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Somatic hypermutation
 

Somatic hypermutation

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desh bandhu presentation......

desh bandhu presentation......

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    Somatic hypermutation Somatic hypermutation Presentation Transcript

    • SOMATIC HYPERMUTATIONSOMATIC HYPERMUTATIONDeshBandhu 10/pbt/006
    • Contents
      1-Introduction
      2-Molecules involve in SHM
      3-Model of SHM
      4-Future Directions
    • Introduction
      somatic hypermutation (SHM) is a diversity generating, regulated cellular mechanism displayed by the adaptive immune response.
      Somatic Hypermutation adds diversity in already Rearranged Gene Segments.
      Somatic hypermutation occurs at a frequency of
      10¯3/base pair/ generation, than the spontaneous mutation rate about 10⁻8/bp/generation.
    • This Rate is higher hence the name, hypermutation.
      These mutations occur mostly at “hotspots” in the DNA, known as hypervariable regions.
      These regions correspond to the complementarity determining regions, the sites involved in antigen recognition on the antibody.
    • These mutation result from nucleotide substitution rather than addition or deletion.
      They influence the process of affinity maturation of B cells.
      Affinity maturation leads to increase the affinity of antibodies for a particular antigen.
    • Molecules involved in SHM
      IgM antibodies expressing V regions that have undergone SHM, as well as IgG and IgA antibodies with no somatic mutations.
      Activation-induced cytidinedeaminase: A
      B cell-specific protein required for SHM.
      Uracil N-glycosylase: Removing uracil generated by AID deamination.
    • Mismatch repair proteins: Mismatch repair (MMR) normally maintains genomic integrity.
      MMR eliminates mutations that arise spontaneously in the genome.
      Error-prone DNA polymerases: increase mutation rate.
    • Model of somatic hypermutation
    • Future directions
      • Evolving protein in mammalian cell using SHM
      SHM cell with the target gene integrated in the genome
      cell population with the target gene mutated
      cells with the desired phenotype
      amplified cells with the desired phenotype
      isolate and characterize
    • SHM Plateform
    • To Produce New Fluorescent Proteins
      Tsien’s group has cloned a red fluorescent protein (RFP) into human B-cells and allowed them to make variants that could then be isolated based on their colors by flow-cytometry.
    • Questions??