms. In mammals, the shelterin subunit TRF2 is specialized in preventing ATM activation at telomeres and chromosome end fusion in somatic cells. Here, we demonstrate that the zebrafish ortholog of TRF2 (encoded by the terfa gene) is protecting against unwanted ATM activation genome-wide. The terfa-compromised fish develop a prominent and specific embryonic neurodevelopmental failure. The heterozygous fish survive to adulthood but exhibit a premature aging phenotype. The recovery from embryonic neurodevelopmental failure requires both ATM inhibition and transcriptional complementation of neural genes. Furthermore, restoring the expression of TRF2 in glial cells rescues the embryonic neurodevelopment phenotype. These results indicate that the shelterin subunit TRF2 evolved in zebrafish as a general factor of genome maintenance and transcriptional regulation that is required for proper neurodevelopment and normal aging. These findings uncover how TRF2 links development to aging by separate functions in gene expression regulation and genome stability control.

A 3D approach to model the taper of irregular tree stems: making plots biomass estimates comparable in tropical forests

In tropical forests, the high proportion of trees showing irregularities at the stem base complicates forest monitoring. For example, in the presence of buttresses, the height of the point of measurement (H_POM ) of the stem diameter (D_POM ) is raised from 1.3 m, the standard breast height, up to a regular part of the stem. While D_POM is the most important predictor for tree aboveground biomass (AGB) estimates, the lack of harmonized H_POM for irregular trees in forest inventory increases the uncertainty in plot-level AGB stock and stock change estimates. In this study, we gathered an original non-destructive three-dimensional (3D) data set collected with terrestrial laser scanning and close range terrestrial photogrammetry tools in three sites in central Africa. For the 228 irregularly shaped stems sampled, we developed a set of taper models to harmonize H_POM by predicting the equivalent diameter at breast height (DBH') from a D_POM measured at any height. We analyzed the effect of using DBH' on tree-level and plot-level AGB estimates. To do so, we used destructive AGB data for 140 trees and forest inventory data from eight 1-ha plots in the Republic of Congo. Our results showed that our best simple taper model predicts DBH' with a relative mean absolute error of 3.7% (R²  = 0.98) over a wide D_POM range of 17-249 cm. Based on destructive AGB data, we found that the AGB allometric model calibrated with harmonized H_POM data was more accurate than the conventional local and pantropical models. At the plot level, the comparison of AGB stock estimates with and without H_POM harmonization showed an increasing divergence with the increasing share of irregular stems (up to -15%). The harmonization procedure developed in this study could be implemented as a standard practice for AGB monitoring in tropical forests as no additional forest inventory measurements is required. This would probably lead to important revisions of the AGB stock estimates in regions having a large number of irregular tree stems and increase their carbon sink estimates. The growing use of three-dimensional (3D) data offers new opportunities to extend our approach and further develop general taper models in other tropical regions.

The Telomeric Protein TRF2 Regulates Replication Origin Activity within Pericentromeric Heterochromatin

Heterochromatic regions render the replication process particularly difficult due to the high level of chromatin compaction and the presence of repeated DNA sequences. In humans, replication through pericentromeric heterochromatin requires the binding of a complex formed by the telomeric factor TRF2 and the helicase RTEL1 in order to relieve topological barriers blocking fork progression. Since TRF2 is known to bind the Origin Replication Complex (ORC), we hypothesized that this factor could also play a role at the replication origins (ORI) of these heterochromatin regions. By performing DNA combing analysis, we found that the ORI density is higher within pericentromeric satellite DNA repeats than within bulk genomic DNA and decreased upon TRF2 downregulation. Moreover, we showed that TRF2 and ORC2 interact in pericentromeric DNA, providing a mechanism by which TRF2 is involved in ORI activity. Altogether, our findings reveal an essential role for TRF2 in pericentromeric heterochromatin replication by regulating both replication initiation and elongation.

P2RX7B is a new theranostic marker for lung adenocarcinoma patients

Rationale: The characterization of new theranostic biomarkers is crucial to improving the clinical outcome of patients with advanced lung cancer. Here, we aimed at characterizing the P2RX7 receptor, a positive modulator of the anti-tumor immune response, in patients with lung adenocarcinoma.

Methods: The expression of P2RX7 and its splice variants was analyzed by RT-qPCR using areas of tumor and non-tumor lung adenocarcinoma (LUAD) tissues on both immune and non-immune cells. The biological activity of P2RX7 was studied by flow cytometry using fluorescent dyes. Bi-molecular fluorescence complementation and confocal microscopy were used to assess the oligomerization of P2RX7. Tumor immune infiltrates were characterized by immunohistochemistry.

Results: Fifty-three patients with LUAD were evaluated. P2RX7A, and 3 alternative splice variants were expressed in LUAD tissues and expression was down regulated in tumor versus adjacent non-tumor tissues. The protein retained biological activity only in immune cells. The P2RX7B splice variant was differentially upregulated in immune cells (P < 0.001) of the tumor and strong evidence of oligomerization of P2RX7A and B was observed in the HEK expression model, which correlated with a default in the activity of P2RX7. Finally, LUAD patients with a high level of P2RX7B had non-inflamed tumors (P = 0.001).

Conclusion: Our findings identified P2RX7B as a new theranostic tool to restore functional P2RX7 activity and open alternative therapeutic opportunities to improve LUAD patient outcome.

Mitochondrial function in skeletal myofibers is controlled by a TRF2-SIRT3 axis over lifetime

Telomere shortening follows a developmentally regulated process that leads to replicative senescence of dividing cells. However, whether telomere changes are involved in postmitotic cell function and aging remains elusive. In this study, we discovered that the level of the TRF2 protein, a key telomere-capping protein, declines in human skeletal muscle over lifetime. In cultured human myotubes, TRF2 downregulation did not trigger telomere dysfunction, but suppressed expression of the mitochondrial Sirtuin 3 gene (SIRT3) leading to mitochondrial respiration dysfunction and increased levels of reactive oxygen species. Importantly, restoring the Sirt3 level in TRF2-compromised myotubes fully rescued mitochondrial functions. Finally, targeted ablation of the Terf2 gene in mouse skeletal muscle leads to mitochondrial dysfunction and sirt3 downregulation similarly to those of TRF2-compromised human myotubes. Altogether, these results reveal a TRF2-SIRT3 axis controlling muscle mitochondrial function. We propose that this axis connects developmentally regulated telomere changes to muscle redox metabolism.

TRF2-Mediated Control of Telomere DNA Topology as a Mechanism for Chromosome-End Protection

The shelterin proteins protect telomeres against activation of the DNA damage checkpoints and recombinational repair. We show here that a dimer of the shelterin subunit TRF2 wraps ∼ 90 bp of DNA through several lysine and arginine residues localized around its homodimerization domain. The expression of a wrapping-deficient TRF2 mutant, named Top-less, alters telomeric DNA topology, decreases the number of terminal loops (t-loops), and triggers the ATM checkpoint, while still protecting telomeres against non-homologous end joining (NHEJ). In Top-less cells, the protection against NHEJ is alleviated if the expression of the TRF2-interacting protein RAP1 is reduced. We conclude that a distinctive topological state of telomeric DNA, controlled by the TRF2-dependent DNA wrapping and linked to t-loop formation, inhibits both ATM activation and NHEJ. The presence of RAP1 at telomeres appears as a backup mechanism to prevent NHEJ when topology-mediated telomere protection is impaired.

Le projet BibliothEP : étude d’efficacité clinique d’une bibliothérapie de l’éjaculation précoce (EP)

Objectif

L’éjaculation précoce (EP) touche environ un homme sur cinq. Le projet BibliothEP (évaluation d’une bibliothérapie de l’EP) s’est fixé comme objectif d’élaborer un traitement à la fois efficace, simple, facile d’accès, bon marché, libre de toute toxicité et éventuellement applicable sans l’intrusion d’un tiers.

Méthode

L’étude s’est déroulée en deux phases. La première comprenait 120 participants souffrant d’EP. Un manuel concis (51 pages A5) d’auto-traitement cognitivo-comportemental de l’EP leur a été donné à lire, suite à quoi ils ont été comparés à 66 sujets laissés en liste d’attente. La seconde phase comparait 36 sujets ayant lu le manuel à 32 autres qui, en plus du manuel, recevaient un bref accompagnement (45 à 90 minutes) par un professionnel de la santé. Les accompagnants n’étaient pas spécialisés en thérapie sexuelle mais ont reçu une formation de 5 heures les habilitant à soutenir et faciliter le processus d’auto-traitement. Les paramètres évalués après traitement comprenaient la latence éjaculatoire auto-estimée, le sentiment de contrôle sur l’éjaculation, la satisfaction sexuelle, la détresse relative à la situation et l’impression subjective d’amélioration.

Résultats

Six mois après le traitement, tous les participants ont montré des améliorations significatives en comparaison des sujets laissés en liste d’attente. Ces améliorations persistaient à 12 mois. Elles étaient légèrement supérieures pour les participants ayant bénéficié d’une assistance. Des améliorations ont été trouvées pour toutes les formes du trouble mais l’intervention semble avoir été légèrement plus efficace lorsque l’EP était de sévérité modérée. Dans tous les cas, les améliorations du fonctionnement sexuel se sont accompagnées d’une amélioration des cognitions sexuelles.

Conclusions

Le rapport coût/efficacité de la bibliothérapie en fait un instrument thérapeutique idéal en première ligne. Il semble en outre possible de majorer l’efficacité de la formule en la doublant d’une assistance par un intervenant expressément formé à cette fin.

The prevalence of burnout among oncology professionals: oncologists are at risk of developing burnout

OBJECTIVE

International research shows that oncology staff suffers more from burnout than other healthcare professionals. Burnout is common among oncologists. The prevalence of emotional exhaustion, depersonalization, and low personal accomplishment appears to be significantly higher among physicians. Detecting burnout is highly relevant, because it affects the personal well-being and quality of life of the healthcare professional. A national study on the prevalence of burnout in oncology was never conducted in Flanders (Dutch-speaking part of Belgium).

METHODS

The Cédric Hèle institute spread anonymous questionnaires among 923 healthcare workers in oncology (physicians, social workers, psychologists, nurses, and specialist-nurses) in Flanders. The questionnaire consisted of two parts. The first part contained questions concerning demographic and job features. The second part included the Dutch version of the Maslach Burnout Inventory.

RESULTS

Five hundred and fifty subjects participated in the survey (response rate of 59.5%). Of the medical oncologists, 51.2% suffered from emotional exhaustion, 31.8% from depersonalization, and 6.8% from a lack of personal accomplishment. Multivariate analysis of variance suggested a significantly elevated level of emotional exhaustion and depersonalization in oncologists compared with other professionals. Logistic regression indicated that the following variables have predictive value on risk of burnout: gender, profession, and combining work in a university hospital with work in a private hospital.

CONCLUSION

The CHi research showed a significantly increased level of burnout-components in professionals working in oncology, especially in medical oncologists. These results should have an impact on the daily clinic of oncology, and could be guidance for further research.

TRF2 controls telomeric nucleosome organization in a cell cycle phase-dependent manner

Mammalian telomeres stabilize chromosome ends as a result of their assembly into a peculiar form of chromatin comprising a complex of non-histone proteins named shelterin. TRF2, one of the shelterin components, binds to the duplex part of telomeric DNA and is essential to fold the telomeric chromatin into a protective cap. Although most of the human telomeric DNA is organized into tightly spaced nucleosomes, their role in telomere protection and how they interplay with telomere-specific factors in telomere organization is still unclear. In this study we investigated whether TRF2 can regulate nucleosome assembly at telomeres.

By means of chromatin immunoprecipitation (ChIP) and Micrococcal Nuclease (MNase) mapping assay, we found that the density of telomeric nucleosomes in human cells was inversely proportional to the dosage of TRF2 at telomeres. This effect was not observed in the G1 phase of the cell cycle but appeared coincident of late or post-replicative events. Moreover, we showed that TRF2 overexpression altered nucleosome spacing at telomeres increasing internucleosomal distance. By means of an in vitro nucleosome assembly system containing purified histones and remodeling factors, we reproduced the short nucleosome spacing found in telomeric chromatin. Importantly, when in vitro assembly was performed in the presence of purified TRF2, nucleosome spacing on a telomeric DNA template increased, in agreement with in vivo MNase mapping.

Our results demonstrate that TRF2 negatively regulates the number of nucleosomes at human telomeres by a cell cycle-dependent mechanism that alters internucleosomal distance. These findings raise the intriguing possibility that telomere protection is mediated, at least in part, by the TRF2-dependent regulation of nucleosome organization.

TRF2 and apollo cooperate with topoisomerase 2alpha to protect human telomeres from replicative damage

Human telomeres are protected from DNA damage by a nucleoprotein complex that includes the repeat-binding factor TRF2. Here, we report that TRF2 regulates the 5' exonuclease activity of its binding partner, Apollo, a member of the metallo-beta-lactamase family that is required for telomere integrity during S phase. TRF2 and Apollo also suppress damage to engineered interstitial telomere repeat tracts that were inserted far away from chromosome ends. Genetic data indicate that DNA topoisomerase 2alpha acts in the same pathway of telomere protection as TRF2 and Apollo. Moreover, TRF2, which binds preferentially to positively supercoiled DNA substrates, together with Apollo, negatively regulates the amount of TOP1, TOP2alpha, and TOP2beta at telomeres. Our data are consistent with a model in which TRF2 and Apollo relieve topological stress during telomere replication. Our work also suggests that cellular senescence may be caused by topological problems that occur during the replication of the inner portion of telomeres.

Telomere uncapping during in vitro T-lymphocyte senescence

Normal lymphocytes represent examples of somatic cells that are able to induce telomerase activity when stimulated. As previously reported, we showed that, during lymphocyte long-term culture and repeated stimulations, the appearance of senescent cells is associated with telomere shortening and a progressive drop in telomerase activity. We further showed that this shortening preferentially occured at long telomeres and was interrupted at each stimulation by a transitory increase in telomere length. In agreement with the fact that telomere uncapping triggers lymphocyte senescence, we observed an increase in gamma-H2AX and 53BP1 foci as well as in the percentage of cells exhibiting DNA damage foci in telomeres. Such a DNA damage response may be related to the continuous increase of p16(ink4a) upon cell stimulation and cell aging. Remarkably, at each stimulation, the expression of shelterin genes, such as hTRF1, hTANK1, hTIN2, hPOT1 and hRAP1, was decreased. We propose that telomere dysfunction during lymphocyte senescence caused by iterative stimulations does not only result from an excessive telomere shortening, but also from a decrease in shelterin content. These observations may be relevant for T-cell biology and aging.

Telomere damage induced by the G-quadruplex ligand RHPS4 has an antitumor effect

Functional telomeres are required for the replicability of cancer cells. The G-rich strand of telomeric DNA can fold into a 4-stranded structure known as the G-quadruplex (G4), whose stabilization alters telomere function limiting cancer cell growth. Therefore, the G4 ligand RHPS4 may possess antitumor activity. Here, we show that RHPS4 triggers a rapid and potent DNA damage response at telomeres in human transformed fibroblasts and melanoma cells, characterized by the formation of several telomeric foci containing phosphorylated DNA damage response factors gamma-H2AX, RAD17, and 53BP1. This was dependent on DNA repair enzyme ATR, correlated with delocalization of the protective telomeric DNA-binding protein POT1, and was antagonized by overexpression of POT1 or TRF2. In mice, RHPS4 exerted its antitumor effect on xenografts of human tumor cells of different histotype by telomere injury and tumor cell apoptosis. Tumor inhibition was accompanied by a strong DNA damage response, and tumors overexpressing POT1 or TRF2 were resistant to RHPS4 treatment. These data provide evidence that RHPS4 is a telomere damage inducer and that telomere disruption selectively triggered in malignant cells results in a high therapeutic index in mice. They also define a functional link between telomere damage and antitumor activity and reveal the key role of telomere-protective factors TRF2 and POT1 in response to this anti-telomere strategy.

The Apollo 5′ Exonuclease Functions Together with TRF2 to Protect Telomeres from DNA Repair

A major issue in telomere research is to understand how the integrity of chromosome ends is preserved . The human telomeric protein TRF2 coordinates several pathways that prevent checkpoint activation and chromosome fusions. In this work, we identified hSNM1B, here named Apollo, as a novel TRF2-interacting factor. Interestingly, the N-terminal domain of Apollo is closely related to that of Artemis, a factor involved in V(D)J recombination and DNA repair. Both proteins belong to the beta-CASP metallo-beta-lactamase family of DNA caretaker proteins. Apollo appears preferentially localized at telomeres in a TRF2-dependent manner. Reduced levels of Apollo exacerbate the sensitivity of cells to TRF2 inhibition, resulting in severe growth defects and an increased number of telomere-induced DNA-damage foci and telomere fusions. Purified Apollo protein exhibits a 5'-to-3' DNA exonuclease activity. We conclude that Apollo is a novel component of the human telomeric complex and works together with TRF2 to protect chromosome termini from being recognized and processed as DNA damage. These findings unveil a previously undescribed telomere-protection mechanism involving a DNA 5'-to-3' exonuclease.

TRF2 inhibition promotes anchorage-independent growth of telomerase-positive human fibroblasts

Although telomere instability is observed in human tumors and is associated with the development of cancers in mice, it has yet to be established that it can contribute to the malignant transformation of human cells. We show here that in checkpoint-compromised telomerase-positive human fibroblasts an episode of TRF2 inhibition promotes heritable changes that increase the ability to grow in soft agar, but not tumor growth in nude mice. This transforming activity is associated to a burst of telomere instability but is independent of an altered control of telomere length. Moreover, it cannot be recapitulated by an increase in chromosome breaks induced by an exposure to gamma-radiations. Since it can be revealed in the context of telomerase-proficient human cells, telomere dysfunction might contribute to cancer progression even at late stages of the oncogenesis process, after the telomerase reactivation step.

Human telomeric position effect is determined by chromosomal context and telomeric chromatin integrity

We investigated the influence of telomere proximity and composition on the expression of an EGFP reporter gene in human cells. In transient transfection assays, telomeric DNA does not repress EGFP but rather slightly increases its expression. In contrast, in stable cell lines, the same reporter construct is repressed when inserted at a subtelomeric location. The telomeric repression is transiently alleviated by increasing the dosage of the TTAGGG repeat factor 1 (TRF1). Upon a prolongated treatment with trichostatin A, the derepression of the subtelomeric reporter gene correlates with the delocalization of HP1alpha and HP1beta. In contrast, treating the cells with 5 azacytidin, a demethylating agent, or with sirtinol, an inhibitor of the Sir2 family of deacetylase, has no apparent effect on telomeric repression. Overall, position effects at human chromosome ends are dependent on a specific higher-order organization of the telomeric chromatin. The possible involvement of HP1 isoforms is discussed.

Targeting assay to study the cis functions of human telomeric proteins: evidence for inhibition of telomerase by TRF1 and for activation of telomere degradation by TRF2

We investigated the control of telomere length by the human telomeric proteins TRF1 and TRF2. To this end, we established telomerase-positive cell lines in which the targeting of these telomeric proteins to specific telomeres could be induced. We demonstrate that their targeting leads to telomere shortening. This indicates that these proteins act in cis to repress telomere elongation. Inhibition of telomerase activity by a modified oligonucleotide did not further increase the pace of telomere erosion caused by TRF1 targeting, suggesting that telomerase itself is the target of TRF1 regulation. In contrast, TRF2 targeting and telomerase inhibition have additive effects. The possibility that TRF2 can activate a telomeric degradation pathway was directly tested in human primary cells that do not express telomerase. In these cells, overexpression of full-length TRF2 leads to an increased rate of telomere shortening.

Vital marking of articular chondrocytes by retroviral infection using green fluorescence protein

OBJECTIVE

One of the main open questions in chondrocyte transplantation is the fate of the implanted cells in vivo. We intended to establish prerequisites for such studies in animal models and to show the feasibility of this approach in rabbits. Isolated articular chondrocytes were retrovirally marked using green fluorescence protein (GFP) as a cell-specific marker in order to allow an in vivo follow-up of these cells.

METHODS

Chondrocytes from rabbits, sheep, cattle and humans were isolated and infected with murine leukemia virus-derived retroviruses carrying the GFP gene. The influence of the host range of three packaging cell lines (PA317, PT67, PG13), start cell concentrations, number of cell passages and number of infection cycles on the efficiency of infection was investigated. Stability of GFP expression was followed by FACS analysis, confocal imaging and fluorescence microscopy. For in vivo follow-up of GFP expression we used marked allogeneic chondrocyte populations grown on scaffold material and implanted them into full-thickness defects in knee joints of rabbits.

RESULTS

Retroviruses from all three packaging cell lines were able to infect rabbit and human chondrocytes, whereas only retroviruses released from PG13 cells were able to infect sheep and bovine chondrocytes efficiently. Optimization of the infection with these viruses resulted in efficiencies of 60-90% GFP-expressing chondrocytes. Populations of 100% marked chondrocytes were obtained by cell sorting. GFP expression stability of such marked chondrocyte populations was followed in monolayer culture and in 3-D culture on different scaffold materials. The expression of GFP was stable on all tested materials for at least 4 weeks. In monolayer culture GFP expression was stable for more than 8 months. In vivo, we observed stable GFP expression in the transplants during a four-week time course.

CONCLUSION

Retroviral GFP gene transfer led to long-term expression in chondrocytes from rabbits, sheep, cattle and humans. Transgene expression and the number of implanted chondrocytes remain stable for at least 4 weeks in vivo. This method permits a rapid monitoring of chondrocytes and provides a basis for following the fate of these cells in vivo.

Attitudes and knowledge about cancer pain in Flanders. The educational effect of workshops regarding pain and symptom control

Despite international agreements and recommendations regarding cancer pain therapy, the effectiveness of pain treatment is still a major problem even in Western countries. Part of the problem is that physicians and nurses often lack knowledge of methods for the assessment and treatment of cancer pain and may have many rigid beliefs and attitudes. This study investigated the misconceptions of physicians and nurses that play a role in the undertreatment of pain in Flanders (Belgium). We approached 197 health care workers who participated in the pain and symptom control education sessions organized by the Federation Palliative Care Flanders, and asked them to complete a questionnaire both before and after the sessions. The impact of the education sessions on their knowledge and beliefs regarding the management of cancer pain was substantial. Methods of reaching the target groups that do not feel the need for further education are discussed.

Plant CDC2 is not only targeted to the pre-prophase band, but also co-localizes with the spindle, phragmoplast, and chromosomes

A polyclonal antiserum against the p34cdc2 homologue of Arabidopsis thaliana, CDC2aAt, was used in parallel with a polyclonal antiserum against the PSTAIRE motif to study the subcellular localization of CDC2 during the cell cycle of isolated root tip cells of Medicago sativa. During interphase, CDC2 was located in the nucleus and in the cytoplasm. The cytoplasmic localization persisted during the complete cell cycle, whereas the nuclear signal disappeared at nuclear envelope breakdown. At the beginning of anaphase, the anti-CDC2aAt antibody transiently co-localized with condensed chromosomes. The chromosomal co-localization disappeared as anaphase continued and remained excluded from the separated chromosomes until cytokinesis, when CDC2 re-located to the newly forming nuclei. We also observed a co-localization of CDC2 with three microtubular structures, the pre-prophase band, the spindle, and the phragmoplast.

Sensitivity and positive predictive value of clinical signs of hypogonadism in elderly men

One hundred three ambulatory elderly men had serum free testosterone (FT) assessed as part of a study of bone loss. The FT was analyzed using radioimmunoassay. Each participant was questioned regarding the presence of erections adequate for sexual activity and the presence of sexual desire. Each was examined for decreased axillary and pubic hair. A FT of less than 9.0 pg/mL was found in eight subjects. The sensitivity of the clinical predictors as an indicator of a low FT value ranged from 43% to 86%, while positive predictive value ranged from 12% to 19%. The abnormal clinical signs and symptoms investigated in this study obviously have mechanisms in addition to hypogonadism. A history of adequate erections ruled out a low FT value in all but 1 of 44 cases.

Lack of association between free testosterone and bone density separate from age in elderly males

It is unclear what proportion of the variance in bone density in elderly males is accounted for by testosterone status. We studied 112 ambulatory, elderly volunteers (mean age 71.7 years) and determined free testosterone (FT), as well as bone density measurements by photon absorptiometry at multiple sites. Our studies of 35 of these subjects 4 years later included morning FT and dual energy X-ray absorptiometry. There were no significant correlations between FT and bone density at multiple scanning sites with the effects of age partialed out. We suspect that our inability to detect a significant effect of FT on bone density was related to the relative strength of other determinants of bone density, as well as to the fact that FT values are far more dynamic than bone density.

Identification of the cellular protein encoded by the human Wilms' tumor (WT1) gene

A putative tumor-suppressor gene (wt1) located at chromosome 11p13 and involved in Wilms' tumor development has recently been identified as a zinc finger polypeptide-encoding gene. The purpose of this study was to characterize the protein encoded by the human wt1 gene. The region spanning the entire zinc finger domain was amplified by polymerase chain reaction (PCR) and subcloned in the pATH 3 expression vector. Polyclonal antibodies against the fused TrpE-WT protein were raised. These antibodies immunoprecipitated a 49- to 51-kDa protein from hematopoietic tumor cells labeled in vivo with [35S]methionine. Subcellular fractionation and immunohistochemistry followed by confocal microscopy indicated that the Wilms' tumor gene product (WT1) is mainly localized within the nucleus.

Distribution of the rDNA and three classes of highly repetitive DNA in the chromatin of interphase nuclei of Arabidopsis thaliana

The distribution of the ribosomal RNA (rRNA) genes and three classes of highly repetitive DNA in the chromatin of interphase nuclei of Arabidopsis thaliana was studied for the first time through non-isotopic in situ hybridization and luminescence digital imaging microscopy. Each of the three classes of highly repetitive DNA exhibited a characteristic hybridization pattern, and one class was seen to be primarily localized on two chromocentres, which would allow it to distinguish a particular chromosome. The rDNA was consistently localized on the two largest chromocentres and on one or two smaller chromocentres. A limited number of nuclei exhibited more than four labelled chromocentres, indicative of either polypoidy or differential amplification of the rDNA. In nuclei where the nucleolus could be clearly observed, the nucleolar associated chromocentres (NACs) were seen to be labelled by the ribosomal DNA (rDNA) probe.