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Centrioles are the core constituent of centrosomes, microtubule-organizing centers involved in directing mitotic spindle assembly and chromosome segregation in animal cells. In sexually reproducing species, centrioles degenerate during oogenesis and female meiosis is usually acentrosomal. Centrioles are retained during male meiosis and, in most species, are reintroduced with the sperm during fertilization, restoring centriole numbers in embryos. In contrast, the presence, origin, and function of centrioles in parthenogenetic species is unknown. We found that centrioles are maternally inherited in two species of asexual parthenogenetic nematodes and identified two different strategies for maternal inheritance evolved in the two species. In Rhabditophanes diutinus, centrioles organize the poles of the meiotic spindle and are inherited by both the polar body and embryo. In Disploscapter pachys, the two pairs of centrioles remain close together and are inherited by the embryo only. Our results suggest that maternally-inherited centrioles organize the embryonic spindle poles and act as a symmetry-breaking cue to induce embryo polarization. Thus, in these parthenogenetic nematodes, centrioles are maternally-inherited and functionally replace their sperm-inherited counterparts in sexually reproducing species. Centrioles are broken down during oogenesis and are provided by the sperm during sexual reproduction, though how centriole numbers are regulated during asexual reproduction is unclear. Here they study two asexually reproducing nematodes and identify distinct mechanisms for maternal centrosome inheritance. [ABSTRACT FROM AUTHOR]

During cell division, chromosome congression to the spindle center, their orientation along the spindle long axis and alignment at the metaphase plate depend on interactions between spindle microtubules and kinetochores, and are pre-requisite for chromosome bi-orientation and accurate segregation. How these successive phases are controlled during oocyte meiosis remains elusive. Here we provide 4D live imaging during the first meiotic division in C. elegans oocytes with wild-type or disrupted kinetochore protein function. We show that, unlike in monocentric organisms, holocentric chromosome bi-orientation is not strictly required for accurate chromosome segregation. Instead, we propose a model in which initial kinetochore-localized BHC module (comprised of BUB-1Bub1, HCP-1/2CENP-F and CLS-2CLASP)-dependent pushing acts redundantly with Ndc80 complex-mediated pulling for accurate chromosome segregation in meiosis. In absence of both mechanisms, homologous chromosomes tend to co-segregate in anaphase, especially when initially mis-oriented. Our results highlight how different kinetochore components cooperate to promote accurate holocentric chromosome segregation in oocytes of C. elegans. The exact function of kinetochore proteins in meiosis remains unclear. Using live imaging of C. elegans oocytes, the authors systematically study the contribution of each kinetochore sub-complex and describe a push-pull mechanism that confers robustness to chromosome segregation. [ABSTRACT FROM AUTHOR]

The optic radiations (OR) are white matter tracts forming the posterior part of the visual ways. As an important inter-individual variability exists, atlases may be inefficient to locate the OR in a given subject. We designed a fully automatic method to delimitate the OR on a magnetic resonance imaging using tractography. On 15 healthy subjects, we evaluated the validity of our method by comparing the outputs to the Jülich post-mortem histological atlas, and its reproducibility. We also evaluated its feasibility on 98 multiple sclerosis (MS) patients. We correlated different visual outcomes with the inflammatory lesions volume within the OR reconstructed with different methods (our method, atlas, TractSeg). Our method reconstructed the OR bundle in all healthy subjects (< 2 h for most of them), and was reproducible. It demonstrated good classification indexes: sensitivity up to 0.996, specificity up to 0.993, Dice coefficient up to 0.842, and an area under the receiver operating characteristic (ROC) curve of 0.981. Our method reconstructed the OR in 91 of the 98 MS patients (92.9%, < 6 h for most of patients). Compared to an atlas-based approach and the TractSeg method, the inflammatory lesions volume in the OR measured with our method better correlated with the visual cortex volume, visual acuity and mean peripapillar retinal nerve fiber layer thickness. Our method seems to be efficient to reconstruct the OR in healthy subjects, and seems applicable to MS patients. It may be more relevant than an atlas based approach. [ABSTRACT FROM AUTHOR]

During cell division, spindle microtubules ensure an equal repartition of chromosomes between the two daughter cells. While the kinetochore-dependent mechanisms that drive mitotic chromosome segregation are well understood, in oocytes of most species atypical spindles assembled in absence of centrosomes entail poorly understood mechanisms of chromosome segregation. In particular, the structure(s) responsible for force generation during meiotic chromosome separation in oocytes is unclear. Using quantitative light microscopy, electron tomography, laser-mediated ablation, and genetic perturbations in the Caenorhabditis elegans oocyte, we studied the mechanism of chromosome segregation in meiosis. We find spindle poles are largely dispensable, and in fact act as brakes for chromosome segregation. Instead, our results suggest that CLS-2-dependent microtubules of the meiotic central spindle, located between the segregating chromosomes and aligned along the axis of segregation, are essential. Our results support a model in which inter-chromosomal microtubules of the central spindle push chromosomes apart during meiotic anaphase in oocytes. [ABSTRACT FROM AUTHOR]

Objectives: To determine the diagnostic accuracy of pharmacokinetic parameters measured by dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) in predicting the response of brain metastases to antineoplastic therapy in patients with lung cancer.Methods: Forty-four consecutive patients with lung cancer, harbouring 123 newly diagnosed brain metastases prospectively underwent conventional 3-T MRI at baseline (within 1 month before treatment), during the early (7-10 weeks) and midterm (5-7 months) post-treatment period. An additional DCE MRI sequence was performed during baseline and early post-treatment MRI to evaluate baseline pharmacokinetic parameters (K trans, k ep, v e, v p) and their early variation (∆K trans, ∆k ep, ∆v e, ∆v p). The objective response was judged by the volume variation of each metastasis from baseline to midterm MRI. ROC curve analysis determined the best DCE MRI parameter to predict the objective response.Results: Baseline DCE MRI parameters were not associated with the objective response. Early ∆K trans, ∆v e and ∆v p were significantly associated with the objective response (p = 0.02, p = 0.001 and p = 0.02, respectively). The best predictor of objective response was ∆v e with an area under the curve of 0.93 [95% CI = 0.87, 0.99].Conclusions: DCE MRI and early ∆v e may be a useful tool to predict the objective response of brain metastases in patients with lung cancer.Key Points: • DCE MRI could predict the response of brain metastases from lung cancer • ∆v e was the best predictor of response • DCE MRI could be used to individualize patients' follow-up. [ABSTRACT FROM AUTHOR]

A critical structure poised to coordinate chromosome segregation with division plane specification is the central spindle that forms between separating chromosomes after anaphase onset. The central spindle acts as a signalling centre that concentrates proteins essential for division plane specification and contractile ring constriction. However, the molecular mechanisms that control the initial stages of central spindle assembly remain elusive. Using Caenorhabditis elegans zygotes, we found that the microtubule-bundling protein SPD-1PRC1 and the motor ZEN-4MKLP-1 are required for proper central spindle structure during its elongation. In contrast, we found that the kinetochore controls the initiation of central spindle assembly. Specifically, central spindle microtubule assembly is dependent on kinetochore recruitment of the scaffold protein KNL-1, as well as downstream partners BUB-1, HCP-1/2CENP-F and CLS-2CLASP; and is negatively regulated by kinetochore-associated protein phosphatase 1 activity. This in turn promotes central spindle localization of CLS-2CLASP and initial central spindle microtubule assembly through its microtubule polymerase activity. Together, our results reveal an unexpected role for a conserved kinetochore protein network in coupling two critical events of cell division: chromosome segregation and cytokinesis. [ABSTRACT FROM AUTHOR]

We consider wireless networks that can be modeled by multiple access channels in which all the terminals are equipped with multiple antennas. The propagation model used to account for the effects of transmit and receive antenna correlations is the unitary-invariant-unitary model, which is one of the most general models available in the literature. In this context, we introduce and analyze two resource allocation games. In both games, the mobile stations selfishly choose their power allocation policies in order to maximize their individual uplink transmission rates; in particular they can ignore some specified centralized policies. In the first game considered, the base station implements successive interference cancellation (SIC) and each mobile station chooses his best space-time power allocation scheme; here, a coordination mechanism is used to indicate to the users the order in which the receiver applies SIC. In the second framework, the base station is assumed to implement single-user decoding. For these two games a thorough analysis of the Nash equilibrium is provided: the existence and uniqueness issues are addressed; the corresponding power allocation policies are determined by exploiting random matrix theory; the sum-rate efficiency of the equilibrium is studied analytically in the low and high signal-to-noise ratio regimes and by simulations in more typical scenarios. Simulations show that, in particular, the sum-rate efficiency is high for the type of systems investigated and the performance loss due to the use of the proposed suboptimum coordination mechanism is very small. [ABSTRACT FROM AUTHOR]

Although assembly of acentrosomal meiotic spindles has been extensively studied, little is known about the segregation of chromosomes on these spindles. Here, we show in Caenorhabditis elegans oocytes that the kinetochore protein, KNL-1, directs assembly of meiotic kinetochores that orient chromosomes. However, in contrast to mitosis, chromosome separation during meiotic anaphase is kinetochore-independent. Before anaphase, meiotic kinetochores and spindle poles disassemble along with the microtubules on the poleward side of chromosomes. During anaphase, microtubules then form between the separating chromosomes. Functional analysis implicated a set of proteins that localize to a ring-shaped domain between kinetochores during pre-anaphase spindle assembly and anaphase separation. These proteins are localized by the chromosomal passenger complex, which regulates the loss of meiotic chromosome cohesion. Thus, meiotic segregation in C. elegans is a two-stage process, where kinetochores orient chromosomes, but are then dispensable for their separation. We suggest that separation is controlled by a meiosis-specific chromosomal domain to coordinate cohesin removal and chromosome segregation. [ABSTRACT FROM AUTHOR]

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A correction to the article "Kinetochore components are required for central spindle assembly" in the April 13, 2015 issue is presented.