Role of microcephalin at mitosis

A large brain is one of the most distinguishing features of humans compared to other members of the animal kingdom. During mammalian evolution there has been a disproportionate enlargement of the brain relative to body size and this expansion has been particularly prominent during the past 3 million years of human lineage. This must be the consequence of adaptive genetic alterations during mammalian evolution, but the genes and molecular processes altered are essentially unknown. One approach for identifying candidate genes for brain size regulation is through characterisation of Mendelian disorders of brain development. In particular, primary microcephaly has received considerable interest as a model disease for studying brain size regulators because patients present with a profoundly reduced brain size but have no other malformations. Genetic studies have identified mutations in seven genes that can cause primary microcephaly. All the primary microcephaly proteins localise to the centrosome at some stage during the cell cycle and have roles in a diverse range of functions including centrosome maturation, centriole formation and microtubule organisation at the spindle pole. The precise mechanism leading to primary microcephaly is not known but a prevalent hypothesis is that centrosome dysfunction disrupts mitosis of neural progenitor cells. Despite there being strong evidence in support of this hypothesis for most primary microcephaly genes, MCPH1 (the first primary microcephaly gene to be identified) always appeared to be functionally distinct from other primary microcephaly proteins. Most work on MCPH1 has focussed on its role in the DNA damage response and cell cycle timing rather than on its mitotic role. As a result, the aim of this thesis is to perform a detailed analysis of MCPH1 function during mitosis. In this thesis, three isoforms of MCPH1 were characterised and their localisation, expression and stability examined. It was established that MCPH1 is highly regulated during mitosis. MCPH1 transcript and protein levels vary significantly throughout the cell cycle and MCPH1 protein is targeted for degradation late in mitosis. In addition, MCPH1 is hyperphosphorylated during mitosis (in prometaphase-arrested cells) suggesting that phosphorylation could potentially regulate MCPH1 mitotic function. Twelve mitotic phosphorylation sites were identified by phosphopeptide mapping, many of which were CDK1 and PLK1 consensus sites. Both PLK1 and CDK1 also contribute to MCPH1 phosphorylation in vivo. Although MCPH1 non-phosphorylatable mutants localise normally during mitosis, binding to interaction partners may be affected which may have functional consequences. During mitosis MCPH1 localises to the centrosomes and kinetochores. Consistent with this localisation, RNAi-mediated knockdown of MCPH1 leads to metaphase arrest with multipolar spindles, major defects in chromosome alignment and loss of chromatid cohesion. In addition, MCPH1 deficient mouse embryonic fibroblast cells also demonstrate similar chromosome alignment defects, strengthening this finding in an independent system. Live-imaging of MCPH1 depleted cells demonstrate that a normal bipolar spindle and metaphase plate are initially formed, but subsequently chromosomes and chromatids drop off the metaphase plate and eventually the spindle collapses. This suggests that the primary function of MCPH1 is to allow timely progression through metaphase, possibly by mediating kinetochore-microtubule attachments to satisfy the spindle activated checkpoint. Therefore my work describes several roles for MCPH1 in mitosis (centrosome stability, chromosome alignment and metaphase progression) suggesting that its role in mitosis could result in primary microcephaly in a number of different ways

Intended Usage of a Healthcare Communication Technology: Focusing on the Role of IT-Related Overload

In this paper we employ a perspective on overload that focuses on information processing rather than on the amount of information an individual receives. To understand how individuals determine whether or not to use a new technology, we introduce a new type of overload: Emotional and Cognitive Overload (ECO). To understand the role of ECO on the adoption and use of a new technology, we develop an Input-Process-Output model which opens up the black box related to the processes leading to overload. In particular, the model distinguishes mental processes from overload’s emotional and cognitive consequences. We test the research model using the results of a large survey (N=2037) that was underwritten by a large Dutch bank that was interested in delivering healthcare information online through the use of a video contact technology (VCT). The study’s findings are significant and support our hypotheses. We report them and discuss the implications

"Women's rights, the European Court and Supranational Constitutionalism"

This analysis examines supranational constitutionalism in the European Union. In particular, the study focuses on the role of the European Court of Justice in the creation of women’s rights. I examine the interaction between the Court and member state governments in legal integration, and also the integral role that women’s advocates – both individual activists and groups – have played in the development of EU social provisions. The findings suggest that this litigation dynamic can have the effect of fueling the integration process by creating new rights that may empower social actors and EU organizations, with the ultimate effect of diminishing member state government control over the scope and direction of EU law. This study focuses specifically on gender equality law, yet provides a general framework for examining the case law in subsequent legal domains, with the purpose of providing a more nuanced understanding of supranational governance and constitutionalism

Mutations in pericentrin cause Seckel syndrome with defective ATR-dependent DNA damage signaling

Large brain size is one of the defining characteristics of modern humans. Seckel syndrome (MIM 210600), a disorder of markedly reduced brain and body size, is associated with defective ATR-dependent DNA damage signaling. Only a single hypomorphic mutation of ATR has been identified in this genetically heterogeneous condition. We now report that mutations in the gene encoding pericentrin (PCNT)--resulting in the loss of pericentrin from the centrosome, where it has key functions anchoring both structural and regulatory proteins--also cause Seckel syndrome. Furthermore, we find that cells of individuals with Seckel syndrome due to mutations in PCNT (PCNT-Seckel) have defects in ATR-dependent checkpoint signaling, providing the first evidence linking a structural centrosomal protein with DNA damage signaling. These findings also suggest that other known microcephaly genes implicated in either DNA repair responses or centrosomal function may act in common developmental pathways determining human brain and body size

Research and Education in Computational Science and Engineering

Over the past two decades the field of computational science and engineering (CSE) has penetrated both basic and applied research in academia, industry, and laboratories to advance discovery, optimize systems, support decision-makers, and educate the scientific and engineering workforce. Informed by centuries of theory and experiment, CSE performs computational experiments to answer questions that neither theory nor experiment alone is equipped to answer. CSE provides scientists and engineers of all persuasions with algorithmic inventions and software systems that transcend disciplines and scales. Carried on a wave of digital technology, CSE brings the power of parallelism to bear on troves of data. Mathematics-based advanced computing has become a prevalent means of discovery and innovation in essentially all areas of science, engineering, technology, and society; and the CSE community is at the core of this transformation. However, a combination of disruptive developments---including the architectural complexity of extreme-scale computing, the data revolution that engulfs the planet, and the specialization required to follow the applications to new frontiers---is redefining the scope and reach of the CSE endeavor. This report describes the rapid expansion of CSE and the challenges to sustaining its bold advances. The report also presents strategies and directions for CSE research and education for the next decade.Comment: Major revision, to appear in SIAM Revie

Minimum Unit Pricing: Qualitative Study of the Experiences of Homeless Drinkers, Street Drinkers and Service Providers

Aims: Alcohol Minimum Unit Pricing (MUP) was introduced in Scotland in May 2018. Existing evidence suggests MUP can reduce drinking in the general population, but there is little evidence regarding its impact on vulnerable groups. This qualitative study aimed to capture the experiences of MUP among homeless drinkers, street drinkers, and the support services that work with them

Polarimetric Imaging of Large Cavity Structures in the Pre-transitional Protoplanetary Disk around PDS 70: Observations of the disk

We present high resolution H-band polarized intensity (PI; FWHM = 0."1: 14 AU) and L'-band imaging data (FWHM = 0."11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0."2) up to 210 AU (1."5). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is ~70 AU. Our data show that the geometric center of the disk shifts by ~6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of SED fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L'-band imaging data, we put an upper limit mass of companions at ~30 to ~50MJ within the gap. Taking account of the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.Comment: accepted by APJ

Cerebral organoids model human brain development and microcephaly

The complexity of the human brain has made it difficult to study many brain disorders in model organisms, and highlights the need for an in vitro model of human brain development. We have developed a human pluripotent stem cell-derived 3D organoid culture system, termed cerebral organoid, which develops various discrete though interdependent brain regions. These include cerebral cortex containing progenitor populations that organize and produce mature cortical neuron subtypes. Furthermore, cerebral organoids recapitulate features of human cortical development, namely characteristic progenitor zone organization with abundant outer radial glial stem cells. Finally, we use RNAi and patient-specific iPS cells to model microcephaly, a disorder that has been difficult to recapitulate in mice. We demonstrate premature neuronal differentiation in patient organoids, a defect that could explain the disease phenotype. Our data demonstrate that 3D organoids can recapitulate development and disease of even this most complex human tissue