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Archive - Feb 7, 2014

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Giant Protein on Mutant Staph aureus Surface Hinders Clumping and Reduces Ability to Cause Disease

A genetic mechanism that controls the production of a large spike-like protein (the Giant Staphylococcal Surface Protein [GSSP])on the surface of Staphylococcus aureus(staph) bacteria alters the ability of the bacteria to form clumps and to cause disease, according to a new University of Iowa (UI) study. The new study is the first to link this genetic mechanism to the production of the giant surface protein and to clumping behavior in bacteria. It is also the first time that clumping behavior has been associated with endocarditis, a serious infection of heart valves that kills 20,000 Americans each year. The findings were published in the December 2103 issue of the open-access journal PLOS Pathogens. Under normal conditions, staph bacteria interact with proteins in human blood to form aggregates, or clumps. This clumping behavior has been associated with pathogenesis -- the ability of bacteria to cause disease. However, the mechanisms that control clumping are not well understood. In the process of investigating how staph bacteria regulate cell-to-cell interactions, researchers at the UI Carver College of Medicine discovered a mutant strain of staph that does not clump at all in the presence of blood proteins. Further investigation revealed that the clumping defect is due to disruption of a genetic signaling mechanism used by bacteria to sense and respond to their environment. The study shows that when the mechanism is disrupted, the giant surface protein is overproduced -- giving the cells a spiny, or "porcupine-like" appearance -- and the bacteria lose their ability to form clumps.

Rett Syndrome Genetic Variants Now Available for Advance Testing, Diagnosis, and Research

Despite the identification of gene mutations in methyl CpG binding protein 2 (MECP2) being linked to Rett syndrome (RS), research has been hindered by the lack of commercially available reference materials. Through collaboration between the Centers for Disease Control and Prevention (CDC) and members of the clinical-laboratory and non-profit–research communities, 35 DNA samples containing many common RS genetic variants have now been characterized and made publicly available, eliminating a major stumbling-block for investigators and opening the possibility of earlier, more accurate diagnosis of Rett syndrome, reports The Journal of Molecular Diagnostics. The study was conducted via the CDC Genetic Testing Reference Materials Coordination Program (GeT-RM), which aims to help the genetic testing community obtain appropriate and well-defined reference materials for inherited genetic disorders, including cancer and infectious diseases. Researchers selected eight cell lines from RS patients already available from the National Institute of General Medical Sciences' Coriell Cell Repository, which contained six of the most common mutations that cause RS, as well as one additional point mutation. In addition, DNA was obtained from 27 newly established cell lines derived from blood samples from Rett patients, which included a number of other MECP2 variants. Two of the samples were from males. The samples were sent for DNA sequence and deletion/duplication analyses (using MLPA, semi-quantitative PCR, or array) to College of American Pathologist–accredited clinical genetic testing laboratories, and each sample was tested in between two to five laboratories. The investigators found that the results were concordant among laboratories and assay platforms.