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| Tuesday, February 7, 2012
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12:30 PM - 1:30 PM
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| Wednesday, February 8, 2012
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11:30 AM - 1:00 PM
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Bioinformatics Seminar Series:CRISPR, adaptive immunity system in Archaea and Bacteria: Lamarckian evolution and a general model of evolution of environmental sensors
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| Description: |
Eugene V. Koonin, NIH/NLM/NCBI
TOC LAB Stata Center Building 32-Room G575.
The CRISPR-Cas adaptive immunity system is present in nearly all Archaea and about half of Bacteria. This system consists of arrays of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and suits of CRISPR-Associated (cas) genes; the CRISPR cassettes contains unique spacers about 40 basepairs in length within each repeat unit. Some of the spacers are identical to fragments of viral or plasmid genes. It has been shown that Cas proteins provide enzymatic activities that are required for utilization of the spacer transcripts as guide RNAs to cleave and inactivate the cognate alien DNA and in some cases possibly mRNA. The CRISPR-Cas systems are encoded by operons that have extraordinarily diverse architectures and a high rate of evolution of both the cas genes and the unique spacer content. Three complementary approaches to the study of CRISPR evolution will be presented. First, comprehensive analysis of the sequences and structures of Cas proteins using the most sensitive methods of computational analysis yielded a simple scenario for the origin and evolution of the CRISPR-Cas systems that implies the origin of prokaryotic adaptive immunity in thermophilic Archaea. Second, a comprehensive analysis of the selection processes that act on cas genes revealed a gradient from moderate to extremely weak purifying selection across the cas gene suite. Third, a mathematical model based on a cost-benefit analysis of the CRISPR-Cas system in the course of its coevolution with viromes of varying diversity was developed. Exploration of the parameter space of this model shows that selection prevents the loss of the CRISPR-Cas system within an interval of moderate viral diversity. At both very low and very high viral diversity, CRISPR-Cas systems become practically useless for bacteria and archaea, and are lost due to their intrinsic cost. This model has more general applications for the evolution of various environmental sensors. The CRISPR-Cas systems that incorporate new information into a genome in response to environmental cues seem to present a case of bona fide Lamarckian evolution.
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Patrice Macaluso
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| Thursday, February 9, 2012
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Noon - 1:00 PM
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Alveolar Augmentation and Implant Osseointegration: GBR, Bone Biomaterials, and Biologics
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| Description: |
Speaker: Ulf ME Wikesjö, DDS, DMD, PhD, Georgia Health Sciences University College of Dental Medicine
Location: The Forsyth Institute, Seminar Room A, 245 First St., 17th Fl., Cambridge
Abstract: Surgical placement of oral implants is governed by the prosthetic design and by the morphology and quality of the alveolar bone. Often, implant placement may be difficult, if at all possible, due to alveolar ridge aberrations. In consequence, prosthetically dictated implant positioning commonly entails bone augmentation procedures. One objective of our laboratory is to evaluate the biologic potential of bone morphogenetic proteins (BMPs) including rhBMP-2, rhOP-1/rhBMP-7, rhGDF-5/rhCDMP-1, and other candidate biologics including PTH, osteoactivin, platelet-rich-plasma (PRP), and bone biomaterials and devices for alveolar ridge augmentation/implant fixation using discriminating, critical-size, clinically relevant supraalveolar defect models, peri-implantitis defect models and maxillary sinus models and canine, porcine and nonhuman primate platforms to explore their clinical potential. Critical-size rodent models are used for screening purposes of candidate biologics and biomaterials/scaffolds. This presentation will discuss the unique biologic potential, the clinical relevance and perspectives of recent and unpublished observations of BMP technologies for alveolar bone augmentation and oral implant fixation, in particular the development of a unique bone-inductive oral implant, BMP dosing and delivery strategies. This presentation will also address merits and explain short-comings of current treatment protocol including bone biomaterials, guided bone regeneration (GBR), and BMPs. Our studies suggest that BMPs have an unparalleled, dose dependent potential to augment alveolar bone and support implant osseointegration and long-term functional loading. Inclusion of BMPs for alveolar augmentation and osseointegration will not only enhance predictability of existing clinical protocol but radically change current treatment paradigms. Inclusion of the bone-inductive oral implant in the treatment panorama may make “grafting” and GBR procedures altogether obsolete.
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| Contact: |
Pam Quattrocchi
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4:00 PM - 5:00 PM
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5:30 PM - 7:00 PM
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Week of Sunday, February 5, 2012
