6 results on '"Thomas, NS"'
Search Results
2. A functional assay for microRNA target identification and validation.
- Author
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Gäken J, Mohamedali AM, Jiang J, Malik F, Stangl D, Smith AE, Chronis C, Kulasekararaj AG, Thomas NS, Farzaneh F, Tavassoli M, and Mufti GJ
- Subjects
- 3' Untranslated Regions, Cell Line, Cloning, Molecular, Down-Regulation, Ganciclovir pharmacology, Gene Expression Regulation, Gene Knockdown Techniques, Gene Library, Humans, MicroRNAs chemistry, Transfection, MicroRNAs metabolism
- Abstract
MicroRNAs (miRNA) are a class of small RNA molecules that regulate numerous critical cellular processes and bind to partially complementary sequences resulting in down-regulation of their target genes. Due to the incomplete homology of the miRNA to its target site identification of miRNA target genes is difficult and currently based on computational algorithms predicting large numbers of potential targets for a given miRNA. To enable the identification of biologically relevant miRNA targets, we describe a novel functional assay based on a 3'-UTR-enriched library and a positive/negative selection strategy. As proof of principle we have used mir-130a and its validated target MAFB to test this strategy. Identification of MAFB and five additional targets and their subsequent confirmation as mir-130a targets by western blot analysis and knockdown experiments validates this strategy for the functional identification of miRNA targets.
- Published
- 2012
- Full Text
- View/download PDF
3. Cyclin D2 controls B cell progenitor numbers.
- Author
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Mohamedali A, Soeiro I, Lea NC, Glassford J, Banerji L, Mufti GJ, Lam EW, and Thomas NS
- Subjects
- Animals, Antigens, CD19 metabolism, Antigens, Differentiation metabolism, B-Lymphocytes drug effects, Blotting, Western, Bone Marrow metabolism, CD5 Antigens analysis, CD5 Antigens metabolism, Cell Count, Cells, Cultured, Colony-Forming Units Assay, Cyclin D2, Cyclin D3, Cyclins metabolism, Mice, Mice, Inbred C57BL, Mice, Knockout, Oncogene Proteins metabolism, Phosphorylation, Proto-Oncogene Proteins c-bcr, Retinoblastoma Protein metabolism, Signal Transduction, B-Lymphocytes cytology, Cyclins physiology, Hematopoietic Stem Cells cytology, Protein-Tyrosine Kinases, Proto-Oncogene Proteins
- Abstract
Cyclin D2 affects B cell proliferation and differentiation in vivo. It is rate-limiting for B cell receptor (BCR)-dependent proliferation of B cells, and cyclin D2-/- mice lack CD5+(B1) B lymphocytes. We show here that the bone marrow (BM) of cyclin D2-/- mice contains half the numbers of Sca1+B220+ B cell progenitors but normal levels of Sca1+ progenitor cells of other lineages. In addition, clonal analysis of BM from the cyclin D2-/- and cyclin D2+/+ mice confirmed that there were fewer B cell progenitors (B220+) in the cyclin D2-/- mice. In addition, the colonies from cyclin D2-/- mice were less mature (CD19lo) than those from cyclin D2+/+ mice (CD19Hi). The number of mature B2 B cells in vivo is the same in cyclin D2-/- and cyclin D2+/+ animals. Lack of cyclin D2 protein may be compensated by cyclin D3, as cyclin-dependent kinase (cdk)6 coimmunoprecipitates with cyclin D3 but not cyclin D1 from BM mononuclear cells of cyclin D2-/- mice. It is active, as endogenous retinoblastoma protein is phosphorylated at the cdk6/4-cyclin D-specific sites, S807/811. We conclude that cyclin D2 is rate-limiting for the production of B lymphoid progenitor cells whose proliferation does not depend on BCR signaling.
- Published
- 2003
- Full Text
- View/download PDF
4. Dosage-sensitive X-linked locus influences the development of amygdala and orbitofrontal cortex, and fear recognition in humans.
- Author
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Good CD, Lawrence K, Thomas NS, Price CJ, Ashburner J, Friston KJ, Frackowiak RS, Oreland L, and Skuse DH
- Subjects
- Adolescent, Adult, Child, Chromosome Mapping methods, Chromosomes, Human, X genetics, Female, Gene Deletion, Gene Dosage, Genetic Diseases, X-Linked physiopathology, Genetic Diseases, X-Linked psychology, Humans, Intelligence, Karyotyping, Magnetic Resonance Imaging methods, Male, Middle Aged, Neuropsychological Tests, Pattern Recognition, Visual, Turner Syndrome genetics, Turner Syndrome physiopathology, Turner Syndrome psychology, Amygdala growth & development, Facial Expression, Fear, Frontal Lobe growth & development, Genetic Diseases, X-Linked genetics
- Abstract
The amygdala, which plays a critical role in emotional learning and social cognition, is structurally and functionally sexually dimorphic in humans. We used magnetic neuroimaging and molecular genetic analyses with healthy subjects and patients possessing X-chromosome anomalies to find dosage-sensitive genes that might influence amygdala development. If such X-linked genes lacked a homologue on the Y-chromosome they would be expressed in one copy in normal 46,XY males and two copies in normal 46,XX females. We showed by means of magnetic neuroimaging that 46,XY males possess significantly increased amygdala volumes relative to normal 46,XX females. However, females with Turner syndrome (45,X) have even larger amygdalae than 46,XY males. This finding implies that haploinsufficiency for one or more X-linked genes influences amygdala development irrespective of a direct or indirect (endocrinological) mechanism involving the Y-chromosome. 45,X females also have increased grey matter volume in the orbitofrontal cortex bilaterally, close to a region implicated in emotional learning. They are as poor as patients with bilateral amygdalectomies in the recognition of fear from facial expressions. We attempted to localize the gene(s) responsible for these deficits in X-monosomy by means of a deletion mapping strategy. We studied female patients possessing structural X-anomalies of the short arm. A genetic locus (no greater than 4.96 Mb in size) at Xp11.3 appears to play a key role in amygdala and orbitofrontal structural and (by implication) functional development. Females with partial X-chromosome deletions, in whom this critical locus is deleted, have normal intelligence. Their fear recognition is as poor as that of 45,X females and their amygdalae are correspondingly enlarged. This 4.96 Mb region contains, among others, the genes for monoamine oxidase A (MAOA) and B (MAOB), which are involved in the oxidative deamination of several neurotransmitters, including dopamine and serotonin. Abnormal activity of these neurotransmitters has been implicated in the aetiology of several neurodevelopmental disorders in which social cognitive deficits are prominent. These associated deficits include a specific lack of fear recognition from facial expressions. We show that the thrombocytic activity of MAOB is proportionate to the number of X-chromosomes, and hypothesize that haploinsufficiency of this enzyme in 45,X females predisposes to their deficits in social cognition.
- Published
- 2003
- Full Text
- View/download PDF
5. Ontogeny of human fetal testicular apoptosis during first, second, and third trimesters of pregnancy.
- Author
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Helal MA, Mehmet H, Thomas NS, Cox PM, Ralph DJ, Bajoria R, and Chatterjee R
- Subjects
- Female, Fetus physiology, Gestational Age, Humans, Leydig Cells physiology, Male, Pregnancy Trimester, First, Pregnancy Trimester, Second, Pregnancy Trimester, Third, Reference Values, Sertoli Cells physiology, Spermatozoa physiology, Apoptosis physiology, Pregnancy physiology, Testis embryology
- Abstract
During spermatogenesis in human adults, testicular germ cells proliferate, differentiate, and die by apoptosis. However, little is known about the temporal or spatial nature of this programmed cell death. Such information may be useful for understanding prenatal developmental biology as well as spermatogenesis during adulthood, particularly in the context of germ cell disorders. We undertook this study to determine 1) whether apoptosis occurred in a cell-specific fashion in the germ cell population and the supporting somatic cells; and 2) whether apoptosis varied with gestational age. We examined human fetal testicular tissues obtained from 17 karyotypically and structurally normal fetuses of mothers who underwent spontaneous or induced abortions. Three gestational ages were defined as follows: group A, 12-13 wk gestation (n = 5); group B, 20-22 wk gestation (n = 7); and group C, 37-40 wk gestation (n = 5). Morphology in conjunction with in situ end labeling was used to identify and quantify apoptotic nuclei in fetal gonadal tissues. The results of this study suggest that gonadal apoptosis occurred in germ cells, Sertoli cells, and Leydig cells at all gestational ages. Apoptotic death was highest in the Leydig cells, followed by germ cells and Sertoli cells. There was a significant positive correlation between the apoptosis of germ cells and Sertoli cells (P < 0.01) and a negative correlation between healthy germ cells and Sertoli cells (P < 0.001). There was also a negative correlation between the intratubular cell number and the gestational age. Specifically, the proportion of Sertoli cells decreased with gestational age, although there was no significant change in the germ cell in relation to gestational age. No such relationship was found in the Leydig cell population, all of which reside outside the seminiferous tubules. These results are the first to suggest that fetal testicular apoptosis begins in the first trimester, occurs in the three major cell types, and continues throughout pregnancy. Our data also suggest that in the fetal gonad, germ and Sertoli cell proliferation and death may be controlled by a genetic program distinct from that of the Leydig cells. This information is relevant to the understanding of abnormal spermatogenesis associated with infertility and to germ cell tumors in adult life.
- Published
- 2002
- Full Text
- View/download PDF
6. Polyribosome binding of rabbit globin messenger RNA and messenger ribonucleoprotein labelled with bacteriophage-T4 RNA ligase and 5'-[32P] phosphocytidine 3'-phosphate.
- Author
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Thomas NS, Butcher PD, and Arnstein HR
- Subjects
- Animals, Protein Biosynthesis, Rabbits, Reticulocytes metabolism, Cytidine Diphosphate metabolism, Cytosine Nucleotides metabolism, Globins genetics, Nucleoproteins genetics, Polynucleotide Ligases metabolism, Polyribosomes metabolism, RNA Ligase (ATP) metabolism, RNA, Messenger genetics, Ribonucleoproteins genetics, T-Phages enzymology
- Abstract
Rabbit polyribosomal globin messenger RNA (mRNA) and messenger ribonucleoprotein (mRNP) were labelled at the 3' poly(A) tail to high specific activity with T4 RNA ligase and [5'-(32)P]pCp without consequent loss of functional activity. Labelled message was translated in both micrococcal nuclease treated and untreated rabbit reticulocyte lysates, as shown by the formation of labelled polyribosomes. The utilisation of labelled messenger was abolished by T2 toxin or sodium fluoride which are known to inhibit protein synthesis.Images
- Published
- 1983
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