Human SFI1 and Centrin form a complex critical for centriole architecture and ciliogenesis

Over the course of evolution, the centrosome function has been conserved in most eukaryotes, but its core architecture has evolved differently in some clades, with the presence of centrioles in humans and a spindle pole body (SPB) in yeast. Similarly, the composition of these two core elements has diverged, with the exception of Centrin and SFI1, which form a complex in yeast to initiate SPB duplication. However, it remains unclear whether this complex exists at centrioles and whether its function has been conserved. Here, using expansion microscopy, we demonstrate that human SFI1 is a centriolar protein that associates with a pool of Centrin at the distal end of the centriole. We also find that both proteins are recruited early during procentriole assembly and that depletion of SFI1 results in the loss of the distal pool of Centrin, without altering centriole duplication. Instead, we show that SFI1/Centrin complex is essential for centriolar architecture, CEP164 distribution, and CP110 removal during ciliogenesis. Together, our work reveals a conserved SFI1/Centrin module displaying divergent functions between mammals and yeast.

Septin filament compaction into rings requires the anillin Mid2 and contractile ring constriction

Septin filaments assemble into high-order molecular structures that associate with membranes, acting as diffusion barriers and scaffold proteins crucial for many cellular processes. How septin filaments organize in such structures is still not understood. Here, we used fission yeast to explore septin filament organization during cell division and its cell cycle regulation. Live-imaging and polarization microscopy analysis uncovered that septin filaments are initially recruited as a diffuse meshwork surrounding the acto-myosin contractile ring (CR) in anaphase, which undergoes compaction into two rings when CR constriction is initiated. We found that the anillin-like protein Mid2 is necessary to promote this compaction step, possibly acting as a bundler for septin filaments. Moreover, Mid2-driven septin compaction requires inputs from the septation initiation network as well as CR constriction and the β(1,3)-glucan synthase Bgs1. This work highlights that anillin-mediated septin ring assembly is under strict cell cycle control.

Kinesin-14 family proteins and microtubule dynamics define S. pombe mitotic and meiotic spindle assembly, and elongation

To segregate the chromosomes faithfully during cell division, cells assemble a spindle that captures the kinetochores and pulls them towards opposite poles. Proper spindle function requires correct interplay between microtubule motors and non-motor proteins. Defects in spindle assembly or changes in spindle dynamics are associated with diseases, such as cancer or developmental disorders. Here, we compared mitotic and meiotic spindles in fission yeast. We show that, even though mitotic and meiotic spindles underwent the typical three phases of spindle elongation, they have distinct features. We found that the relative concentration of the kinesin-14 family protein Pkl1 is decreased in meiosis I compared to mitosis, while the concentration of the kinesin-5 family protein Cut7 remains constant. We identified the second kinesin-14 family protein Klp2 and microtubule dynamics as factors necessary for proper meiotic spindle assembly. This work defines the differences between mitotic and meiotic spindles in fission yeast Schizosaccharomyces pombe, and provides prospect for future comparative studies.This article has an associated First Person interview with the first author of the paper.

Increasing ergosterol levels delays formin-dependent assembly of F-actin cables and disrupts division plane positioning in fission yeast

In most eukaryotes, cytokinesis is mediated by the constriction of a contractile acto-myosin ring (CR), which promotes the ingression of the cleavage furrow. Many components of the CR interact with plasma membrane lipids suggesting that lipids may regulate CR assembly and function. Although there is clear evidence that phosphoinositides play an important role in cytokinesis, much less is known about the role of sterols in this process. Here, we studied how sterols influence division plane positioning and CR assembly in fission yeast. We show that increasing ergosterol levels in the plasma membrane blocks the assembly of F-actin cables from cytokinetic precursor nodes, preventing their compaction into a ring. Abnormal F-actin cables form after a delay, leading to randomly placed septa. Since the formin Cdc12 was detected on cytokinetic precursors and the phenotype can be partially rescued by inhibiting the Arp2/3 complex, which competes with formins for F-actin nucleation, we propose that ergosterol may inhibit formin dependent assembly of F-actin cables from cytokinetic precursors.

Kinesin-6 regulates cell-size-dependent spindle elongation velocity to keep mitosis duration constant in fission yeast

The length of the mitotic spindle scales with cell size in a wide range of organisms during embryonic development. Interestingly, in C. elegans embryos, this goes along with temporal regulation: larger cells speed up spindle assembly and elongation. We demonstrate that, similarly in fission yeast, spindle length and spindle dynamics adjust to cell size, which allows to keep mitosis duration constant. Since prolongation of mitosis was shown to affect cell viability, this may resemble a mechanism to regulate mitosis duration. We further reveal how the velocity of spindle elongation is regulated: coupled to cell size, the amount of kinesin-6 Klp9 molecules increases, resulting in an acceleration of spindle elongation in anaphase B. In addition, the number of Klp9 binding sites to microtubules increases overproportionally to Klp9 molecules, suggesting that molecular crowding inversely correlates to cell size and might have an impact on spindle elongation velocity control.

SIN-Dependent Dissociation of the SAD Kinase Cdr2 from the Cell Cortex Resets the Division Plane

Proper division plane positioning is crucial for faithful chromosome segregation but also influences cell size, position, or fate [1]. In fission yeast, medial division is controlled through negative signaling by the cell tips during interphase and positive signaling by the centrally placed nucleus at mitotic entry [2-4]: the cell geometry network (CGN), controlled by the inhibitory cortical gradient of the DYRK kinase Pom1 emanating from the cell tips, first promotes the medial localization of cytokinetic ring precursors organized by the SAD kinase Cdr2 to pre-define the division plane [5-8]; then, massive nuclear export of the anillin-like protein Mid1 at mitosis entry confirms or readjusts the division plane according to nuclear position and triggers the assembly of a medial contractile ring [5, 9-11]. Strikingly, the Hippo-like septation initiation network (SIN) induces Cdr2 dissociation from cytokinetic precursors at this stage [12-14]. We show here that SIN-dependent phosphorylation of Cdr2 promotes its interaction with the 14-3-3 protein Rad24 that sequesters it in the cytoplasm during cell division. If this interaction is compromised, cytokinetic precursors are asymmetrically distributed in the cortex of newborn cells, leading to asymmetrical division if nuclear signaling is abolished. We conclude that, through this new function, the SIN resets the division plane in newborn cells to ensure medial division.

Molecular control of fission yeast cytokinesis

Cytokinesis gives rise to two independent daughter cells at the end of the cell division cycle. The fission yeast Schizosaccharomyces pombe has emerged as one of the most powerful systems to understand how cytokinesis is controlled molecularly. Like in most eukaryotes, fission yeast cytokinesis depends on an acto-myosin based contractile ring that assembles at the division site under the control of spatial cues that integrate information on cell geometry and the position of the mitotic apparatus. Cytokinetic events are also tightly coordinated with nuclear division by the cell cycle machinery. These spatial and temporal regulations ensure an equal cleavage of the cytoplasm and an accurate segregation of the genetic material in daughter cells. Although this model system has specificities, the basic mechanisms of contractile ring assembly and function deciphered in fission yeast are highly valuable to understand how cytokinesis is controlled in other organisms that rely on a contractile ring for cell division.

From Structure to Function: A Comprehensive Compendium of Tools to Unveil Protein Domains and Understand Their Role in Cytokinesis

Unveiling the function of a novel protein is a challenging task that requires careful experimental design. Yeast cytokinesis is a conserved process that involves modular structural and regulatory proteins. For such proteins, an important step is to identify their domains and structural organization. Here we briefly discuss a collection of methods commonly used for sequence alignment and prediction of protein structure that represent powerful tools for the identification homologous domains and design of structure-function approaches to test experimentally the function of multi-domain proteins such as those implicated in yeast cytokinesis.

Microtubule minus end motors kinesin-14 and dynein drive nuclear congression in parallel pathways

Long-term imaging via microfluidic chambers shows that two minus end–directed motors, dynein and Klp2, work in parallel at distinct subcellular structures to promote efficient nuclear congression.

Microtubules (MTs) and associated motors play a central role in nuclear migration, which is crucial for diverse biological functions including cell division, polarity, and sexual reproduction. In this paper, we report a dual mechanism underlying nuclear congression during fission yeast karyogamy upon mating of haploid cells. Using microfluidic chambers for long-term imaging, we captured the precise timing of nuclear congression and identified two minus end–directed motors operating in parallel in this process. Kinesin-14 Klp2 associated with MTs may cross-link and slide antiparallel MTs emanating from the two nuclei, whereas dynein accumulating at spindle pole bodies (SPBs) may pull MTs nucleated from the opposite SPB. Klp2-dependent nuclear congression proceeds at constant speed, whereas dynein accumulation results in an increase of nuclear velocity over time. Surprisingly, the light intermediate chain Dli1, but not dynactin, is required for this previously unknown function of dynein. We conclude that efficient nuclear congression depends on the cooperation of two minus end–directed motors.

Molecular control of the Wee1 regulatory pathway by the SAD kinase Cdr2

Cell growth and division are tightly coordinated to maintain cell size constant during successive cell cycles. In Schizosaccharomyces pombe, the SAD kinase Cdr2 regulates the cell size at division and the positioning of the division plane. Cdr2 forms nodes on the medial cortex containing factors that constitute an inhibitory pathway for Wee1. This pathway is regulated by polar gradients of the DYRK kinase Pom1, and involves a direct inhibitor of Wee1, the SAD kinase Cdr1. Cdr2 also interacts with the anillin Mid1, which defines the division plane, and with additional components of the medial cortical nodes, including Blt1, which participate in the mitotic-promoting and cytokinetic functions of nodes. Here, we show that the interaction of Cdr2 with Wee1 and Mid1 requires the UBA domain of Cdr2, which is necessary for its kinase activity. In contrast, Cdr1 associates with the C-terminus of Cdr2, which is composed of basic and KA-1 lipid-binding domains. Mid1 also interacts with the C-terminus of Cdr2 and might bridge the N- and C-terminal domains, whereas Blt1 associates with the central spacer region. We propose that the association of Cdr2 effectors with different domains might constrain Cdr1 and Wee1 spatially to promote Wee1 inhibition upon Cdr2 kinase activation.

Monitoring SPB biogenesis in fission yeast with high resolution and quantitative fluorescent microscopy

Like centrosomes, yeast spindle pole bodies (SPBs) undergo a tightly controlled duplication cycle in order to restrict their number to one or two per cell and promote the assembly of a bipolar spindle at mitotic entry. This conservative duplication cycle is tightly coordinated with cell cycle progression although the mechanisms that ensure this coordination remain largely unknown. In this chapter, we describe simple high resolution microscopy- and quantitative light microscopy-based methods that allow to monitor SPB biogenesis in fission yeast and may be useful to study the molecular pathways controlling the successive phases of the duplication cycle.

Cell cycle control of spindle pole body duplication and splitting by Sfi1 and Cdc31 in fission yeast

Spindle pole biogenesis and segregation are tightly coordinated to produce a bipolar mitotic spindle. In yeasts, the spindle pole body (SPB) half-bridge composed of Sfi1 and Cdc31 duplicates to promote the biogenesis of a second SPB. Sfi1 accumulates at the half-bridge in two phases in Schizosaccharomyces pombe, from anaphase to early septation and throughout G2 phase. We found that the function of Sfi1-Cdc31 in SPB duplication is accomplished before septation ends and G2 accumulation starts. Thus, Sfi1 early accumulation at mitotic exit might correspond to half-bridge duplication. We further show that Cdc31 phosphorylation on serine 15 in a Cdk1 (encoded by cdc2) consensus site is required for the dissociation of a significant pool of Sfi1 from the bridge and timely segregation of SPBs at mitotic onset. This suggests that the Cdc31 N-terminus modulates the stability of Sfi1-Cdc31 arrays in fission yeast, and impacts on the timing of establishment of spindle bipolarity.

Pom1 regulates the assembly of Cdr2-Mid1 cortical nodes for robust spatial control of cytokinesis

Pom1 regulation of Cdr2 membrane association and interaction with Mid1 prevents Cdr2 assembly into stable nodes in the cell tip region, which ensures proper positioning of cytokinetic ring precursors and accurate division plane positioning in fission yeast.

Proper division plane positioning is essential to achieve faithful DNA segregation and to control daughter cell size, positioning, or fate within tissues. In Schizosaccharomyces pombe, division plane positioning is controlled positively by export of the division plane positioning factor Mid1/anillin from the nucleus and negatively by the Pom1/DYRK (dual-specificity tyrosine-regulated kinase) gradients emanating from cell tips. Pom1 restricts to the cell middle cortical cytokinetic ring precursor nodes organized by the SAD-like kinase Cdr2 and Mid1/anillin through an unknown mechanism. In this study, we show that Pom1 modulates Cdr2 association with membranes by phosphorylation of a basic region cooperating with the lipid-binding KA-1 domain. Pom1 also inhibits Cdr2 interaction with Mid1, reducing its clustering ability, possibly by down-regulation of Cdr2 kinase activity. We propose that the dual regulation exerted by Pom1 on Cdr2 prevents Cdr2 assembly into stable nodes in the cell tip region where Pom1 concentration is high, which ensures proper positioning of cytokinetic ring precursors at the cell geometrical center and robust and accurate division plane positioning.

Fission yeast mtr1p regulates interphase microtubule cortical dwell-time

The microtubule cytoskeleton plays important roles in cell polarity, motility and division. Microtubules inherently undergo dynamic instability, stochastically switching between phases of growth and shrinkage. In cells, some microtubule-associated proteins (MAPs) and molecular motors can further modulate microtubule dynamics. We present here the fission yeast mtr1(+), a new regulator of microtubule dynamics that appears to be not a MAP or a motor. mtr1-deletion (mtr1Δ) primarily results in longer microtubule dwell-time at the cell tip cortex, suggesting that mtr1p acts directly or indirectly as a destabilizer of microtubules. mtr1p is antagonistic to mal3p, the ortholog of mammalian EB1, which stabilizes microtubules. mal3Δ results in short microtubules, but can be partially rescued by mtr1Δ, as the double mutant mal3Δ mtr1Δ exhibits longer microtubules than mal3Δ single mutant. By sequence homology, mtr1p is predicted to be a component of the ribosomal quality control complex. Intriguingly, deletion of a predicted ribosomal gene, rps1801, also resulted in longer microtubule dwell-time similar to mtr1Δ. The double-mutant mal3Δ rps1801Δ also exhibits longer microtubules than mal3Δ single mutant alone. Our study suggests a possible involvement of mtr1p and the ribosome complex in modulating microtubule dynamics.

Distinct levels in Pom1 gradients limit Cdr2 activity and localization to time and position division

Where and when cells divide are fundamental questions. In rod-shaped fission yeast cells, the DYRK-family kinase Pom1 is organized in concentration gradients from cell poles and controls cell division timing and positioning. Pom1 gradients restrict to mid-cell the SAD-like kinase Cdr2, which recruits Mid1/Anillin for medial division. Pom1 also delays mitotic commitment through Cdr2, which inhibits Wee1. Here, we describe quantitatively the distributions of cortical Pom1 and Cdr2. These reveal low profile overlap contrasting with previous whole-cell measurements and Cdr2 levels increase with cell elongation, raising the possibility that Pom1 regulates mitotic commitment by controlling Cdr2 medial levels. However, we show that distinct thresholds of Pom1 activity define the timing and positioning of division. Three conditions-a separation-of-function Pom1 allele, partial downregulation of Pom1 activity, and haploinsufficiency in diploid cells-yield cells that divide early, similar to pom1 deletion, but medially, like wild-type cells. In these cells, Cdr2 is localized correctly at mid-cell. Further, Cdr2 overexpression promotes precocious mitosis only in absence of Pom1. Thus, Pom1 inhibits Cdr2 for mitotic commitment independently of regulating its localization or cortical levels. Indeed, we show Pom1 restricts Cdr2 activity through phosphorylation of a C-terminal self-inhibitory tail. In summary, our results demonstrate that distinct levels in Pom1 gradients delineate a medial Cdr2 domain, for cell division placement, and control its activity, for mitotic commitment.

[Risk assessment of work related stress: examination and operative difficulties in sanitary field]

Work related stress can highly negatively affect not only company's productivity but also other aspects causing increased costs for absenteeism, increased number of work accident and near miss, higher turnover, reduced quality of products and services, reduced capability of renewal, and so on. In agreement with the Italian legislative decree 81/08 we evaluated stress level of workers of three different sanitary structures located in the middle of Italy. 305 workers (physicians, nurses, technicians, auxiliary nurse, white collars) were submitted to a questionnaire designed by our team of work. The sector reporting higher stress level was represented by nurses, the sector with lower stress level was made of technicians. We proposed a set of measures aiming to reduce the load of stress based on the assumption that in this sector is fundamental to develop strategies of intervention both at organizational and individual level.

[Comparison of shift work and night shifts: impacts on health and wellbeing among sanitary workers]

The generally agreed view is that there is no ideal shift system, and that most systems will have both advantages and disadvantages. As such, attention has been placed on trying to identify good and bad features of shift systems, with a view to minimising the possible ill health as a consequence of shiftwork. The present study focuses on the quality of the shift and looks at the implications for individual health and wellbeing, during the wellbeing, during the shift. Three groups of sanitary workers, one working in the morning, one working two shifts, and the other working three, took part. All completed a version of the standard shiftwork index (SSI), a set of self reported questionnaires related to health and wellbeing. The three groups differed on many outcome measures, although the differences that did exist didn't suggested advantages for one shift system over the others.

Temporal control of contractile ring assembly by Plo1 regulation of myosin II recruitment by Mid1/anillin

In eukaryotes, cytokinesis generally involves an actomyosin ring, the contraction of which promotes daughter cell segregation. Assembly of the contractile ring is tightly controlled in space and time. In the fission yeast, contractile ring components are first organized by the anillin-like protein Mid1 into medial cortical nodes. These nodes then coalesce laterally into a functional contractile ring. Although Mid1 is present at the medial cortex throughout G2, recruitment of contractile ring components to nodes starts only at mitotic onset, indicating that this event is cell-cycle regulated. Polo kinases are key temporal coordinators of mitosis and cytokinesis, and the Polo-like kinase Plo1 is known to activate Mid1 nuclear export at mitotic onset, coupling division plane specification to nuclear position. Here we provide evidence that Plo1 also triggers the recruitment of contractile ring components into medial cortical nodes. Plo1 binds at least two independent sites on Mid1, including a consensus site phosphorylated by Cdc2. Plo1 phosphorylates several residues within the first 100 amino acids of Mid1, which directly interact with the IQGAP Rng2, and influences the timing of myosin II recruitment. Plo1 thereby facilitates contractile ring assembly at mitotic onset.

Mid1p-dependent regulation of the M–G1 transcription wave in fission yeast

The control of gene expression at certain times during the mitotic cell division cycle is a common feature in eukaryotes. In fission yeast, at least five waves of gene expression have been described, with one transcribed at the M–G1 interval under the control of the PBF transcription factor complex. PBF consists of at least three transcription factors, two forkhead-like proteins Sep1p and Fkh2p, and a MADS box-like protein Mbx1p, and binds to PCB motifs found in the gene promoters. Mbx1p is under the direct control of the polo-like kinase Plo1p and the Cdc14p-like phosphatase Clp1p (Flp1p). Here, we show that M–G1 gene expression in fission yeast is also regulated by the anillin-like protein, Mid1p (Dmf1p). Mid1p binds in vivo to both Fkh2p and Sep1p, and to the promoter regions of M–G1 transcribed genes. Mid1p promoter binding is dependent on Fkh2p, Plo1p and Clp1p. The absence of mid1+ in cells results in partial loss of M–G1 specific gene expression, suggesting that it has a negative role in controlling gene expression. This phenotype is exacerbated by also removing clp1+, suggesting that Mid1p and Clp1p have overlapping functions in controlling transcription. As mid1+ is itself expressed at M–G1, these observations offer a new mechanism whereby Mid1p contributes to controlling cell cycle-specific gene expression as part of a feedback loop.

Mechanisms controlling division-plane positioning

A critical and irreversible step in the cell division cycle is cytokinesis which physically separates the two daughter cells. This event is consequently subject to tight spatial and temporal regulation. This review focuses on the spatial regulatory mechanisms controlling the position of the division plane. Studies performed in prokaryotic and eukaryotic systems have revealed that various signal-emitting spatial cues - mitotic spindle, nucleus, nucleoid or cell tips - can favour or inhibit the assembly of the cytokinetic apparatus in their vicinity. Most often, several mechanisms operate in parallel to integrate spatial information and promote faithful genome segregation as well as proper cytoplasmic division. We primarily describe the spatial regulatory mechanisms operating in the fission yeast model system, where a detailed molecular understanding of cytokinesis has been achieved. In this system, spatial regulations target a major factor controlling the position of the division plane, the anillin-like protein Mid1. These mechanisms are then compared to spatial regulatory mechanisms prevailing in animal cells and rod-shaped bacteria.

Effects of palladium nanoparticles on the cytokine release from peripheral blood mononuclear cells of non-atopic women

The object of this study is to determine the cytokine release from PBMCs exposed to Pd model nanoparticles emitted from catalytic converters. PBMCs of 8 healthy non-atopic women were incubated in the presence of Pd nanoparticles (5-10 nm) or salt (potassium hexa-chloropalladate) 10-5 and 10-6 M. Release of cytokines in supernatant of PBMCs was then determined. In cultures without LPS, IL-10 and IL-17 release from PBMCs was inhibited by Pd salt, while Pd nanoparticles inhibited TNF-alpha and IL-17 release. In LPS-stimulated cultures, release of IFN-gamma, TNF-alpha, IL-10 and IL-17 was inhibited by Pd salt, whereas IFN-gamma release was enhanced and TNF-alpha and IL-17 release was inhibited by Pd nanoparticles. In conclusion, Pd salt inhibits cytokine release, whereas Pd nanoparticles exert modulatory effects enhancing the release of IFN-gamma, a Th1 cytokine typical of delayed allergic reactions. This result is interesting considering the increase of allergic contact dermatitis to Pd in people exposed to Pd nanoparticles in urban environments.

Spatial control of cytokinesis by Cdr2 kinase and Mid1/anillin nuclear export

Maintaining genome integrity and cellular function requires proper positioning of the cell division plane. In most eukaryotes, cytokinesis relies on a contractile actomyosin ring positioned by intrinsic spatial signals that are poorly defined at the molecular level. Fission yeast cells assemble a medial contractile ring in response to positive spatial cues from the nucleus at the cell center and negative spatial cues from the cell tips. These signals control the localization of the anillin-like protein Mid1, which defines the position of the division plane at the medial cortex, where it recruits contractile-ring components at mitosis onset. Here we show that Cdr2 kinase anchors Mid1 at the medial cortex during interphase through association with the Mid1 N terminus. This association underlies the negative regulation of Mid1 distribution by cell tips. We also demonstrate that the positive signaling from the nucleus is based on Mid1 nuclear export, which links division-plane position to nuclear position during early mitosis. After nuclear displacement, Mid1 nuclear export is dominant over Cdr2-dependent positioning of Mid1. We conclude that Cdr2- and nuclear export-dependent positioning of Mid1 constitute two overlapping mechanisms that relay cell polarity and nuclear positional information to ensure proper division-plane specification.

Physical mechanisms redirecting cell polarity and cell shape in fission yeast

The cylindrical rod shape of the fission yeast Schizosaccharomyces pombe is organized and maintained by interactions between the microtubule, cell membrane, and actin cytoskeleton [1]. Mutations affecting any components in this pathway lead to bent, branched, or round cells [2]. In this context, the cytoskeleton controls cell polarity and thus dictates cell shape. Here, we use soft-lithography techniques to construct microfluidic channels to control cell shape. We show that when wild-type rod-shaped cells are physically forced to grow in a bent fashion, they will reorganize their cytoskeleton and redirect cell polarity to make new ectopic cell tips. Moreover, when bent or round mutant cells are physically forced to conform to the wild-type rod-shape, they will reverse their mutational phenotypes by reorganizing their cytoskeleton to maintain proper wild-type-like localization of microtubules, cell-membrane proteins, and actin. Our study provides direct evidence that the cytoskeleton controls cell polarity and cell shape and demonstrates that cell shape also controls the organization of the cytoskeleton in a feedback loop. We present a model of the feedback loop to explain how fission yeast maintain a rod shape and how perturbation of specific parameters of the loop can lead to different cell shapes.

[Professional exposure to natural ultraviolet radiation: risk assessment and management and preventing strategies]

The aim of our study was to verify the impact of work risk factor in causing cutaneous neoplasia on a group of patients and to assess the risk of exposure to UV on outdoor workers. The survey was divided in three phases: a) Questionnaire, b) Dermatological clinical examination. c) Exposure measurement by spectral radiance method (mW/cm2). 248 subjects were enrolled, 100 of which affected by basal cellular carcinoma (BCC) (68% M and 32% F: mean age 70 +/- 11.93 y) 130 by melanoma (42% M and 58% F; mean age 53 +/- 17.35 y) and 18 by squamous cellular carcinoma (33% F and 67% M: mean age 78 +/- 11.41 y). In addiction 22 healthy male subjects exposed to UV were examined (mean age 38.59 +/- 13.65 y; specific working age 11.88 +/- 10.92 y). The assessment of UV exposure was performed over a 24 days timeframe during summer 2007, all over the working day. Furthermore, maximum allowed exposure time (t(max)) without protection was calculated according to ACGIH guidelines in order to prevent cutaneous alterations. It turned out that the UV exposure, both in working and spare time, is the root cause for squamous cellular cancer developing. Furthermore our results proved that also BCC is related to the overall UV exposure. No clear link to the UV exposure was found for cutaneous melanoma. No precancerous lesions were observed on shortly exposed subjects. The measurements performed revealed, as expected, lower exposure during first and last hours of the day without any particular constrain on t(max), and maximum exposure in the timeframe between 10:00 AM and 4:00 PM. Therefore, it is necessary to pay higher attention to the UV exposure and related consequences on employees health in order to provide with the most suitable preventing measures such the usage of protections depending from the requested exposure time.

[Occupational risk stress in shift workers]

Aim of our study was to assess the stress risk at work in a group of nurses. 197 workers (nurses, auxiliary, physiotherapists, midwives and technicians of laboratory) were enrolled divided in two sets respectively of 100 people (subset A) with daily and nightly shifts and 97 (subset B) only daily workers. The mean age was 43.29 years (DS +/- 8.13) in subset A and 46.85 years (DS +/- 7.48) in subset B. For the survey S-90, a questionnaire composed by 90 items faces to frame some of the possible factors of risk has been used and the relative effects on health's state induced by the occupational stress were analyzed. The results show a possible greater risk of daily sleepiness in workers with nightly job. The majority of hypertension workers in subgroup B could depend more on the elevated mean age of this sample. Although a greater perception of the psychological load has been found, statistically meaningful association between the insurgence of gastrointestinal symptoms and shift was not showed.

[Cervical, thoracic and upper limb load assessment in dental professionals]

In order to analyze the effect of working posture on the level of neck, back and shoulder muscular activity, a clinico-anamnestic, electromyographic and postural study of 34 dentistry was undertaken. Using surface electrodes, the level of muscular activity was recorded. The results showed that neck flexed working posture is prevalent: using stereomicroscope gave lower levels than with or without enlarging systems, such as glasses.

[Risk assessment in upper limb overload]

One of the most important factors of the work-related musculoskeletal disorders of the upper extremities (WMSDs) is the biomechanical overload. The purpose of this study is to evaluate the possibility to predict the upper limb repetitive stress, according to risk assessment procedures. In order to this aim, we gathered clinical-anamnestic data and risk assessment considerations of a cohort of workers in a car industry.

Pom1 kinase links division plane position to cell polarity by regulating Mid1p cortical distribution

In fission yeast, Mid1p, a major determinant for division plane position, defines a medial cortical compartment where it recruits myosin II at the onset of mitosis to initiate contractile ring assembly. How Mid1p is restricted to the medial cortex is unknown. We report here that in a pom1 polarity mutant, which displays a monopolar growth pattern, Mid1p distribution expands towards the non-growing cell tip, uncoupling Mid1p localization from nuclear position. This accounts for the displacement of the contractile ring during mitosis. By contrast, Mid1p localization is normal in a bud6Δ strain, indicating that Mid1p misdistribution is not a general consequence of monopolar growth. We conclude that Pom1 kinase acts as a negative regulator of Mid1p distribution, excluding Mid1p from non-growing ends, whereas a Pom1-independent mechanism prevents Mid1p association with growing ends. Our work therefore provides evidence that cell polarity regulators influence the distribution of Mid1p, linking division plane position to cell polarity.

[The diagnosis of occupational diseases: a specific task of occupational doctors]

The Authors examine the problem dealing with Occupational disease diagnosis focusing five main points: diseases of probable/possible occupational origin; chronic and acute diseases; diseases due to biological agents; presumptive causation in legal compensation; public health statistics and medical reports. They conclude that new rules are needed and more advice from Occupational Medicine is required.

[Breathing sleep disturbances and occupational medicine: study of 20 clinical cases]

During 2004, in the Center for Sleep Disorders, a questionnaire including Epworth sleepiness scale (ES) was administered to 120 subjects; 20 male subjects of this group with elevated score (ES >14) were selected and submitted to polysomnography. Subjects, all in working age, were represented by 3 (15%) shift-workers, 9 (45%) drivers, 17 (85%) industrial workers (among those 5 building workers) and 3 (15%) employers. By polysomnography, moderatelsevere OSAHS was diagnosed in all subjects (40% moderate, 60% severe). CPAP (Continuous Positive Airway Pressure) therapy led to an improvement of clinical symptoms since the first month. Counselling of Occupational Medicine Physician with the Center for Sleep Disorders, was useful to direct the action of Competent Doctor, especially for jobs requiring high vigilance (drivers or shift-worker). The pass certificate for jobs with an high risk (alone, in high places, heavy means drivers) cannot avoid to evaluate this pathology, that is often associated to other related risk factors (obesity, hypertension, diabetes), because it compromises both the specific suitability and the protection of common health and safety.

Efficient formation of bipolar microtubule bundles requires microtubule-bound gamma-tubulin complexes

The mechanism for forming linear microtubule (MT) arrays in cells such as neurons, polarized epithelial cells, and myotubes is not well understood. A simpler bipolar linear array is the fission yeast interphase MT bundle, which in its basic form contains two MTs that are bundled at their minus ends. Here, we characterize mto2p as a novel fission yeast protein required for MT nucleation from noncentrosomal γ-tubulin complexes (γ-TuCs). In interphase mto2Δ cells, MT nucleation was strongly inhibited, and MT bundling occurred infrequently and only when two MTs met by chance in the cytoplasm. In wild-type 2, we observed MT nucleation from γ-TuCs bound along the length of existing MTs. We propose a model on how these nucleation events can more efficiently drive the formation of bipolar MT bundles in interphase. Key to the model is our observation of selective antiparallel binding of MTs, which can both explain the generation and spatial separation of multiple bipolar bundles.

[Evaluation of risks of biomechanical overload of the upper limb in physical kinesis therapists]

Physical therapists are at risk for work-related musculoskeletal disorders (WMSDs). Contributing risk factors are job-task, mental stress and biomechanical overload, due to fixed and incorrect postures of neck, upper limbs and back. The purpose of this study was to investigate, by questionnaire and the use of muscle superficial EMG recording and analysis, the workload in the physical therapist activity, in order to provide suitable preventive measures.

[Longitudinal study of a population exposed to risk of biomechanical overload of the upper limb]

One of the most important factors of the work-related musculoskeletal disorders of the upper extremities (WMSDs) is the biomechanical overload. The purpose of this study is to evaluate the possibility of the worker fitting to the job, to decrease the upper limb repetitive stress. In order to this aim, we have collected and compared, in different controls at the distance of two years, the clinical-anamnestic and instrumental data of a cohort of workers in a car industry.

Ase1p organizes antiparallel microtubule arrays during interphase and mitosis in fission yeast

Proper microtubule organization is essential for cellular processes such as organelle positioning during interphase and spindle formation during mitosis. The fission yeast Schizosaccharomyces pombe presents a good model for understanding microtubule organization. We identify fission yeast ase1p, a member of the conserved ASE1/PRC1/MAP65 family of microtubule bundling proteins, which functions in organizing the spindle midzone during mitosis. Using fluorescence live cell imaging, we show that ase1p localizes to sites of microtubule overlaps associated with microtubule organizing centers at both interphase and mitosis. ase1Delta mutants fail to form overlapping antiparallel microtubule bundles, leading to interphase nuclear positioning defects, and premature mitotic spindle collapse. FRAP analysis revealed that interphase ase1p at overlapping microtubule minus ends is highly dynamic. In contrast, mitotic ase1p at microtubule plus ends at the spindle midzone is more stable. We propose that ase1p functions to organize microtubules into overlapping antiparallel bundles both in interphase and mitosis and that ase1p may be differentially regulated through the cell cycle.

Imaging green fluorescent protein fusions in living fission yeast cells

The use of green fluorescent protein (GFP) fusions as biosensors for examining protein localization and dynamics has revolutionized cell biology. Here, we describe the methods developed for imaging of GFP-fusions in the fission yeast Schizosaccharomyces pombe using fluorescence microscopy, with a focus on the use of time-lapse imaging to analyze the dynamics of microtubules. We discuss the considerations in fluorescence microscopy, cell preparation, data acquisition, and image analysis appropriate for analysis of living cells.

Performance indicators for the efficiency analysis of urban drainage systems

Performance indicators implemented in a decision support system (DSS) for the technical, managerial and economic evaluation of urban drainage systems (UDS), called MOMA FD, are presented. Several kinds of information are collected and processed by MOMA FD to evaluate both present situation and future scenarios of development and enhancement. Particular interest is focused on the evaluation of the environmental impact, which is considered a very relevant factor in the decision making process to identify the priorities for UDS improvements.

C-terminal anchoring of mid1p to membranes stabilizes cytokinetic ring position in early mitosis in fission yeast

mid1p is a key factor for the central positioning of the cytokinetic ring in Schizosaccharomyces pombe. In interphase and early mitosis, mid1p forms a medial cortical band overlying the nucleus, which may represent a landmark for cytokinetic ring assembly. It compacts before anaphase into a tight ring with other cytokinetic ring components. We show here that mid1p binds to the medial cortex by at least two independent means. First, mid1p C-terminus association with the cortex requires a putative amphipathic helix adjacent to mid1p nuclear localization sequence (NLS), which is predicted to insert directly into the lipid bilayer. This association is stabilized by the polybasic NLS. mid1p mutated within the helix and the NLS forms abnormal filaments in early mitosis that are not properly anchored to the medial cortex. Misplaced rings assemble in late mitosis, indicating that mid1p C-terminus binding to membranes stabilizes cytokinetic ring position. Second, the N terminus of mid1p has the ability to associate faintly with the medial cortex and is sufficient to form tight rings. In addition, we show that mid1p oligomerizes. We propose that membrane-bound oligomers of mid1p assemble recruitment "platforms" for cytokinetic ring components at the medial cortex and stabilize the ring position during its compaction.

Development and application of CVD diamond detectors to 14 MeV neutron flux monitoring

CVD diamond is an interesting material for radiation detection, its atomic number (Z = 6) is close to that of soft tissues (Z = 7.1) and it can also work in harsh environments. Since many years CVD diamond films have been grown at the Faculty of Engineering, Rome 'Tor Vergata' University, and in 1998 a collaboration with ENEA Fusion Division was established to develop fast neutron monitors to be used in fusion tokamak environment. In this paper the first test of a 120 microm thick polycrystalline CVD diamond detector used for monitoring 14.7 MeV neutrons emission produced with the Frascati Neutron Generator (FNG) is reported. The detector operates in air and in pulse mode. The time irradiation profiles recorded with the CVD diamond detector were compared with those recorded by the standard monitors available at FNG (SSD, fission chamber, NE-213). Good stability and capability to operate in neutron flux up to 1.5 x 10(8) n cm(-2) s(-1) was observed. The radiation hardness property was also investigated using a 460 microm thick film and these results are also reported.

Fission yeast cdc31p is a component of the half-bridge and controls SPB duplication

The fission yeast spindle pole body (SPB) is a nucleus-associated organelle that duplicates once each cell cycle during interphase. Duplicated SPBs serve as the poles of an intranuclear mitotic spindle after their insertion into the nuclear envelope in mitosis (Ding et al., Mol. Biol. Cell 8, 1461-1479). Here, we report the identification and characterization of Schizosaccharomyces pombe cdc31p, a member of the conserved calcium-binding centrin/CDC31 family. Immunofluorescence and immunoelectron microscopy show that cdc31p is a SPB component localized at the half-bridge structure of the SPB. cdc31 is an essential gene and Deltacdc31 cells and cdc31 conditional mutant cells arrest in mitosis with a monopolar mitotic spindle organized from a single SPB. EM analysis demonstrates that mutant cdc31 cells fail to duplicate the SPB. In addition, cdc31p exhibits genetic interactions with the SPB component sad1p and is required for sad1p localization. Finally, cdc31 mutant can undergo single or multiple rounds of septation before the exit from mitosis, suggesting that cdc31p activity or SPB duplication may be required for the proper coordination between the exit from mitosis and the initiation of septation.

Mid2p stabilizes septin rings during cytokinesis in fission yeast

Septins are filament-forming proteins with a conserved role in cytokinesis. In the fission yeast Schizosaccharomyces pombe, septin rings appear to be involved primarily in cell-cell separation, a late stage in cytokinesis. Here, we identified a protein Mid2p on the basis of its sequence similarity to S. pombe Mid1p, Saccharomyces cerevisiae Bud4p, and Candida albicans Int1p. Like septin mutants, mid2delta mutants had delays in cell-cell separation. mid2delta mutants were defective in septin organization but not contractile ring closure or septum formation. In wild-type cells, septins assembled first during mitosis in a single ring and during septation developed into double rings that did not contract. In mid2delta cells, septins initially assembled in a single ring but during septation appeared in the cleavage furrow, forming a washer or disc structure. FRAP studies showed that septins are stable in wild-type cells but exchange 30-fold more rapidly in mid2delta cells. Mid2p colocalized with septins and required septins for its localization. A COOH-terminal pleckstrin homology domain of Mid2p was required for its localization and function. No genetic interactions were found between mid2 and the related gene mid1. Thus, these studies identify a new factor responsible for the proper stability and function of septins during cytokinesis.

Kar9 asymmetrical loading on spindle poles mediates proper spindle alignment in budding yeast

In the February 21 issue of Cell, demonstrate that asymmetrical loading of Kar9 onto astral microtubules (MTs) emanating from the bud-ward-directed spindle pole ensures delivery of this spindle pole to the bud. Kar9 mediates alignment of the spindle with the cell polarity axis through a Myo2-dependent mechanism that reorients astral MTs toward the bud.