A force-sensitive mutation reveals a non-canonical role for dynein in anaphase progression.

The diverse roles of the dynein motor in shaping microtubule networks and cargo transport complicate in vivo analysis of its functions significantly. To address this issue, we have generated a series of missense mutations in Drosophila Dynein heavy chain. We show that mutations associated with human neurological disease cause a range of defects, including impaired cargo trafficking in neurons.

Imaging and Analysis of Drosophila Neural Stem Cell Asymmetric Division.

Cell division is a conserved process among eukaryotes. It is designed to segregate chromosomes into future daughter cells and involves a complex rearrangement of the cytoskeleton, including microtubules and actin filaments. An additional level of complexity is present in asymmetric dividing stem cells because cytoskeleton elements are also regulated by polarity cues.

A force-sensitive mutation reveals a spindle assembly checkpoint-independent role for dynein in anaphase progression.

The cytoplasmic dynein-1 (dynein) motor organizes cells by shaping microtubule networks and moving a large variety of cargoes along them. However, dynein's diverse roles complicate studies of its functions significantly. To address this issue, we have used gene editing to generate a series of missense mutations in Dynein heavy chain (Dhc).

The histone methyltransferase NSD3 contributes to sister chromatid cohesion and to cohesin loading at mitotic exit.

Sister chromatid cohesion is a multi-step process implemented throughout the cell cycle to ensure the correct transmission of chromosomes to daughter cells. Although cohesion establishment and mitotic cohesion dissolution have been extensively explored, the regulation of cohesin loading is still poorly understood. Here, we report that the methyltransferase NSD3 is essential for mitotic sister chromatid cohesion before mitosis entry.

Live imaging of Drosophila melanogaster neural stem cells with photo-ablated centrosomes.

Drosophila neural stem cells (NSCs) divide asymmetrically to generate siblings of different sizes. This model system has proved helpful in deciphering the contribution of polarity cues and the mitotic spindle in asymmetric cell division. Here, we describe a technique we developed to flatten cultured Drosophila brain explants to accurately image the cytoskeleton in live NCSs.

Annexin A2 and Ahnak control cortical NuMA-dynein localization and mitotic spindle orientation.

Proper mitotic spindle orientation depends on the correct anchorage of astral microtubules to the cortex. It relies on the remodeling of the cell cortex, a process not fully understood. Annexin A2 (Anx2; also known as ANXA2) is a protein known to be involved in cortical domain remodeling.

Peripheral astral microtubules ensure asymmetric furrow positioning in neural stem cells.

Neuroblast division is characterized by asymmetric positioning of the cleavage furrow, resulting in a large difference in size between the future daughter cells. In animal cells, furrow placement and assembly are governed by centralspindlin that accumulates at the equatorial cell cortex of the future cleavage site and at the spindle midzone. In neuroblasts, these two centralspindlin populations are spatially and temporally separated.

Drosophila Tubulin-Specific Chaperone E Recruits Tubulin around Chromatin to Promote Mitotic Spindle Assembly.

Proper assembly of mitotic spindles requires microtubule nucleation not only at the centrosomes but also around chromatin. In this study, we found that the Drosophila tubulin-specific chaperone dTBCE is required for the enrichment of tubulin in the nuclear space after nuclear envelope breakdown and for subsequent promotion of spindle microtubule nucleation. These events depend on the CAP-Gly motif found in dTBCE and are regulated by Ran and lamin proteins.

Dual control of Kinesin-1 recruitment to microtubules by Ensconsin in neuroblasts and oocytes.

Ensconsin (also known as MAP7) controls spindle length, centrosome separation in brain neuroblasts (NBs) and asymmetric transport in oocytes. The control of spindle length by Ensconsin is Kinesin-1 independent but centrosome separation and oocyte transport require targeting of Kinesin-1 to microtubules by Ensconsin. However, the molecular mechanism used for this targeting remains unclear.

Aurora A Protein Kinase: To the Centrosome and Beyond.

Accurate chromosome segregation requires the perfect spatiotemporal rearrangement of the cellular cytoskeleton. Isolated more than two decades ago from , Aurora A is a widespread protein kinase that plays key roles during cell division. Numerous studies have described the localisation of Aurora A at centrosomes, the mitotic spindle, and, more recently, at mitotic centromeres.

[Nursing homes and fall in the consumption of psychotropic medications].

The consumption of psychotropic drugs in elderly people remains a concern in France, including in nursing homes. A comparative analysis of prescriptions for psychotropic medication in nursing homes in 2013 and 2015 based on the computer system of the French national health insurance scheme shows a significant reduction in the prescribing of these medications. Example of a nursing home in Dijon.

14-3-3 regulation of Ncd reveals a new mechanism for targeting proteins to the spindle in oocytes.

The meiotic spindle is formed without centrosomes in a large volume of oocytes. Local activation of crucial spindle proteins around chromosomes is important for formation and maintenance of a bipolar spindle in oocytes. We found that phosphodocking 14-3-3 proteins stabilize spindle bipolarity in oocytes.

Drosophila Aurora A regulates mitotic timing in cancer stem cells: Possible therapeutic implications.

Loss of Aurora A in Drosophila neuroblasts promotes loss of cell fate, leading to brain tumors. We showed that these tumor stem cells are delayed during mitosis and efficiently segregate their chromosomes even without the spindle assembly checkpoint. Here, we discuss the possible relevance of our results to human cancers.

Spindle assembly checkpoint inactivation fails to suppress neuroblast tumour formation in aurA mutant Drosophila.

Tissue homeostasis requires accurate control of cell proliferation, differentiation and chromosome segregation. Drosophila sas-4 and aurA mutants present brain tumours with extra neuroblasts (NBs), defective mitotic spindle assembly and delayed mitosis due to activation of the spindle assembly checkpoint (SAC). Here we inactivate the SAC in aurA and sas-4 mutants to determine whether the generation of aneuploidy compromises NB proliferation.

Homozygous STIL mutation causes holoprosencephaly and microcephaly in two siblings.

Holoprosencephaly (HPE) is a frequent congenital malformation of the brain characterized by impaired forebrain cleavage and midline facial anomalies. Heterozygous mutations in 14 genes have been identified in HPE patients that account for only 30% of HPE cases, suggesting the existence of other HPE genes. Data from homozygosity mapping and whole-exome sequencing in a consanguineous Turkish family were combined to identify a homozygous missense mutation (c.

Ensconsin/Map7 promotes microtubule growth and centrosome separation in Drosophila neural stem cells.

The mitotic spindle is crucial to achieve segregation of sister chromatids. To identify new mitotic spindle assembly regulators, we isolated 855 microtubule-associated proteins (MAPs) from Drosophila melanogaster mitotic or interphasic embryos. Using RNAi, we screened 96 poorly characterized genes in the Drosophila central nervous system to establish their possible role during spindle assembly.

CDK11(p58) kinase activity is required to protect sister chromatid cohesion at centromeres in mitosis.

The cyclin-dependent kinase CDK11(p58) is specifically expressed at G2/M phase. CDK11(p58) depletion leads to different cell cycle defects such as mitotic arrest, failure in centriole duplication and centrosome maturation, and premature sister chromatid separation. We report that upon CDK11 depletion, loss of sister chromatid cohesion occurs during mitosis but not during G2 phase.

MNK1 kinase activity is required for abscission.

MNK1 is a serine/threonine kinase identified as a target for MAP kinase pathways. Using chemical drug, kinase-dead expression or knockdown by RNA interference, we show that inhibition of MNK1 induces the formation of multinucleated cells, which can be rescued by expressing a form of MNK1 that is resistant to RNA interference. We found that the active human form of MNK1 localises to centrosomes, spindle microtubules and the midbody.

CDK11(p58) is required for centriole duplication and Plk4 recruitment to mitotic centrosomes.

Background: CDK11(p58) is a mitotic protein kinase, which has been shown to be required for different mitotic events such as centrosome maturation, chromatid cohesion and cytokinesis.

Methodology/principal Findings: In addition to these previously described roles, our study shows that CDK11(p58) inhibition induces a failure in the centriole duplication process in different human cell lines. We propose that this effect is mediated by the defective centrosomal recruitment of proteins at the onset of mitosis.

Aurora A contributes to p150(glued) phosphorylation and function during mitosis.

Aurora A is a spindle pole-associated protein kinase required for mitotic spindle assembly and chromosome segregation. In this study, we show that Drosophila melanogaster aurora A phosphorylates the dynactin subunit p150(glued) on sites required for its association with the mitotic spindle. Dynactin strongly accumulates on microtubules during prophase but disappears as soon as the nuclear envelope breaks down, suggesting that its spindle localization is tightly regulated.

[Centrosomes, mitotic spindle and cancer: find the odd one out!].

Centrosomes are essential protagonists during cell division through microtubule nucleation and spindle formation which are key to the harmonious distribution of sister chromatids in the two daughter cells. However, during the past decade, a wealth of new observations has extended their role beyond mitosis, particularly in the asymmetrical partition of cell fate determinants. Remarkably, asymmetric centrosome inheritance per se, through the segregation of differently aged mother -centrioles, seems to regulate the differential behaviour of daughter cells, in part through asynchronous expression of primary cilia, governing the response to environmental signals.

Human PRP4 kinase is required for stable tri-snRNP association during spliceosomal B complex formation.

Reversible protein phosphorylation has an essential role during pre-mRNA splicing. Here we identify two previously unidentified phosphoproteins in the human spliceosomal B complex, namely the pre-mRNA processing factors PRP6 and PRP31, both components of the U4/U6-U5 tri-small nuclear ribonucleoprotein (snRNP). We provide evidence that PRP6 and PRP31 are directly phosphorylated by human PRP4 kinase (PRP4K) concomitant with their incorporation into B complexes.

PRP4 is a spindle assembly checkpoint protein required for MPS1, MAD1, and MAD2 localization to the kinetochores.

The spindle checkpoint delays anaphase onset until every chromosome kinetochore has been efficiently captured by the mitotic spindle microtubules. In this study, we report that the human pre-messenger RNA processing 4 (PRP4) protein kinase associates with kinetochores during mitosis. PRP4 depletion by RNA interference induces mitotic acceleration.