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Chromosomal architecture following Centromere Dysfunction in Fission Yeast
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| Dhaka 24th Aug, ’08. In a report published in the 22nd Aug. ‘08 issue of Science, Ishii et al. at Kurume-, Osaka- and the National Institute of Information and Communications Technology, Japan reported the role of heterochromatin in chromosome reorganization after centromere dysfunction in fission yeast (Schizosaccharomyces pombe). It is a well established phenomenon that in Eukaryotes, centromeres are essential for equal chromosome separation during the mitotic metaphase phase of cell division. However, little was known regarding the manner in which centromere dysfunction affects the chromosomal architecture. Ishii et al. showed that the conditional deletion of the centromere produces survivors carrying either a neo-centromere-acquired chromosome at the subtelomeric region or an acentric chromosome rescued by inter-telomere fusion with either of the remaining chromosomes. The group has also identified the role of RNAi in neo-centromere formation: the ratio between newly formed neocentromere and those fused to the telomeres is considerably reduced by the inactivation of genes due to the formation of RNAi–dependent heterochromatin. Summarized by Mahdi Moosa, Genetic Engg. and Biotech, DU.
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| Posted on:
9/3/20088:46:31 AM
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Crystal Structure of a Sodium Galactose Transporter (vSGLT) opens a new horizon in drug designing
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| Dhaka 11th Aug. ’08. In a research article published online in Science in its 8th August issue Faham et al. report the crystal structure of Sodium/Galactose symporter of Vibrio parahaemolyticus, vSGLT. Sodium glucose symporters play an important physiological role. These transmembrane symporters are present in the intestinal lumen, where they transport galactose using the energy of thermodynamically downhill sodium symport. The study of these symporters has revealed in-depth insights into a large family of transmembrane proteins, namely, Sodium Solute Symporters (SSS). SSSs cotransport Na+ with sugars, amino acids, inorganic ions, or vitamins, thereby playing a vital role in the pathology of various human diseases such as diabetes, congenital metabolic disorders of glucosegalactose malabsorption (GGM) and idide transport defect (ITD). Conformational knowledge of this symporter will pave the way of designing novel drugs targeting the SSS’s, which share similar structures with vSGLT. Summarized by Mahdi Moosa, Dept. of Genetic Engg. & Biotechnology, DU.
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| Posted on:
9/3/20088:45:42 AM
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Correcting b-thalassaemia through Lentivirus-mediated Gene Therapy
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| Dhaka 05th August, ’08. b--thalassaemia is one of the major inherited haemoglobinopathies. This disease is caused by mutations in the gene b-globin. In a research article published 29th July edition of PNAS, Miccio et al. report a method of long term correction of b-thalassaemia through lentivirus-mediated gene delivery. Effective gene therapy for b-thalassaemia requires stable transfer of a functional b-globin gene into hematopoietic stem cells and its high and regulated hemoglobin expression in the erythroblastic progeny. The authors have developed an erythroid specific lentiviral vector delivered expression system of b-globin gene from a minimal promoter/enhancer element containing two hypersensitive sites from the b-globin locus control region. Transplantation of transduced HSCs into thalaessemic mice led to a stable and long-term correction of anemia with all the red blood cells expressing the transgene. Summarized by Mahdi Moosa, Genetic Engg. & Biotech, DU.
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| Posted on:
9/3/20088:45:12 AM
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Hair follicles of mammalian skin: Mechanism of adult stem cell morphogenesis
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| Dhaka 17th July, 2008. In an article published July 2008 in Cell Stem Cell, Nowak et al. report the mechanism of stem cell development and morphogenesis in the early stages of growth of mammalian skin. Adult stem cells (SCs), present in specific niches, maintain tissues during normal homeostasis and wound repair. The origin and the organizational pattern of adult SCs within a niche remains largely unknown. The study of the above authors unveils that the progeny of Sox9-expressing cells develop into adult SCs in earliest stages of hair follicle morphogenesis. Furthermore, they have shown that early SCs can contribute to all skin epithelial lineages; and in their absence, the normal morphogenesis of HFs and SCs is blocked, severely compromising epidermal wound repair process. Summarized by Mahdi Moosa, Genetic Engineering & Biotechnology, DU
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| Posted on:
8/20/200811:20:05 AM
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Increasing the efficiency of RNAi (RNA interference) mediated knockdown
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| Dhaka 13th July, 2008. In a research article published in 8th July issue of PNAS (USA), Diederichs et al. report an novel method of increasing efficiency of RNAi mediated knockdown. One of the major problems with using RNAi is its variable efficiency and specificity. This complicates studies targeting individual genes and significantly impairs large-scale screens using genome-wide knockdown libraries. Diederichs et al. have shown that co-expression of Argonaute-2 protein along with interfering RNA gives uniform and highly specific target gene suppression. This observation has immediate applications for optimal design of RNAi strategies.Please click here for the article. Summarized by Mahdi Moosa, Genetic Engineering & Biotechnology, DU.
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| Posted on:
8/20/200811:19:22 AM
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Lateral Gene Transfer in Eukaryotes
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| Dhaka 13th July, ’08. In a research article published online 9th July in PLoS ONE, Graham et el. report the event of Lateral Gene Transfer (LGT) in Eukaryotes. LGT has been a well-documented event in bacteria and viruses, but thus far this phenomenon has not been recorded in Eukaryotes. Here, Graham et al. provide the first such evidence for LGT in vertebrates. Fishes living in cold water produce an endogenous antifreeze protein encoded by a specific gene. The endogenous antifreeze protein allows fishes of different taxa to survive in cold water such as in the arctic ocean.. Until now, scientists believed that that these AFP proteins have evolved independently in different phylogenetic lineages, while some underwent convergent evolution. The isolated occurrence of three very similar type II AFPs in three distantly related fish species (herring, smelt and sea raven) cannot explain this unique event to be independent of one another. The study of Graham et al. suggests LGT to be the possible mechanism accounting for the origin of the type two AFPs in the three different fish species that were investigated by these authors.Please click here for the article. Summarized by Mahdi Moosa, Genetic Engineering & Biotechnology, DU.
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| Posted on:
8/20/200811:19:06 AM
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Integrative genome analysis of somatic cell reporgramming
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| Dhaka 10th July, 2008. In a research article published online 3rd July edition of Nature, Mikkelsen et al. report integrative genome analysis of somatic cell reprogramming. The generation of induced pluripotent stem (iPS) cells from the somatic tissue is a fascinating avenue of current research due to its immense therapeutic potential. Ectopic expression of certain transcription factors can re-programme somatic cells into pluripotent state albeit at low efficiency. The mechanism and nature of molecular changes underlying the process of direct reprogramming was hitherto mostly unknown. To address this issue Mikkelsen et al. carried out integrative genomic analysis of reprogramming of mouse fibroblasts and B lymphocytes. Their study reveals the underlying reasons behind the low efficiency of direct reprogramming. Besides their study also demonstrates that RNA inhibition of some other transcription factors can facilitate reprogramming and treatment with DNA methyltransferase inhibitors can improve the overall efficiency of the reprogramming process. Summarized by Mahdi Moosa, Genetic Engg. & Biotechnology, DU.
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| Posted on:
8/20/200811:18:28 AM
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Excision of selectable marker gene from transgenic tobacco using the GM-gene-deletor system regulated by a heat-inducible promoter
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| Dhaka July 1, 2008. The success of transgenic plant development depends largely on selection of transformed over non-transformed cells and tissues, and finally regeneration from there. For this selection various selectable marker genes are used which either give selection in presence of selective chemical agents (antibiotics and herbicides) or give visual characteristics like shooty phenotype (conferred by isopentenyl transferase gene (ipt) from Agrobacterium tumefaciens). Selectable marker genes conferring resistance to chemicals have concerns on biosafety issues, while phenotypic characters give abnormal morphology of no agronomic importance. Such a situation has
prompted molecular breeders to remove the marker gene from the transgenics. In an article published online on the 15 March 2008 edition of Biotechnol Lett (DOI 10.1007/s10529-008-9684-7), Lue et. al. report a technology comprising excision of selectable marker genes based on a ‘genetically modified (GM)-gene-deletor’ system. They constructed a new binary vector where T-DNA was flanked by two loxP/FRT fusion sequences as site-specific recombination sites.The article reports a dependable strategy for auto-excising of selectable marker gene(s) to produce marker-free transgenic plants. To read the full summary please click here. The whole article is available only for GNOBB users here. ~Summarized by Dr. Aparna Islam, Biotechnology Programme, BRAC University..
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| Posted on:
8/3/20081:18:03 AM
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Analysis of Branchiostoma floridae genome sheds light on the vertebrate origin
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| Dhaka July 5, 2008. In a paper published in the 1st July issue of Genome Research,
Holland et al. explore the evolution of cephalochordates from
last common ancestor of the chordates (LCAC).
Chordate evolution has been a matter of intense debate
among the biologists for the past one century. This
phylum comprises cephalochordates (amphioxus or lancelets), urochordates
(tunicates), and vertebrates. According to Gaskell’s view,
cephalocordates lost their skeleton and cranial region after their
divergence from urochordate and vertebrate lineage. Others considered that
cephalocordates diverged before the origin of vertebrates. Comparative whole
genome analysis of the cephalochordate B. floridae
with several other chordate genomes by Holland et al. supports the
latter view. In this paper, Holland et al. also
address the evolution of homeobox genes, the neural crest
gene network, opsins, endocrine genes, immune systems, and transcriptional
enhancers of B. floridae. Their analysis shows that amphioxus
reflects the primitive prevertebrate condition. Nevertheless, it also
exhibits uniquely specialized features that arose in the half a billion
years after its divergence from the rest of the chordate lineage
Summarized by Mahdi Moosa
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| Posted on:
8/3/200812:58:27 AM
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Evolution of a novel sex determination gene in Honeybee (Apis mellifera)
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| Dhaka July 1, 2008. In an article published online on the 25th June edition of Nature,
Hasselmann et al. report a new sex determination gene of honeybee (Apis
mellifera), namely, fem. Honeybee genome was published in
2006. But the later identification of this gene is partly
attributable to highly AT-rich Sex Determining Loci (SDL) and
underrepresented in various cloning and shot-gun sequencing strategies.
fem gene is located 12 kb upstream of already known complementary
sex determiner (csd) gene and shares >70% similarity with Csd protein at
amino acid level. RNA interference induced knock-out experiments
indicate that fem is the second binary switch gene of the sex
determination pathway that, when active, regulates the entire
developmental program of females but not that of males. Comparative
analysis of fem and csd coding sequences from five bee species
indicates a recent origin of csd in the honeybee lineage from the fem
progenitor and provides evidence for positive selection at csd
accompanied by purifying selection at fem. The fem locus
in bees uncovers gene duplication and positive selection as evolutionary
mechanisms underlying the origin of a novel sex determination pathway.
Summarized by Mahdi
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| Posted on:
8/3/200812:56:29 AM
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