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Search Results: 1 - 10 of 31002 matches for " Thomas Liehr "
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Cytogenetic contribution to uniparental disomy (UPD)
Thomas Liehr
Molecular Cytogenetics , 2010, DOI: 10.1186/1755-8166-3-8
Abstract: Uniparental disomy (UPD) is the presence of a chromosome pair derived only from one parent present in a disomic cell line [1]. When one of the first proven UPD case was published [2] an editorial in the same journal issue commented this by the words: < it seems unlikely that UPD will turn out to be anything but an interesting rarity > [3]. However, today, some 20 years later, there are > 1,100 reports on UPD cases [1] and what was considered initially as something exotic is nowadays an important diagnostic [4] and even prognostic factor for special syndromes [5,6]. Also UPD is able to support the localization of monogenic disorder genes (e.g. [7], see also [1]) and was demonstrated to play a role in tumorigenesis, as reviewed by [8].The concept of UPD was introduced in 1980 into medical genetics by Eric Engel [9]. In 1987 the first case of UPD proven by molecular methods was described [10]. However, cases having a UPD were reported before [11-14].In theory there are 48 possible uniparental chromosomal pairs, plus 2 whole genomic variants of UPD which could exist. Up to present no maternal UPD was reported for chromosome 19 (and Y), and no paternal UPD for chromosomes 4, 17, 18 and 19 [1]. UPD can be detected based on cytogenetic data and chromosomal heteromorphisms or rearrangements [10-14], microsatellite analysis [15], methylation test [16] or SNP-bases array-comparative genomic hybridization [15]. Also molecular cytogenetics taking advantage of the so called copy number variations (CNV) within the human genome can be used to characterize UPD [17]. Interestingly, UPD is in at least 30% of the case observed together with a chromosomal aberration [1]. Thus, (molecular) cytogenetics is essential when concentrating on this putatively exclusive molecular genetic topic.This review focuses on UPD present in clinically normal and clinically abnormal persons. UPD cases nowadays repeatedly reported as acquired, tumor-specific epigenetic alteration [8] are not subject of thi
A novel cytogenetic abnormality r(7)(::p11.2->q36.3::) in a Philadelphia-positive chronic myeloid leukemia case  [PDF]
Walid Al Achkar, Abdulsamad Wafa, Abdulmunim Aljapawe, Moneeb Abdullah Kassem Othman, Thomas Liehr
Case Reports in Clinical Medicine (CRCM) , 2013, DOI: 10.4236/crcm.2013.29135
Abstract:

The so-calledPhiladelphia(Ph) chromosome is present in more than 90% of chronic myeloid leukemia (CML) cases. It results in juxtaposition of the 5' part of the BCR gene on chromosome 22 and the 3' part of the ABL1 gene on chromosome 9. An additional acquired monosomy 7 or deletion of 7q is associated with poor prognosis in a variety of myeloid disorders. Here we report a novel Ph chromosome positive CML case with a ring chromosome 7 [r(7)]. Immunophenotyping was compatible with CML, although 4.5% of total leucocytes appeared like acute myelogeneous leukemia (AML) subtype M2. The r(7) was characterized in detail by array-proven multicolor banding (aMCB), the latter being of enormous significance to characterize breakpoint regions in detail. Underlying mechanisms and prognostic are discussed, as ring chromosomes are rare cytogenetic abnormalities in hematopoietic malignancies.

Partial Trisomy 1q21-qter and Partial Monosomy 7q21-qter Due to a Derivative Chromosome 7 in Myelodysplastic Syndrome Associated with Squamous Cell Carcinoma: Case Report  [PDF]
Abdulsamad Wafa, Faten Moassass, Thomas Liehr, Abdulmunim Aljapawe, Walid Al Achkar
Case Reports in Clinical Medicine (CRCM) , 2016, DOI: 10.4236/crcm.2016.512066
Abstract: Background: Myelodysplastic syndromes (MDS) are subtypes of hematological disorders which are known to have partial bone marrow dysplasia, peripheral cytopenia, and later on an increased risk to develop acute myeloid leukemia. Chromosomal aberrations are detected in ~50% of cases of de novo MDS cases and the most common chromosomal abnormalities of this entity include complete or partial monosomy of chromosomes 5 and 7, partial deletion of 20q and 12p, trisomy 8, and 11q23 aberrations. A few primary and/or secondary MDS cases combined with other cancer have been reported. Case Presentation: We report here an adult MDS associated with squamous cell carcinoma (SCC). G-banding and array-proven multicolor banding (aMCB) revealed an unbalanced translocation der(7)t(1;7)(q21;q21), which led to 1q partial trisomy and 7q partial monosomy. Immunophenotype of this case was consistent with refractory anemia with excess of blasts (RAEB-2) according to World Health Organization (WHO) classification. Conclusions: As far as we know, this is the first adult MDS case associated with SCC and an unbalanced translocation t(1;7). Our patient received first cycle of azacitidine treatment and he showed bilateral pleural effusion as a secondary event. This toxicity is not limited to the first cycle as in previous MDS cases; our case is the first one to shown this toxicity as a secondary event of azacitidine treatment. As less than 10 cytogenetcially comparable cases without SCC were reported before in male MDS, we carefully conclude that this cytogenetic aberration may be a hint on a new gender associated MDS subgroup.
C-type lectins and human epithelial membrane protein1: Are they new proteins in keratin disorders?  [PDF]
Nilüfer Karadeniz, Thomas Liehr, Kristin Mrasek, Ibrahim A??k, Zuleyha A??k, Nadezda Kosyakova, Hasmik Mkrtchyan
Open Journal of Genetics (OJGen) , 2013, DOI: 10.4236/ojgen.2013.34029
Abstract:

Here we report a family with a clinical spectrum of Pachyonychia Congenita Tarda (PCT) encompassing two generations via a balanced chromosomal translocation between 4q26 and 12p12.3. We discuss the effects of chromosomal translocations on gene expression through involved breakpoints and structural gene abnormalities detected by array CGH. We believe that the family we present gives further insight to the better understanding of molecular and structural basis of keratin disorders, and to the late onset and genetic basis of PCT through the possible role of C-type lectins and human epithelial membrane protein1 (EMP1). Better understanding of the molecular basis of keratin disorders is the foundation for improved diagnosis, genetic counseling and novel therapeutic approaches to overcome the current treatment limitations related to this disease.

Partial trisomy 9p22 to 9p24.2 in combination with partial monosomy 9pter in a Syrian girl
Walid Al Achkar, Abdulsamad Wafa, Faten Moassass, Thomas Liehr
Molecular Cytogenetics , 2010, DOI: 10.1186/1755-8166-3-18
Abstract: Chromosomes of a young female were analyzed due to primary amenorrhea, short stature, developmental delay and a characteristic facial appearance. Cytogenetic analysis using GTG banding identified a karyotype 46, XX, add(9pter). Surprisingly the application of high resolution molecular cytogenetic techniques characterized a partial trisomy 9p24.2-p22 and partial monosomy 9pter-p24.2. To the best of our knowledge only four similar case were reported by now.Attempts for genotype-phenotype correlations for partial trisomy 9p might have been hampered by the fact that more complex, cryptic aberrations were neither considered nor detected in comparable clinical cases.Trisomy 9p is the fourth most frequent chromosome anomaly in life-born after trisomy 21, 18 and 13. A possible explanation might be that these chromosomes as well as 9p are relatively gene poor [1-3]. The first case of trisomy 9p was described in 1970 [1]. Since then, more than 150 patients with partial or complete trisomy 9p have been reported and this kind of chromosomal imbalance was characterized as a clinically recognizable syndrome. In most patients, the trisomic segment was transmitted from a parent carrying a reciprocal balanced translocation and only a small number arose from de novo duplications [3]. Rearrangements involving the distal region of the short arm of chromosome 9 (9p22 to 9p24) are well described and may involve deletions or duplications resulting in the partial monosomy [4] or the partial trisomy 9p syndrome [3]. Characteristic clinical features of partial trisomy 9p are mental retardation of various degree, short stature, craniofacial abnormalities, short fingers, simian crease, and single crease of the fifth finger. Additional symptoms like microcephaly, cleft lip and palate, malformed ears, and skeletal, nail, cardiac, and genital anomalies have also been observed [3]. Partial monosomy 9p or deletion 9p is also reported to be associated with a well defined phenotype characterized by m
Gain of Chromosome 4qter and Loss of 5pter: An Unusual Case with Features of Cri du Chat Syndrome
Frenny Sheth,Naresh Gohel,Thomas Liehr,Olakanmi Akinde
Case Reports in Genetics , 2012, DOI: 10.1155/2012/153405
Abstract:
Common Fragile Sites: Genomic Hotspots of DNA Damage and Carcinogenesis
Ke Ma,Li Qiu,Kristin Mrasek,Jun Zhang,Thomas Liehr,Luciana Gon?alves Quintana,Zheng Li
International Journal of Molecular Sciences , 2012, DOI: 10.3390/ijms130911974
Abstract: Genomic instability, a hallmark of cancer, occurs preferentially at specific genomic regions known as common fragile sites (CFSs). CFSs are evolutionarily conserved and late replicating regions with AT-rich sequences, and CFS instability is correlated with cancer. In the last decade, much progress has been made toward understanding the mechanisms of chromosomal instability at CFSs. However, despite tremendous efforts, identifying a cancer-associated CFS gene (CACG) remains a challenge and little is known about the function of CACGs at most CFS loci. Recent studies of FATS (for Fragile-site Associated Tumor Suppressor), a new CACG at FRA10F, reveal an active role of this CACG in regulating DNA damage checkpoints and suppressing tumorigenesis. The identification of FATS may inspire more discoveries of other uncharacterized CACGs. Further elucidation of the biological functions and clinical significance of CACGs may be exploited for cancer biomarkers and therapeutic benefits.
Novel complex translocation involving 5 different chromosomes in a chronic myeloid leukemia with Philadelphia chromosome: a case report
Walid Al Achkar, Abdulsamad Wafa, Hasmik Mkrtchyan, Faten Moassass, Thomas Liehr
Molecular Cytogenetics , 2009, DOI: 10.1186/1755-8166-2-21
Abstract: Here we report an exceptional CML case with complex chromosomal aberrations not observed before, involving a 5 chromosome translocation implying chromosomal regions such as 1q42, 4p14 and 5q31 besides 9q34 and 22q11.2.The reported rearrangement developed most probably in one initial step and had no influence on a good response during Imatinib treatment.Chronic myeloid leukemia (CML), a clonal myeloproliferative disease is known to develop from a pluripotent bone-marrow stem cell following the typical BCR and ABL somatic gene rearrangement. In 90-95% of cases with CML, the BCR/ABL fusion gene is the result of reciprocal translocation between chromosomes 9 and 22 and is cytogenetically observable as a small derivative chromosome 22 which is known as Philadelphia (Ph1) chromosome [1,2].In a Ph-positive CML expression of the BCR/ABL chimeric protein p210 with an increased tyrosine kinase activity is essential for multiple signaling pathways to confer the leukemia phenotype [3]. Imatinib mesylate (Glivec, formerly STI571) was designed specifically to inhibit the tyrosine kinase activity of the bcr/abl protein and other tyrosine kinases such as c-abl, c-kit and platelet-derived growth factor receptor. By binding to an active site of the tyrosine kinase, Imatinib mesylate switches off downstream signaling, cells stop proliferating and apoptosis ensues [4]. Many studies have shown a high efficiency of Imatinib therapy to achieve a complete or major cytogenetic response, i.e. 0-34% Ph-positive cells. This positive effect may be achieved in cases with simple t(9;22), and complex translocations resulting in a BCR/ABL fusion gene, as well as in cases with cytogenetic clonal evolution [5,6].Complex chromosomal rearrangements involving one or more additional chromosomes were described in >600 cases with CML [7]. By conventional cytogenetic analysis, two variant subgroups have traditionally been recognized: complex, t(9;22;V), where V represents a third translocation partner chrom
The hierarchically organized splitting of chromosomal bands for all human chromosomes
Nadezda Kosyakova, Anja Weise, Kristin Mrasek, Uwe Claussen, Thomas Liehr, Heike Nelle
Molecular Cytogenetics , 2009, DOI: 10.1186/1755-8166-2-4
Abstract: Here we present for the first time the hierarchically organized splitting of chromosomal bands in their sub-bands for all human chromosomes. To do this, array-proved multicolor banding (aMCB) probe-sets for all human chromosomes were applied to normal metaphase spreads of three different G-band levels. We confirmed for all chromosomes to be a general principle that only Giemsa-dark bands split into dark and light sub-bands, as we demonstrated previously by chromosome stretching. Thus, the biological band splitting is in > 50% of the sub-bands different than implemented by the ISCN nomenclature suggesting also a splitting of G-light bands. Locus-specific probes exemplary confirmed the results of MCB.Overall, the present study enables a better understanding of chromosome architecture. The observed difference of biological and ISCN band-splitting may be an explanation why mapping data from human genome project do not always fit the cytogenetic mapping.The biological nature of hierarchically organized splitting of bands of human chromosomes remained an enigma since the first banding methods were described in 1970 and 1971. The technique introduced by Lore Zech in Caspersson's laboratory involved quinacrine mustard (Q-banding) and fluorescence microscopy [1], while other used Giemsa (G-banding) [2,3]. Though several methods producing chromosome bands were developed later, G-banding became the one most widely used. A uniform system of human chromosomal nomenclature, which allowed to design not only individual chromosomes but also chromosome regions and bands, was proposed for the first time in 1971 at the Fourth International Congress of Human Genetics in Paris [4], later it developed into the document entitled "An International System for Human Cytogenetic Nomenclature", the last edition of which was published in 2005 [5]. Although recently evolved molecular cytogenetic techniques [6-8] and array-CGH [9] allow precise characterization of chromosomal abnormalities, analys
A new open access journal for a rapidly evolving biomedical field: introducing Molecular Cytogenetics
Yuri B Yurov, Thomas Liehr, Lisa G Shaffer, Ivan Y Iourov, Svetlana G Vorsanova
Molecular Cytogenetics , 2008, DOI: 10.1186/1755-8166-1-1
Abstract: -Lev D. Landau, Nobel Prize laureateWelcome to Molecular Cytogenetics. We are proud to introduce you to a new home for biomedical research focused on all aspects of chromosome biology and applications of molecular cytogenetic techniques in all areas of biomedicine. Molecular Cytogenetics [1] represents the first open access source for research concerning molecular cytogenetic techniques. Molecular Cytogenetics will be a valuable resource for researchers all over the world, both those who are already experts and those entering the field.Molecular cytogenetics comprises a set of the techniques operating with either the entire genome or with specific DNA sequences to study genome structure and functions at the chromosomal level. Molecular cytogenetics can also be defined as a specific focus of biomedical sciences targeted at studying chromosomes at molecular and single-cell resolutions and at all stages of the cell cycle. Furthermore, the area of molecular cytogenetic technique applications has come to encompass almost everything from applied research in clinical and cancer genetics to basic studies in cellular and structural biology, genomics, genetics, and neurosciences. Thus, a journal focused on molecular cytogenetics is not limited to technical issues but will also address advances in current biomedical research. Molecular Cytogenetics will provide multilateral coverage of numerous applied and basic aspects of current biomedicine.Taking into account the growing amount of biomedical journals available, one can argue whether we need another one. However, any scientist working on theoretical and practical aspects of chromosome biology would undoubtedly agree that there are few journals covering this area of biology, and that there are no journals providing immediate open access. We performed an informal analysis (Figure 1) that shows the consistent interest of researchers to publish their original molecular cytogenetic data in peer-reviewed journals. However, to read
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