immuno-VDJ recombination.pptx

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1. VDJ RECOMBINATION KUBRA BATOOL LAIQA SHAHID KHANSA TAHIR NABIHA KARAMAT

2. How does this diversity achieved in term of anti body production?? In a genetic recombination, which happens in anti body light chain and heavy chain, known as VDJ recombination. There are 51V , 27D, 6 J segments

3. VDJ RECOMBINATION V(D)J recombination  is the mechanism of somati c recombination  that occurs only in developing  lymphocyte  during the early stages of T and B cell maturation.

4. Key Enzymes and C omponents The process of V(D)J recombination is mediated by VDJ recombinase , which is a diverse collection of enzymes. The key enzymes involved are:   R ecombination activating genes 1 and 2 (RAG )   T erminal deoxynucleotidyl transferase  ( TdT ) Artemis  nuclease, a member of  non-homologous end joining (NHEJ) pathway for DNA repair  DNA-dependent protein kinase ( DNA-PK) X-ray repair cross-complementing protein 4 ( XRCC4) DNA ligase IV   N on-homologous end-joining factor 1 ( NHEJ1) DNA polymerases λ and μ .

5. Recombination Signal Sequences  (RSSs) To maintain the specificity of recombination, V(D)J recombinase recognizes and binds to recombination signal sequences (RSSs) flanking the variable (V), diversity (D), and joining (J) genes segments. RSSs are composed of three elements: a heptamer of seven conserved nucleotides a spacer region of 12 or 23 basepairs in length a nonamer of nine conserved nucleotides

6. Recombination Signal Sequences (RSSs)

7. Mechanism

8. Mechanism

9. Process Progenitor lymphoid cell which through VDJ recombination make an immature B cell with unique antibody that binds to specific antigen. This process occurs in two steps Somatic recombination of heavy chain Somatic recombination of light chain

10. SOMATIC RECOMBINATION OF HEAVY CHAIN LAIQA SHAHID 280-FBAS/BSBIO/F20

11. STRUCTURE OF HEAVY CHAIN The germ line DNA of progenitor B cell has some genes for the heavy chains. Those will make heavy chains of the Ab. In the heavy chain gene we have: a leader segment, V (variable) region, D (Diversity) Segment, J (Joining) segment, and we have the constant region. VDJ recombination involves the VDJ segments. There are many V segments, many D segments, and many J segments. On the heavy chain gene we have also some constant region called as Constant u (Cu) that make Ab for IgM.

12. J and C and in close proximity. However the V region and D region are far away from each other.

13. VDJ RECOMBINATION In the developing B cell, the first recombination event to occur is between one D and one J gene segment of the heavy chain locus. Any DNA between these two gene segments is deleted. This D-J recombination is followed by the joining of one V gene segment, from a region upstream of the newly formed DJ complex, forming a rearranged VDJ gene segment. All other gene segments between V and D segments are now deleted from the cell's genome. Primary  transcript ( unspliced RNA) is generated containing the VDJ region of the heavy chain and both the constant  mu  and  delta  chains ( C μ  and C δ ). (i.e. the primary transcript contains the segments: V-D-J- C μ - C δ ). The primary RNA is processed to add a  polyadenylated  (poly-A) tail after the C μ  chain and to remove sequence between the VDJ segment and this constant gene segment.  Translation  of this mRNA leads to the production of the  IgM  heavy chain protein.

14. SOMATIC RECOMBINATION of light chain   The first step of recombination for the light chains involves the joining of the V and J chains to give a VJ complex before the addition of the constant chain gene during primary transcription. Light chain don’t have a D segment. Two types of chains : kappa and lambda chains, but the immunoglobin rearrange in a similar way so, Both K and L don't have a Diversity segment. J and C regions are close to each other but the variable(v)region is faraway and V always have a leader sequence.

15. VJ recombination First step is Shuffling, in which any of the variable region shuffle with the J segment.e-g.., Vk2 shuffle with Jk4. The second step is Cutting, in which the region between Vk2 and Jk4 ,are deleted or removed. The 3 rd step is Joining, Vk2 and Jk4 join together. Transcription occur, DNA is converted into pre-RNA. After splicing, Pre-RNA is converted into mature RNA. Finally the mature RNA is translated into Igk light chain(protein).

16. Assembly of the Ig μ heavy chain and one of the light chains results in the formation of membrane bound form of the immunoglobulin IgM that is expressed on the surface of the immature B cell.

17. Differnce in recombination When the recombination occurs in constant region. It gives idea about “Which antibody is made” IGG, IGM, IGA, IGE But when the recombination occurs in variable region “Which subtype of antibody is made” It makes the difference in the variable region. It makes 2 IgG different from each other.