Search PubMed⌕ Search

Biomedical subjects

Markus Hengstschläger

Publications and source records attributed to Markus Hengstschläger.

At least 19 recordsLinked to original sources
PubMed2006

The tuberous sclerosis genes and regulation of the cyclin-dependent kinase inhibitor p27.

Tuberous sclerosis complex (TSC) is an autosomal dominant tumor syndrome that affects approximately 1 in 6000 individuals. It is characterized by the development of tumors, named hamartomas, in the kidneys, heart, skin and brain. The latter often cause seizures, mental retardation, and a variety of developmental disorders, including autism. This disease is caused by mutations within the tumor suppressor gene TSC1 on chromosome 9q34 encoding hamartin or within TSC2 on chromosome 16p13.3 encoding tuberin. TSC patients carry a mutant TSC1 or TSC2 gene in each of their somatic cells, and loss of heterozygosity has been documented in a wide variety of TSC tumors. Recent data suggest that functional inactivation of TSC proteins might also be involved in the development of other diseases not associated with TSC, such as sporadic bladder cancer, breast cancer, ovarian carcinoma, gall bladder carcinoma, non-small-cell carcinoma of the lung, and Alzheimer's disease. Tuberin and hamartin form a heterodimer, suggesting they might affect the same processes. Tuberin is assumed to be the functional component of the complex and has been implicated in the regulation of different cellular functions. The TSC proteins regulate cell size control due to their involvement in the insulin signalling pathway. Furthermore, they are potent positive regulators of the cyclin-dependent kinase inhibitor p27, a major regulator of the mammalian cell cycle. Here we review the current knowledge on how mutations within the TSC genes could trigger deregulation of stability and localization of the tumor suppressor p27.

Cyclin-Dependent Kinase Inhibitor p27↗
PubMed2006

Differentiation-dependent expression of hypothetical proteins in the neuroblastoma cell line N1E-115.

Several protein cascades, including signaling, cytoskeletal, chaperones, metabolic, and antioxidant proteins, have been shown to be involved in the process of neuronal differentiation (ND) of neuroblastoma cell lines. No systematic approach to detect hitherto unknown and unnamed proteins or structures that have been predicted upon nucleic acid sequences in ND has been published so far. We therefore decided to screen hypothetical protein (HP) expression by protein profiling. Two-dimensional gel electrophoresis with subsequent matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF/TOF) identification was used for expression analysis of undifferentiated and dimethylsulfoxide-induced neuronally differentiated N1E-115 cells. We unambiguously identified six HPs: Q8C520, Q99LF4, Q9CXS1, Q9DAF8, Q91WT0, and Q8C5G2. A prefoldin domain in Q91WT0, a t-SNARE domain in Q9CXS1, and a bromodomain were observed in Q8C5G2. For the three remaining proteins, no putative function using Pfam, BLOCKS, PROSITE, PRINTS, InterPro, Superfamily, CoPS, and ExPASy could be assigned. While two proteins were present in both cell lines, Q9CXS1 was switched off (i.e., undetectably low) in differentiated cells only, and Q9DAF8, Q91WT0, and Q8C5G2 were switched on in differentiated cells exclusively. Herein, using a proteomic approach suitable for screening and identification of HP, we present HP structures that have been only predicted so far based upon nucleic acid sequences. The four differentially regulated HPs may play a putative role in the process of ND.

Amino Acid Sequence↗
PubMed2006

Bach2 is involved in neuronal differentiation of N1E-115 neuroblastoma cells.

Bach1 and Bach2 are evolutionarily related members of the BTB-basic region leucine zipper transcription factor family. We found that Bach2 downregulates cell proliferation of N1E-115 cells and negatively affects their potential to differentiate. Nuclear localization of the cyclin-dependent kinase inhibitor p21 is known to arrest cell cycle progression, and cytoplasmic p21 has been shown to promote neuronal differentiation of N1E-115 cells. We found that ectopic Bach2 causes upregulation of p21 expression in the nucleus and in the cytoplasm in undifferentiated N1E-115 cells. In differentiated cells, Bach2 specifically triggers upregulation of cytoplasmic p21. Our data suggest that Bach2 expression could represent a switch during the process of neuronal differentiation. Bach2 is not expressed in neuronal precursor cells. It would have negative effects on proliferation and differentiation of these cells. In differentiated neuronal cells Bach2 expression is upregulated, which could allow Bach2 to function as a gatekeeper of the differentiated status.

Animals↗
PubMed2006

Fetal magnetic resonance imaging and human genetics.

The use of fetal magnetic resonance imaging (MRI), in addition to prenatal genetic testing and sonography, has the potential to improve prenatal diagnosis of genetic disorders. MRI plays an important role in the evaluation of fetal abnormalities and malformations. Fetal MRI often enables a differential diagnosis, a determination of the extent of the disorder, the prognosis, and an improvement in therapeutic management. For counseling of parents, as well as to basically understand how genetic aberrations affect fetal development, it is of great importance to correlate different genotypes with fetal MRI data.

Biomarkers↗
PubMed2005

Subtelomeric rearrangements as neutral genomic polymorphisms.

Submicroscopic chromosomal rearrangements affecting telomeres are important aetiological contributors to the development of mental retardation. Results from over 2,500 analysed patients with mental retardation demonstrated that about 5% have a subtelomeric aberration. However, some subtelomeric rearrangements have no phenotypic consequences. Due to the heterogeneity of such rearrangements and to the limited information about which monosomy or trisomy can be tolerated without phenotypic effect, conclusions about the association of a specific aberration and the phenotypical consequences are often hard to draw. We performed a study of subtelomeric aberrations with the aim to provide more insights into the understanding of such rearrangements as neutral genomic polymorphisms. We found two new polymorphisms: a duplication or triplication of the subtelomeric region of the long arm of chromosome 4 and a trisomy of the subtelomeric region of the short arm of chromosome 6 owing to a transposition to chromosome 22. These new data are presented and discussed in the context of the published literature.

Child↗
PubMed2005

Differentiation of neuroblastoma cell line N1E-115 involves several signaling cascades.

No systematic searches for differential expression of signaling proteins (SP) in undifferentiated vs. differentiated cell lineages were published and herein we used protein profiling for this purpose. The NIE-115 cell line was cultivated and an aliquot was differentiated with dimethylsulfoxide (DMSO), that is known to lead to a neuronal phenotype. Cell lysates were prepared, run on two-dimensional gel electrophoresis followed by MALDI-TOF-TOF identification of proteins and maps of identified SPs were generated. Seven SPs were comparable, 27 SPs: GTP-binding/Ras-related proteins, kinases, growth factors, calcium binding proteins, phosphatase-related proteins were observed in differentiated NIE-115 cells and eight SPs of the groups mentioned above were observed in undifferentiated cells only. Switching-on/off of several individual SPs from different signaling cascades during the differentiation process is a key to understand mechanisms involved. The findings reported herein are challenging in vitro and in vivo studies to confirm a functional role for deranged SPs.

Brain Neoplasms↗
PubMed2005

Tuberin--a new molecular target in Alzheimer's disease?

Tuberous sclerosis complex (TSC) is a common genetic disorder in which affected individuals develop mental retardation, developmental brain defects and seizures. The TSC gene products, hamartin and tuberin, form a complex, of which tuberin is assumed to be the functional component being involved in a wide variety of different cellular processes. Here we report that tuberin protein levels are decreased in the frontal cortex of patients with Alzheimer's disease. In addition, tuberin levels are also decreased in Down syndrome brain samples positive for beta-amyloid plaques and neurofibrillary tangles. Analysis of NeuN revealed that this regulation is not a consequence of differences in the amount of postmitotic neurons. This first connection of tuberin to another common disease beside TSC stimulates new approaches to investigate the molecular development and to establish new therapeutic strategies.

Aged↗
PubMed2005

The cellular response to ectopic overexpression of the tuberous sclerosis genes, TSC1 and TSC2: a proteomic approach.

The genes, TSC1 on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13.3, encoding tuberin, are responsible for tuberous sclerosis (TSC). TSC is an autosomal dominant tumor suppressor gene syndrome affecting about 1 in 6000 individuals. It is characterized by mental retardation and epilepsy. A variety of tumors characteristically occur in different organs of TSC patients and are believed to result from defects in cell cycle/cell size control. Hamartin and tuberin form a complex providing a tentative explanation for the similar disease phenotype in TSC patients with mutations in either of these genes. Beside overlap in many features of patients with TSC1 and TSC2 mutations, data accumulated providing evidence for specific clinical differences. In this study, we performed a proteomic approach of two-dimensional gel electrophoresis with subsequent mass spectrometrical identification of protein spots after ectopic overexpression of human TSC1 or TSC2. We found the protein levels of the calumenin precursor; the complement component 1; heterogeneous nuclear ribonucleoproteins, C1/C2; heterogeneous nuclear ribonucleoprotein, C1-like protein; nascent polypeptide-associated complex-alpha; proteasome subunit alpha type 5; reticulocalbin 1 precursor; translationally-controlled tumor protein; UV excision repair protein, RAD23 homolog B; elongation factor 1-delta; and the eukaryotic initiation factors, eIF-4A-like NUK-34 and eIF-6; to be deregulated upon ectopic TSC gene expression. These findings suggest that deregulation of the control of these new target proteins might contribute to the development of tubers/hamartomas in tuberous sclerosis patients. The data are presented and discussed in the context of the published literature on proteomic approaches for the identification of targets of the TSC genes.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2005

The tuberous sclerosis genes, TSC1 and TSC2, trigger different gene expression responses.

Tuberous sclerosis (TSC) is an autosomal dominant tumor suppressor gene syndrome affecting about 1 in 6000 individuals. It is characterized by mental retardation and epilepsy. A variety of tumors characteristically occur in different organs of TSC patients. The genes, TSC1 on chromosome 9q34, encoding hamartin, and TSC2 on chromosome 16p13.3, encoding tuberin are responsible for TSC. Hamartin and tuberin form a complex providing a tentative explanation for the similar disease phenotype in TSC patients with mutations in either of these genes. Besides overlap in many features of patients with TSC1 and TSC2 mutations, data accumulated provide evidence for specific clinical differences. Here, we performed microarray analyses of the gene expression response to overexpressed TSC1 or TSC2 in HeLa cells. Out of 2400 analysed genes we found 115 genes to be up-regulated > or =2-fold upon ectopic TSC1 overexpression and 284 genes to be up-regulated > or =2-fold via TSC2. Only 34 of these genes were up-regulated by both, TSC1 and TSC2. Whereas only 7 genes were down-regulated > or =2-fold via TSC1, ectopic TSC2 triggered a > or =2-fold down-regulation of 113 genes. Only 3 of these genes were down-regulated by TSC1 and TSC2. This study provides new insights into the cellular roles of TSC proteins and promotes discussion on whether separable functions of these proteins might be associated with the clinical differences of TSC1- and TSC2-associated disease.

Down-Regulation↗
PubMed2005

Activation of ectopic Oct-4 and Rex-1 promoters in human amniotic fluid cells.

Recently, amniotic fluid was suggested as a new source for stem-cell research and tissue engineering approaches. In order to enable isolation of stem cells and establishment of lines of such cells with an undifferentiated phenotype we have introduced green fluorescent protein regulated by the promoters of the stem cell-specific genes, Oct-4 or Rex-1, into human amniotic fluid cells. For the introduction of DNA into human amniotic fluid cells, we have optimized a specific transfection protocol. We found that human amniotic fluid contains cell populations which are able to activate these promoters. These undifferentiated cells expressing green fluorescent protein can be analysed on a flow cytometer. In addition, we have introduced a plasmid harboring a neomycin-resistance gene under the control of the Oct-4 promoter. G418 selection allowed the isolation of undifferentiated stem cells expressing Oct-4 protein out of human amniotic fluid samples. Our findings confirm the existence of stem cells within amniotic fluid. In addition, the ability to transfect human amniotic fluid cells and to isolate stem-cell marker-positive cells will provide the means to study and manipulate these cells for the purpose of basic and applied research.

Amniotic Fluid↗
PubMed2004

Tuberin binds p27 and negatively regulates its interaction with the SCF component Skp2.

TSC1 (tuberous sclerosis complex 1) encoding hamartin and TSC2 encoding tuberin are tumor suppressor genes responsible for the autosomal dominantly inherited disease tuberous sclerosis. These genes have been demonstrated to negatively regulate cell cycle progression, the activity of cdk2, and the degradation of the cyclin-dependent kinase inhibitor p27. To date, the underlying molecular mechanism remains elusive. Here, we show that tuberin binds to p27. Whereas tuberin also binds p27 in TSC1-negative cells, hamartin does not bind p27 without tuberin. p27 protein levels are regulated through ubiquitin-dependent degradation. Skp2 is the F-box protein, which, together with other proteins, forms an SCF (Skp1/cullin/F-box protein)-type E3 ubiquitin ligase complex whose task is to target p27 for degradation by the proteasome. We found that neither tuberin nor hamartin are in a complex with Skp2. Tuberin does not affect Skp2 protein levels, and the SCFSkp2 ubiquitin ligase does not regulate tuberin stability. But binding of tuberin to p27 sequesters p27 from Skp2 accompanied by an up-regulation of the p27 interaction with cdk2. Skp2-induced p27 degradation and cell cycle progression is abolished by tuberin's protective binding to p27. This work, the first description of the direct interaction of a tumor suppressor protein with p27, provides a molecular explanation for the effects of tuberous sclerosis complex genes on the cell cycle and demonstrates a new aspect of the SCFSkp2-mediated regulation of p27 stability.

Animals↗
PubMed2004

Protein levels of alpha1-tubulin, protein disulfide isomerase, tropomyosins and vimentin are regulated by the tuberous sclerosis gene products.

Tuberous sclerosis (TSC) is an autosomal dominant tumour suppressor gene syndrome affecting about 1 in 6000 individuals. It is characterized by mental retardation and epilepsy. A variety of tumours characteristically occur in different organs of TSC patients. Typically, highly epileptogenic dysplastic lesions (tubers) composed of abnormal shaped neurones can be detected in the cerebral cortex. Two tumour suppressor genes have been shown to be responsible for this disease: TSC1, encoding hamartin, and TSC2, encoding tuberin. In this study we performed a proteomic approach of two-dimensional gel electrophoresis with subsequent mass spectrometrical identification of protein spots after ectopic overexpression of human TSC1 or TSC2. We found the protein levels of alpha1-tubulin, protein disulfide isomerase, tropomyosin 3 and 5 and vimentin to be regulated by the two tuberous sclerosis gene products. The here presented findings suggest that deregulation of the control of these target proteins might contribute to the development of tumours in tuberous sclerosis patients. These data provide important new insights into the molecular development of this disease especially since alpha1-tubulin, protein disulfide isomerase and certain tropomyosins have also been implicated in the regulation of neuronal differentiation.

Blotting, Western↗
PubMed2004

Chromosomal translocation t(10;11)(q26;q13) in a woman with combined pituitary hormone deficiency.

We describe the case of a girl with combined pituitary hormone deficiency (CPHD) carrying a balanced chromosomal translocation t(10;11)(q26;q13) with paternal transmission. Her father, with no apparent physical abnormalities, had the karyotype: 46, XY, t(10;11)(q26;q13). CPHD denotes impaired production of growth hormone (GH) and one or more of the other five anterior pituitary-derived hormones. Pit-1 gene and Prop-1 gene mutations and deletions have been reported being responsible for CPHD. Although our patient had a t(10;11) (q26q13) paternal chromosomal translocation, the phenotype was similar to that found in humans with different Pit-1 or Prop-1 gene alterations. Interestingly, the patient's father had the same translocation without phenotypic effects. In conclusion, we describe panhypopituitarism in a woman with a paternally transmitted translation, which appears to be phenotypically expressed only in females.

Adult↗
PubMed2004

Prenatal diagnosis of tetrasomy 9p with Dandy-Walker malformation.

OBJECTIVES: To add to the knowledge of chromosomal abnormalities associated with Dandy-Walker malformation. METHODS: Molecular cytogenetic analyses of a chorionic villus sampling and of an amniocentesis of a fetus with Dandy-Walker malformation and abnormal somatic development. RESULTS: All cells examined showed a 47, XY, +idic(9p)(pter-->q12::q12-->pter) de novo karyotype. This report describes the fourth case of a tetrasomy 9p associated with Dandy-Walker malformation. CONCLUSIONS: This case, together with the three previously reported cases of an association with a tetrasomy 9p, indicate that this chromosomal aberration should be looked for when Dandy-Walker malformation is detected via prenatal ultrasonography.

Adult↗
PubMed2004

Proteomic determination of metabolic enzymes of the amnion cell: basis for a possible diagnostic tool?

Amniocentesis is a valuable and standard procedure for prenatal diagnosis of genetic or inborn errors of metabolism. Amnion cells are cultivated and chromosomes or proteins can be examined to provide molecular diagnosis. Mainly individual proteins are searched for based upon pedigrees and/or anamnesis. As inborn errors of metabolism involve a vast diversity of metabolic enzymes, we aimed to find a screening method for a large series of metabolic enzymes. Amnion cells were obtained from amniocentesis and subjected to proteomic analysis. We used two-dimensional gel electrophoresis with in-gel digestion followed by matrix-assisted laser desorption/ionization-time of flight analysis, to identify metabolic enzymes. Furthermore, we compared metabolic proteins in amnion cells from controls with those from Down Syndrome (DS). Enzymes involved in carbohydrate handling, amino acid handling, -purine metabolism and intermediary metabolism as well as miscellaneous metabolic pathways were detected. Protein levels of several enzymes were significantly deranged in samples obtained from patients with DS. This approach, with the advantage of the concomitant determination of many enzyme proteins, may form the basis for future metabolic screens when amniocentesis is carried out.

Amniocentesis↗
PubMed2004

Neurogenic cells in human amniotic fluid.

OBJECTIVE: The purpose of this study was to determine whether human amniotic fluid contains cells that harbor the potential to differentiate into neurogenic cells. STUDY DESIGN: Amniotic fluid cells (uncultivated or cultivated in standard or in neurogenic differentiation medium) were analyzed for morphologic neurogenic differentiation and for expression of cluster of differentiation 133 (marker for neuronal stem cells), nestin (neuronal progenitor cells), neurofilament (neurons), the p75 common neurotrophin receptor, the brain-derived neurotrophic factor and neurotrophin-3 and cyclic nucleotide phosphodiesterase (oligodendrocytes). RESULTS: The appearance of neurogenic cells was not detected in uncultivated cells, was sporadic after cultivation in standard medium but strongly increased in neurogenic differentiation medium, and was accompanied by the induction of the expression of the analyzed marker genes. CONCLUSION: For the first time, this study provides evidence that human amniotic fluid contains cells that express markers for neuronal stem and progenitor cells, which harbor the potential to differentiate into neurogenic cells.

AC133 Antigen↗
PubMed2004

FAS (CD95) mutations are rare in gastric MALT lymphoma but occur more frequently in primary gastric diffuse large B-cell lymphoma.

A loss of FAS (CD95) function has been proposed to constitute an important step in early mucosa-associated lymphoid tissue (MALT) lymphoma development and FAS mutations have been recognized in malignant lymphomas, in particular at extranodal sites. Since primary gastric lymphomas frequently exhibit resistance to FAS-mediated apoptosis, we investigated whether FAS is mutated in 18 gastric MALT lymphomas and 28 diffuse large B-cell lymphomas (DLBCL). We detected seven mutations in five lymphomas, one MALT lymphoma and four DLBCL; two DLBCL had two mutations. The MALT lymphoma exhibited a point mutation in the splice donor region of intron 3. Three DLBCL had missense mutations in exon 2, which encodes a signal peptide and a portion of the extracellular FAS ligand-binding domain. One DLBCL carried a point mutation in the splice donor region of intron 8, which would result in exon skipping. Two DLBCL harbored a missense mutation in exon 9, which encodes the intracellular death domain. The two death domain mutations inhibited FAS ligand-induced apoptosis in a dominant-negative mode, when transiently expressed in human T47D breast carcinoma and Jurkat T cells. A signal peptide and an extracellular domain mutation, however, failed to inhibit apoptosis in these transfection assays. They are likely to reduce apoptosis in lymphoma cells solely by a loss of function. In summary, our data show that FAS mutations are rare in primary gastric MALT lymphomas (5.6%) but occur in a subset of primary gastric DLBCL (14.3%) and suggest that these mutations contribute to the pathogenesis of gastric lymphomas by rendering lymphocytes resistant to apoptosis.

Apoptosis↗