Women in Physics in the Netherlands: Progress and Developments

The visibility of women and the awareness of a healthy gender balance in physics in the Netherlands have clearly improved over the last few years. Initiatives to promote women and their possibilities to pursue a career in physics are plentiful and commendable. Nevertheless, the numbers do not yet show the desired impact of all these initiatives. Although student numbers have increased, the percentage of female first-year student remains at approximately 13% of the total students in physics. Similarly, the relative numbers of female PhD candidates and postdocs have been stable over the last years at (both) approximately 20% to 25%. Despite the number of women obtaining a PhD in physics and continuing a scientific career as postdoc, the presence of women further up on the scientific ladder in physics remains strikingly low. We will here focus on the current status, ambitions, and initiatives in the Netherlands to promote women, and especially to keep them, in physics

Modest proteasomal inhibition by aberrant ubiquitin exacerbates aggregate formation in a Huntington disease mouse model

UBB+1, a mutant form of ubiquitin, is both a substrate and an inhibitor of the proteasome which accumulates in the neuropathological hallmarks of Huntington disease (HD). In vitro, expression of UBB+1 and mutant huntingtin synergistically increase aggregate formation and polyglutamine induced cell death. We generated a UBB+1 transgenic mouse line expressing UBB+1 within the neurons of the striatum. In these mice lentiviral driven expression of expanded huntingtin constructs in the striatum results in a significant increase in neuronal inclusion formation. Although UBB+1 transgenic mice show neither a decreased lifespan nor apparent neuronal loss, they appear to be more vulnerable to toxic insults like expanded polyglutamine proteins due to a modest proteasome inhibition. These findings underscore the relevance of an efficient ubiquitin-proteasome system in HD. (C) 2009 Elsevier Inc. All rights reserved.Pathophysiology of paroxysmal and chronic degenerative progressive disorder of the central and periferal nervous syste

Silencing GFAP isoforms in astrocytoma cells disturbs laminin-dependent motility and cell adhesion

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein expressed in astrocytes and neural stem cells. The GFAP gene is alternatively spliced, and expression of GFAP is highly regulated during development, on brain damage, and in neurodegenerative diseases. GFAPα is the canonical splice variant and is expressed in all GFAP-positive cells. In the human brain, the alternatively spliced transcript GFAPδ marks specialized astrocyte populations, such as subpial astrocytes and the neurogenic astrocytes in the human subventricular zone. We here show that shifting the GFAP isoform ratio in favor of GFAPδ in astrocytoma cells, by selectively silencing the canonical isoform GFAPα with short hairpin RNAs, induced a change in integrins, a decrease in plectin, and an increase in expression of the extracellular matrix component laminin. Together, this did not affect cell proliferation but resulted in a significantly decreased motility of astrocytoma cells. In contrast, a down-regulation of all GFAP isoforms led to less cell spreading, increased integrin expression, and a >100-fold difference in the adhesion of astrocytoma cells to laminin. In summary, isoform-specific silencing of GFAP revealed distinct roles of a specialized GFAP network in regulating the interaction of astrocytoma cells with the extracellular matrix through laminin.-Moeton, M., Kanski, R., Stassen, O. M. J. A., Sluijs, J. A., Geerts, D., van Tijn, P., Wiche, G., van Strien, M. E., Hol, E. M. Silencing GFAP isoforms in astrocytoma cells disturbs laminin dependent motility and cell adhesion

Histone acetylation in astrocytes suppresses GFAP and stimulates a reorganization of the intermediate filament network

Glial fibrillary acidic protein (GFAP) is the main intermediate filament in astrocytes and is regulated by epigenetic mechanisms during development. We demonstrate that histone acetylation also controls GFAP expression in mature astrocytes. Inhibition of histone deacetylases (HDACs) with trichostatin A or sodium butyrate reduced GFAP expression in primary human astrocytes and astrocytoma cells. Because splicing occurs co-transcriptionally, we investigated whether histone acetylation changes the ratio between the canonical isoform GFAPα and the alternative GFAPδ splice variant. We observed that decreased transcription of GFAP enhanced alternative isoform expression, as HDAC inhibition increased the GFAPδ∶GFAPα ratio. Expression of GFAPδ was dependent on the presence and binding of splicing factors of the SR protein family. Inhibition of HDAC activity also resulted in aggregation of the GFAP network, reminiscent of our previous findings of a GFAPδ-induced network collapse. Taken together, our data demonstrate that HDAC inhibition results in changes in transcription, splicing and organization of GFAP. These data imply that a tight regulation of histone acetylation in astrocytes is essential, because dysregulation of gene expression causes the aggregation of GFAP, a hallmark of human diseases like Alexander's diseas

Intermediate filament transcription in astrocytes is repressed by proteasome inhibition

Increased expression of the astrocytic intermediate filament protein glial fibrillary acidic protein (GFAP) is a characteristic of astrogliosis. This process occurs in the brain during aging and neurodegeneration and coincides with impairment of the ubiquitin proteasome system. Inhibition of the proteasome impairs protein degradation; therefore, we hypothesized that the increase in GFAP may be the result of impaired proteasomal activity in astrocytes. We investigated the effect of proteasome inhibitors on GFAP expression and other intermediate filament proteins in human astrocytoma cells and in a rat brain model for astrogliosis. Extensive quantitative RT-PCR, immunocytochemistry, and Western blot analysis resulted unexpectedly in a strong decrease of GFAP mRNA to <4% of control levels [Control (DMSO) 100±19.2%; proteasome inhibitor (epoxomicin) 3.5±1.3%, n=8; P≤0.001] and a loss of GFAP protein in astrocytes in vitro. We show that the proteasome alters GFAP promoter activity, possibly mediated by transcription factors as demonstrated by a GFAP promoter-luciferase assay and RT(2) Profiler PCR array for human transcription factors. Most important, we demonstrate that proteasome inhibitors also reduce GFAP and vimentin expression in a rat model for induced astrogliosis in vivo. Therefore, proteasome inhibitors could serve as a potential therapy to modulate astrogliosis associated with CNS injuries and disease.—Middeldorp, J., Kamphuis, W., Sluijs, J. A., Achoui, D., Leenaars, C. H. C., Feenstra, M. G. P., van Tijn, P., Fischer, D. F., Berkers, C., Ovaa, H., Quinlan, R. A., Hol, E. M. Intermediate filament transcription in astrocytes is repressed by proteasome inhibition