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1.  Comprehensive Analysis of HPV16 Integration in OSCC Reveals No Significant Impact of Physical Status on Viral Oncogene and Virally Disrupted Human Gene Expression 
PLoS ONE  2014;9(2):e88718.
Infection with high-risk human papillomavirus (HPV) type 16 is an independent risk factor for the development of oropharyngeal squamous cell carcinomas (OSCC). However, it is unclear whether viral integration is an essential hallmark in the carcinogenic process of OSCC and whether HPV integration correlates with the level of viral gene transcription and influences the expression of disrupted host genes. We analyzed 75 patients with OSCC. HPV16-positivity was proven by p16INK4A immunohistochemistry, PCR and FISH. Viral integration was examined using DIPS- as well as APOT-PCR. Viral E2, E6 and E7 gene expression levels were quantified by quantitative reverse transcriptase (RT-q)PCR. Expression levels of 7 human genes disrupted by the virus were extracted from mRNA expression profiling data of 32 OSCCs. Viral copy numbers were assessed by qPCR in 73 tumors. We identified 37 HPV16-human fusion products indicating viral integration in 29 (39%) OSCC. In the remaining tumors (61%) only episome-derived PCR products were detected. When comparing OSCC with or without an integration-derived fusion product, we did not find significant differences in the mean RNA expression of viral genes E2, E6 and E7 or the viral copy numbers per cell, nor did the RNA expression of the HPV-disrupted genes differ from either group of OSCC. In conclusion, our data do not support the hypothesis that integration affects the levels of viral and/or HPV-disrupted human gene transcripts. Thus constitutive, rather than a high level, of expression of oncogene transcripts appears to be required in HPV-related OSCC.
PMCID: PMC3933331  PMID: 24586376
2.  Cerebral Accumulation of Dietary Derivable Plant Sterols does not Interfere with Memory and Anxiety Related Behavior in Abcg5−/− Mice 
Plant sterols such as sitosterol and campesterol are frequently applied as functional food in the prevention of atherosclerosis. Recently, it became clear that plasma derived plant sterols accumulate in murine brains. We questioned whether plant sterols in the brain are associated with alterations in brain cholesterol homeostasis and subsequently with brain functions. ATP binding cassette (Abc)g5−/− mice, a phytosterolemia model, were compared to Abcg5+/+ mice for serum and brain plant sterol accumulation and behavioral and cognitive performance. Serum and brain plant sterol concentrations were respectively 35–70-fold and 5–12-fold increased in Abcg5−/− mice (P < 0.001). Plant sterol accumulation resulted in decreased levels of desmosterol (P < 0.01) and 24(S)-hydroxycholesterol (P < 0.01) in the hippocampus, the brain region important for learning and memory functions, and increased lanosterol levels (P < 0.01) in the cortex. However, Abcg5−/− and Abcg5+/+ displayed no differences in memory functions or in anxiety and mood related behavior. The swimming speed of the Abcg5−/− mice was slightly higher compared to Abcg5+/+ mice (P < 0.001). In conclusion, plant sterols in the brains of Abcg5−/− mice did have consequences for brain cholesterol metabolism, but did not lead to an overt phenotype of memory or anxiety related behavior. Thus, our data provide no contra-indication for nutritional intake of plant sterol enriched nutrition.
PMCID: PMC3134714  PMID: 21431910
Abcg5; Anxiety; Cholesterol; Cognition; Phytosterolemia and plant sterol
3.  Reorganization of the nuclear lamina and cytoskeleton in adipogenesis 
Histochemistry and Cell Biology  2011;135(3):251-261.
A thorough understanding of fat cell biology is necessary to counter the epidemic of obesity. Although molecular pathways governing adipogenesis are well delineated, the structure of the nuclear lamina and nuclear-cytoskeleton junction in this process are not. The identification of the ‘linker of nucleus and cytoskeleton’ (LINC) complex made us consider a role for the nuclear lamina in adipose conversion. We herein focused on the structure of the nuclear lamina and its coupling to the vimentin network, which forms a cage-like structure surrounding individual lipid droplets in mature adipocytes. Analysis of a mouse and human model system for fat cell differentiation showed fragmentation of the nuclear lamina and subsequent loss of lamins A, C, B1 and emerin at the nuclear rim, which coincides with reorganization of the nesprin-3/plectin/vimentin complex into a network lining lipid droplets. Upon 18 days of fat cell differentiation, the fraction of adipocytes expressing lamins A, C and B1 at the nuclear rim increased, though overall lamin A/C protein levels were low. Lamin B2 remained at the nuclear rim throughout fat cell differentiation. Light and electron microscopy of a subcutaneous adipose tissue specimen showed striking indentations of the nucleus by lipid droplets, suggestive for an increased plasticity of the nucleus due to profound reorganization of the cellular infrastructure. This dynamic reorganization of the nuclear lamina in adipogenesis is an important finding that may open up new venues for research in and treatment of obesity and nuclear lamina-associated lipodystrophy.
Electronic supplementary material
The online version of this article (doi:10.1007/s00418-011-0792-4) contains supplementary material, which is available to authorized users.
PMCID: PMC3052499  PMID: 21350821
LINC; Fat; Lamin; Adipose tissue; Nesprin-3; Vimentin
4.  Autophosphorylation of Polo-like Kinase 4 and Its Role in Centriole Duplication 
Molecular Biology of the Cell  2010;21(4):547-561.
PLK4 is a key regulator of centriole duplication. Here, we show that PLK4 is active beyond the initiation of centriole duplication with the abundance of active kinase increasing to a peak in mitosis. Importantly, we show that differences in PLK4 abundance exist between mother and daughter centrioles and that active PLK4 is restricted to the centrosome.
Centrosome duplication occurs once every cell cycle in a strictly controlled manner. Polo-like kinase 4 (PLK4) is a key regulator of this process whose kinase activity is essential for centriole duplication. Here, we show that PLK4 autophosphorylation of serine S305 is a consequence of kinase activation and enables the active fraction to be identified in the cell. Active PLK4 is detectable on the replicating mother centriole in G1/S, with the proportion of active kinase increasing through interphase to reach a maximum in mitosis. Activation of PLK4 at the replicating daughter centriole is delayed until G2, but a level equivalent to the replicating mother centriole is achieved in M phase. Active PLK4 is regulated by the proteasome, because either proteasome inhibition or mutation of the degron motif of PLK4 results in the accumulation of S305-phosphorylated PLK4. Autophosphorylation probably plays a role in the process of centriole duplication, because mimicking S305 phosphorylation enhances the ability of overexpressed PLK4 to induce centriole amplification. Importantly, we show that S305-phosphorylated PLK4 is specifically sequestered at the centrosome contrary to the nonphosphorylated form. These data suggest that PLK4 activity is restricted to the centrosome to prevent aberrant centriole assembly and sustained kinase activity is required for centriole duplication.
PMCID: PMC2820420  PMID: 20032307
5.  Nucleoplasmic LAP2α–lamin A complexes are required to maintain a proliferative state in human fibroblasts 
The Journal of Cell Biology  2007;176(2):163-172.
In human diploid fibroblasts (HDFs), expression of lamina-associated polypeptide 2 α (LAP2α) upon entry and exit from G0 is tightly correlated with phosphorylation and subnuclear localization of retinoblastoma protein (Rb). Phosphoisoforms of Rb and LAP2α are down-regulated in G0. Although RbS780 phosphoform and LAP2α are up-regulated upon reentry into G1 and colocalize in the nucleoplasm, RbS795 migrates between nucleoplasmic and speckle compartments. In HDFs, which are null for lamins A/C, LAP2α is mislocalized within nuclear aggregates, and this is correlated with cell cycle arrest and accumulation of Rb within speckles. Nuclear retention of nucleoplasmic Rb during G1 phase but not of speckle-associated Rb depends on lamin A/C. siRNA knock down of LAP2α or lamin A/C in HDFs leads to accumulation of Rb in speckles and G1 arrest, probably because of activation of a cell cycle checkpoint. Our results suggest that LAP2α and lamin A/C are involved in controlling Rb localization and phosphorylation, and a lack or mislocalization of either protein leads to cell cycle arrest in HDFs.
PMCID: PMC2063936  PMID: 17227891
6.  FISH Analysis of Six Chromosomes in Unfertilized Human Oocytes After Polar Body Removal 
Purpose: To develop an improved technique for estimatingchromosomal abnormalities in human oocytes byfluorescence in situ hybridization (FISH) and to correlate theposition of single chromatids with the chromosomal status ofthe oocytes.
Methods: Oocytes that were at metaphase II about17–20 hr after insemination or intracytoplasmic sperm injection(ICSI) were treated with pronase to remove the zonapellucida and polar body (PB) and then spread on slides usingHCl and Tween 20. Two rounds of FISH were performedusing direct-labeled probes: chromosomes 1, 13, 21 (round1); chromosomes X, 7, 18 (round 2).
Results: Of the 63 oocytes from 18 patients (mean age,32 years), 48 (76%) had one DNA complement as expected, 9(14%) had 2 DNA complements, 3 (5%) gave incomplete FISHsignals, and 3 (5%) were not analyzable. Of the 48 oocyteswith one set of DNA, 48% were haploid, 44% were aneuploidfor one or more chromosomes, and 8% were polyploid. Wealso found an increased frequency of predivision of chromatidbivalents in aneuploid oocytes, especially for chromosome 21.
Conclusions: This technique enables simultaneousassessment of six chromosomes in human oocytes, and thereforecan be useful for accurately determining the incidence andcauses of genetic imbalances in human oocytes andapparently low fertilization rates.
PMCID: PMC3455197  PMID: 10976415
aneuploidy; FISH; oocyte; polar body
7.  Accumulation of 3-Ketosteroids Induced by Itraconazole in Azole-Resistant Clinical Candida albicans Isolates 
Antimicrobial Agents and Chemotherapy  1999;43(11):2663-2670.
The effects of itraconazole on ergosterol biosynthesis were investigated in a series of 16 matched clinical Candida albicans isolates which had been previously analyzed for mechanisms of resistance to azoles (D. Sanglard, K. Kuchler, F. Ischer, J. L. Pagani, M. Monod, and J. Bille, Antimicrob. Agents Chemother., 39:2378–2386, 1995). Under control conditions, all isolates contained ergosterol as the predominant sterol, except two strains (C48 and C56). In isolates C48 and C56, both less susceptible to azoles than their parent, C43, substantial concentrations (20 to 30%) of 14α-methyl-ergosta-8,24(28)-diene-3β,6α-diol (3,6-diol) were found. Itraconazole treatment of C43 resulted in a dose-dependent inhibition of ergosterol biosynthesis (50% inhibitory concentration, 2 nM) and accumulation of 3,6-diol (up to 60% of the total sterols) together with eburicol, lanosterol, obtusifoliol, 14α-methyl-ergosta-5,7,22,24(28)-tetraene-3βol, and 14α-methyl-fecosterol. In strains C48 and C56, no further increase of 3,6-diol was observed after exposure to itraconazole. Ergosterol synthesis was less sensitive to itraconazole inhibition, as was expected for these azole-resistant isolates which overexpress ATP-binding cassette transporter genes CDR1 and CDR2. In addition to 3,6-diol, substantial amounts of obtusifolione were found after exposure to itraconazole. This toxic 3-ketosteroid was demonstrated previously to accumulate after itraconazole treatment in Cryptococcus neoformans and Histoplasma capsulatum but has not been reported in Candida isolates. Accumulation of obtusifolione correlated with nearly complete growth inhibition in these azole-resistant strains compared to that found in the susceptible parent strain, although the onset of growth inhibition only occurred at higher concentrations of itraconazole. ERG25 and ERG26 are the only genes assigned to the 4-demethylation process, of which the 3-ketoreductase is part. To verify whether mutations in these ERG25 genes contributed to obtusifolione accumulation, their nucleotide sequences were determined in all three related isolates. No mutations in ERG25 alleles of isolates C48 and C56 were found, suggesting that this gene is not involved in obtusifolione accumulation. The molecular basis for the accumulation of this sterol in these two strains remains to be established.
PMCID: PMC89540  PMID: 10543744

Results 1-7 (7)