Skip to main content
Duke University Libraries
DukeSpace Scholarship by Duke Authors
  • Login
  • Ask
  • Menu
  • Login
  • Ask a Librarian
  • Search & Find
  • Using the Library
  • Research Support
  • Course Support
  • Libraries
  • About
View Item 
  •   DukeSpace
  • Theses and Dissertations
  • Duke Dissertations
  • View Item
  •   DukeSpace
  • Theses and Dissertations
  • Duke Dissertations
  • View Item
JavaScript is disabled for your browser. Some features of this site may not work without it.

Epigenetic Regulation of Aicda Transcription in B Cells

Thumbnail
View / Download
502.6 Kb
Date
2012
Author
Kodali, Srikanth
Advisors
Reichert, William
Unniraman, Shyam
Repository Usage Stats
596
views
257
downloads
Abstract

Activation-induced cytidine deaminase (AID), encoded by the Aicda gene, is indispensable for secondary antibody diversification through somatic hypermutation (SHM) and class switch recombination (CSR). It is expressed predominantly in germinal center (GC) B cells, where it deaminates cytosine to uracil in the DNA of immunoglobulin (Ig) genes, triggering mutagenesis (SHM) or deletional recombination events (CSR). However, when misregulated, AID can also mutate non-Ig genes, including proto-oncogenes, thereby contributing to genomic instability and cancer. Due to its potentially deleterious effects, AID expression must be tightly controlled. At the transcriptional level, Aicda is regulated by four highly conserved cis-regulatory regions (Regions 1-4). Region 1 contains the promoter, and is responsible for basal transcription of Aicda. Region 2 contains both enhancer and silencer elements, but functions as a negative regulatory region, restricting AID expression to antigen-activated B cells. Region 3 is reported to be essential for normal AID expression, but its role is otherwise unclear. Region 4, which contains two STAT6 sites essential for its function, provides enhancer activity in response to cytokine stimulation and is responsible for the high levels of AID expression found in GC B cells. Epigenetic mechanisms could add another layer of control to the regulation of Aicda; however, little research has been done in this regard. In this study, I investigated the role of DNA methylation in the cis-regulation of Aicda transcription. Through bisulfite sequencing of splenic mouse B cell DNA, I demonstrate that Region 4 is highly methylated in naïve B cells, but becomes demethylated in activated B cells. This is in contrast to Region 2, which I found to be constitutively unmethylated, and Region 1, which only becomes partially demethylated. Using quantitative methylation-specific PCR (qMSP), I show that loss of methylation in Region 4 correlates positively with cell division number, consistent with a passive mechanism of demethylation. I also show that demethylation in Region 4 cannot be achieved by cell proliferation alone, and that it depends upon induction of AID expression (via IL-4 stimulation). However, bisulfite sequencing of CH12F3-2 cell DNA shows that demethylation by itself is insufficient to activate AID expression. Taken together, the data suggests that IL-4 induces STAT6 to bind to its cognate sites in Region 4 and inhibit DNMT1, likely through chromatin reorganization, triggering passive demethylation during the induction of Aicda transcription.

Type
Dissertation
Department
Biomedical Engineering
Subject
Immunology
Genetics
Permalink
https://hdl.handle.net/10161/5865
Citation
Kodali, Srikanth (2012). Epigenetic Regulation of Aicda Transcription in B Cells. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/5865.
Collections
  • Duke Dissertations
More Info
Show full item record
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

Rights for Collection: Duke Dissertations


Works are deposited here by their authors, and represent their research and opinions, not that of Duke University. Some materials and descriptions may include offensive content. More info

Make Your Work Available Here

How to Deposit

Browse

All of DukeSpaceCommunities & CollectionsAuthorsTitlesTypesBy Issue DateDepartmentsAffiliations of Duke Author(s)SubjectsBy Submit DateThis CollectionAuthorsTitlesTypesBy Issue DateDepartmentsAffiliations of Duke Author(s)SubjectsBy Submit Date

My Account

LoginRegister

Statistics

View Usage Statistics
Duke University Libraries

Contact Us

411 Chapel Drive
Durham, NC 27708
(919) 660-5870
Perkins Library Service Desk

Digital Repositories at Duke

  • Report a problem with the repositories
  • About digital repositories at Duke
  • Accessibility Policy
  • Deaccession and DMCA Takedown Policy

TwitterFacebookYouTubeFlickrInstagramBlogs

Sign Up for Our Newsletter
  • Re-use & Attribution / Privacy
  • Harmful Language Statement
  • Support the Libraries
Duke University