Organization & Expression of Immunoglobulin Genes

1. Organization & Expression of Immunoglobulin Genes Hugh B. Fackrell

2. Organization & Expression of Immunoglobulin Genes Assigned Reading Content Outline Performance Objectives Key terms Key Concepts Short Answer Questions

3. Assigned Reading • Chapter: 7 pp 165-194 • Janis Kuby’s Immunology 3rd Ed

4. Genetic models Multigene Organization of Immunoglobulin Genes Variable-Region Gene Rearrangements Generation of Antibody Diversity Class Switching in C region genes Expression of Ig Genes Regulation of Ig-Gene Transcription Content Outline

7. Genetic models • Germ line vs somatic mutation model • Dryer Bennett: Two gene model • Verification

11. Multigene Organization of Immunoglobulin Genes • lambda chain multigenes • kappa chain multigenes • heavy chain multigenes

16. Variable-Region Gene Rearrangements • V-J rearrangements of light chains • V-D-J rearrangements of heavy chains

20. Mechanisms • recombination signal sequences • enzymatic joining of gene segements • RAG-1 RAG-2 • Defects • Productive vs non productive gene rearrangements • Allelic exclusion

27. Generation of Antibody Diversity • multiple germ line gene segments • combinatorial V-J & V-D-J joining • junctional flexibility • P-nucleotide addition • N-nucleotide addition • Somatic hypermutation • Association of light & heavy chains

31. Class Switching in C Region Genes • Expression of Ig Genes • Differential processing of RNA transcripts of heavy chains • Membrane bound vs secreted Ig • Coexpression of IgM & IgD • Synthesis, assembly and secretion

33. Regulation of Ig-Gene Transcription • DNA rearrangement • Inhibition by T Cells

34. DONE!!!

35. Performance Objectives

36. Key Terms • allelic exclusion, class switching, • combinatorial freedom of chain association,comibinatorial association of • gene segments, Constant (c) gene segments, Diversity (D) gene segemtns, • Palindromes, acceptor junctions, donor junctions, enhancers, exons,

37. 7-9 rule, 12-23 rule, Germline theory, somatic theory, imprecise DNA rerangement, • Insertion of random N regions, introns, Joining (J) gene segments, • junctional diversity, leader sequence, Membrane (M) exons), n regions • promotors, recognition sequences, spacer sequences, somatic hypermutation, • switch recombination. switch (S) regions, variable(V) gene segments

38. Key Concepts • Describe how the number and organization of immunoglobulin gene segements or exons contribute to the generation of antibody diversity • Draw the organization of Kappa light chain genes. • Draw the organization of Lambda light chain genes.

39. Draw the organization of heavy chain genes. • Describe the V-J joining for light chain genes in terms of the 7-9 and the 12-23 rules • Describe the V-D-J joining of heavy chain genes in terms of the 7-9 and the 12-23 rules. • Explain how allelic exclusion leads to cells that produce immunoglobulins with a single antigen binding site.

40. Describe how transcription controls immunoglobulin gene expression • Describe at least four mechanisms that contribute to antibody diversity • Describe the coexpression of IgM and IdD in terms of RNA processsing • Describe the mechanisms for class switching • Correlate B cell differentiation with immunoglobulin gene rearrangements

41. Short Answer Questions

42. Why is it important to have antibody diversity? • Differentiate between the germline theory and the somatic theory of generation of antibody diversity. • How are BOTH germline and somatic mechanisms sources of antibdoy diversity? • Why did the amino acid sequencing of antibody light chains lead Dryer and Bennet to abandon the one gene- one polypeptide theory and propose that two genes code for a single polypeptide?

43. Describe Tonagawa's approach to answering Dreyer and Bennett's hypothesis that two genes code for a single polypeptide. • In addition to showing that DNA seqments come together to form a functional antibody gene, Tonagawa's experiments showed two other things. What were they?

44. The phrases "race car", "Madam I am Adam" and "sex at noon taxes" represent pallindromes in the english language. • What are pallindromes in the genetic code and what is their importance in V region construction? • What are the two DNA recombinational events required to assemble a functional heavy chain V region gene?

45. The two DNA recombinational events required to assemble a functional heavy chain V region gene, are governed by the 7-9 and the 12-23 rules. Explain. • Discuss four mechanisms that contribute to antibody diversity. • Describe the differential splicing of RNA that progresses from membrane bound IgM to secreted IgM.

46. Explain how a particular B cell can secrete different antibody isotypes, yet remain specific for the same epitope. • What are the two stages of class switching? • Dicuss allelic exclusion; what it is and how it is regulated. • List in correct chronological order the events leading to the synthesis of a Kappa light chain and its incorporation into an antibody molecule.

47. List in correct chronological order the events leading to the synthesis of a Gamma chain and its incorporation into an antibody molecule.