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Founder mutation in Parkinson's disease presented on 12/10/08


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Based on paper by Nuytemans, K. & et. al. from European Journal of Human Genetics 16: 471-479.

Published in: Technology, Health & Medicine
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Founder mutation in Parkinson's disease presented on 12/10/08

  1. 1. Founder mutation p.R1441C in the leucine-rich repeat kinase 2 gene in Belgian Parkinson’s disease patients Presented by: Pearl Pfiester 12.10.08
  2. 2. LRRK2 Gene <ul><li>LRRK2 = leucine-rich repeat kinase 2 gene </li></ul><ul><li>Contains two domains: Roc and Kinase </li></ul><ul><ul><li>Gene location: 12q12 </li></ul></ul>
  3. 3. Why study LRRK2 Gene? <ul><li>To date, six genes identified contribute to hereditary Parkinson’s Disease (PD) </li></ul><ul><li>Mutations in LRRK2 reported in 5% familial patients and 1-2% of sporadic mutations globally </li></ul><ul><ul><li>22 putative pathogenic mutations identified </li></ul></ul><ul><ul><li>2 nd most common pathogenic mutation: p.R1441C </li></ul></ul><ul><ul><li>Functional assays show increased levels of kinase activity in vitro for LRRK2 mutations </li></ul></ul>
  4. 4. Objective <ul><li>Identify mutations and prevalence in LRRK2 linked to Parkinson’s disease in Belgian patients with similar phenotypes </li></ul>
  5. 5. Signal Transduction <ul><li>Ligand binds to receptor </li></ul><ul><li>G protein dissociates from receptor </li></ul><ul><li>One G protein subunit activates adenylate cyclase that converts ATP to cAMP </li></ul><ul><li>cAMP activates PKA (protein kinase A) to phosphorylate proteins </li></ul>
  6. 6. Subjects <ul><li>304 Belgian PD patients that were residents of Flanders </li></ul><ul><li>18.1% had positive family history </li></ul><ul><li>Control group: 278 Belgiums with no clinical evidence of PD </li></ul>
  7. 7. Gene Sequencing <ul><li>PCR Amplified: 10 exons of Roc and Kinase domains of LRRK2 </li></ul><ul><ul><li>exons 29-31 and 38-44 </li></ul></ul><ul><li>Amplified strands were purified, sequenced, and analyzed by the ABI3730 DNA Analyzer technology </li></ul><ul><ul><li>The novel variants were confirmed and tested in the control group by pyrosequencing </li></ul></ul><ul><li>Using the UCSC Genome Browser, conserved evolutionary sequences can be compared between organisms </li></ul><ul><li>The effect of mutations at the protein level was predicted using the SIFT program </li></ul>
  8. 8. Haplotype Analysis <ul><li>28 LRRK2 intragenic and flanking markers were genotyped </li></ul><ul><li>The markers were analyzed in the control group to determine the frequency of the haplotype </li></ul><ul><li>The microsatellite markers were fluorescently labeled by PCR Amplification and then analyzed </li></ul>
  9. 9. Results <ul><li>The amplified exons in LRRK2 found 10 heterozygous carriers in the Belgian PD patients </li></ul><ul><ul><li>All had positive family history of PD </li></ul></ul><ul><ul><li>Frequency for heterozygous mutations in LRRK2 is 3.29% </li></ul></ul><ul><li>Only 6 patients out of the 10 carriers had the same mutation of p.R1441C so the frequency is 1.97% </li></ul><ul><li>The other 4 patients had novel missense mutations </li></ul><ul><li>The authors confirmed frequencies of five known SNPs from another European study </li></ul>
  10. 10. Results Reported and novel coding mutations in the LRRK2 Roc and kinase domains. Symbols: red stars = putative pathogenic missense mutations detected in the Flanders-Belgian PD population (6 out of 10 carriers) green stars = novel rare variants (4 out of 10 carriers) yellow stars = known polymorphisms
  11. 11. Data on protein conservation of all coding mutations in the LRRK2 Roc and kinase domains
  12. 12. Results for p.R1441C <ul><li>Of the 6 carriers with p.R1441C mutation, 5 had common tremor as initial onset </li></ul><ul><li>The other carrier had rigidity </li></ul>
  13. 13. Results <ul><li>10 Carriers found total </li></ul><ul><ul><li>6 had same mutation of p.R1441C </li></ul></ul><ul><ul><li>4 had novel missense mutation </li></ul></ul>
  14. 14. Results for p.R1441C <ul><li>Based on the markers in families DR75, DR99, and DR135, the authors were able to find a disease haplotype </li></ul><ul><ul><li>Probands in the other 3 families all shared alleles for several markers within the inferred disease haplotype </li></ul></ul><ul><ul><ul><li>So the haplotype was supported </li></ul></ul></ul><ul><li>Combining allele and haplotype data, a shared segment of 438 kb between centromeric D12S2194 and telomeric D12S1301 was found </li></ul><ul><ul><li>This shared haplotype was not present in the control group </li></ul></ul>
  15. 15. Results for p.R1441C
  16. 16. Results: Allele and Haplotype Analysis for p.R1441C
  17. 17. Results for Novel Mutations
  18. 18. Results for Novel Mutations
  19. 19. Conclusion <ul><li>Found 5 mutations in 10 carrier patients: R1441C, Y2189C, R1325Q, K1468E, and R1483Q </li></ul><ul><li>The estimated frequency for overall LRRK2 mutations is 3.29%. </li></ul><ul><li>p.R1441C mutation was present on one disease haplotype </li></ul><ul><ul><li>Supports founder effects involved </li></ul></ul><ul><ul><li>Comparisons between Italian patients showed independence </li></ul></ul><ul><ul><ul><li>Particular codon must be a hotspot because three other mutated codons have been reported. </li></ul></ul></ul><ul><li>Phenotypes: 5 had tremor whereas the other patient experienced rigidity </li></ul><ul><ul><li>Not all genetic studies reported detailed phenotypes </li></ul></ul><ul><ul><li>Low penetrance </li></ul></ul><ul><ul><li>Are the 4 novel missense mutations pathogenic or benign polymorphisms? </li></ul></ul><ul><li>Need functional assays to understand mutation’s role for disease and to determine more accurate frequencies for benign and pathogenic polymorphisms in LRRK2 </li></ul><ul><li>In conclusion, 5 missense mutations were found where 4 were novel in important conserved regions. This paper showed that p.R1441C is a frequent cause in the Flanders region of Belgium. </li></ul><ul><ul><li>Pathogenicity and function of the gene and mutations is yet to be determined. </li></ul></ul>