An Sci 362 1st Edition Lecture 24 Outline of Last Lecture I. What are structural variantsII. Significance of structural variants vs. other polymorphismsIII. How are structural variants detectedIV. How do structural variants cause aberrant phenotypesOutline of Current Lecture I. Some definitionsII. What is bovine spongiform encephalopathy (BSE)?a. Causative agentb. Symptomsc. TransmissionIII. BSE and vCJDIV. Genetic variation in the bovine prion proteinV. Testing for BSE and preventionCurrent LectureDefinitions for Some Potentially Unfamiliar Terms- Iatrogenic: adverse condition in a patient resulting from treatment by a physician- Myoclonus: shock-like contractions of a muscle or group of muscles- Paresthesia: an abnormal sensation, as burning, prickling- Dysethesia: a painful, persistent sensation induced by a gentle touch of the skin- Ataxia: failure of muscular coordinationWhat is BSE?- Progressive neural disordero ~ 5 year incubation period from infection to clinical signs- Epidemic occurred in UK, lesser incidence in continental Europe, Japan- Recent cases in Canada and US- Causative Agento Prion (abnormal form of a normal cellular protein)o Extremely resistant to heat, protease digestion- Clinical Signs/Symptomso Changes in temperament (nervousness, aggression)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.oo Abnormal postureo Incoordination and difficulty in standingo Decreased milk production in dairy cattleo Loss of body weight despite continued appetiteo Abnormally stilted gaito High steppingo Heightened sensory perceptiono Itchingo Anorexiao Excessive licking- Transmissiono Oral intake of PrPSC Outbreak in United Kingdom thought to result from feeding ruminant-derived meat and bone meal to cattleo Horizontal transmission? No evidence of transmission from infected to susceptible cattle in close contact or through contaminated pasture Johnson et al. (2007) PLoS Pathology 3(7):874-881 Horizontal transmission of chronic wasting disease (TSE) in deer and elk ? Examined effect of binding prion with soil particles on transmissibility Prions bound to montmorillonite (common mineral particle in soil - clay) are:- Orally bioavailable- More transmissible and infectiveo Maternal Transmission Analysis of Dam-Calf Pairs of BSE Cases: Confirmation of a Maternal Risk Enhancement. Donnelly et al. 1997. Proceedings: Biological Sciences, Vol.264 (1388): 1647-1656 Calves born to dams within 24 months of onset of BSE or after onset of BSE in dam more likely to develop BSE (all calves born after ban on feeding meat and bone meal) Studies of embryo transfer from cattle clinically affected by BSE Veterinary Record 150:365-78 (2002) 167 BSE cows and 13 sires (8 with BSE) used to produce 587 viable embryos  Embryos transferred into non-BSE females, both recipients and resulting calves monitored for BSE for 7 years No clinical or histopathological evidence of BSE in anyBovine PrP Sequence Variation- Only one known change altering amino acid sequence- 5 or 6 copies of octapeptide repeat sequence- No apparent association between this change and susceptibility to BSE- Two insertion / deletion polymorphisms observed in PrP promoter regiono 12 bp indelo 23 bp indel- Tentative association with BSE observed in European Holstein, Simmental and Fleckvieh cattle breeds (ie. deletion allele frequency 2-4% greater in BSE cattle, P-value between 0.01 and 0.03)- No association in Brown Swiss breed- Cases of atypical BSE are likely to have PRNP haplotype OBSE testing program in USA- Test high-risk cattle:- Nonambulatory- Cattle exhibiting signs of a central nervous system disorder- Cattle exhibiting other signs that may be associated with BSE, such as emaciation or injury- Dead cattle- Random sampling from apparently normal, aged animals- Rapid screening test first (enzyme-linked immunosorbant assay, ELISA, brain material)o Sensitivity is a measure of a test’s ability to detect truly infected subjects (99.8%)o Specificity is a measure of as a test’s ability to correctly classify subjects as being uninfected in the absence of disease (>99.99%)- If result positive or inconclusive, follow-up with more testing to confirm (Western blot, immunohistochemistry)- If positive o Animal destroyed and carcass does not enter food chaino Attempt to identify other animals experiencing same feed exposure at young age- Cumulative total of tests since June 1, 2004 >1 million- Four positive animals identified to date (Washington, Texas, Alabama and California)- Ongoing surveillance program tests ~40,000 animals per yearBSE Prevention in USA- 1997 o FDA Feed Ban: prohibits mammalian protein in ruminant feed- 2008o FDA Feed Ban Enhancement: prohibits high-risk cattle material (brain and spinal cords) in all animal feed. Effective April 27, 2009; compliance date October 26, 2009Early Detection of Disease- Blood biomarkerso Protein associated with disease development not prion itselfo Found in blood, so sample easily obtained- Value of blood biomarkerso Earlier detection of diseaseo Rapid detection in live animal (vs. postmortem)- Proteins expressed in affected tissue  Subset unique to the disease of interest  Further subset found in blood at readily detectable levels  Further