We’re moving the GATK website, docs and forum to a new platform. Read the full story and breakdown of key changes on this blog.
If you happen to see a question you know the answer to, please do chime in and help your fellow community members. We encourage our fourm members to be more involved, jump in and help out your fellow researchers with their questions. GATK forum is a community forum and helping each other with using GATK tools and research is the cornerstone of our success as a genomics research community.We appreciate your help!
Test-drive the GATK tools and Best Practices pipelines on Terra
Check out this blog post to learn how you can get started with GATK and try out the pipelines in preconfigured workspaces (with a user-friendly interface!) without having to install anything.
Bisulfite sequencing / Cytosine methylation
Cytosine methylation is a key component in epigenetic regulation of gene expression and frequently occurs at CpG sites throughout the genome. Bisulfite sequencing is a technique used to analyze the genome-wide methylation profiles on a single nucleotide level [doi:10.1093/nar/gki901]. Sodium bisulfite efficiently and selectively deaminates unmethylated cytosine residues to uracil without affecting 5-methyl cytosine (methylated). Using restriction enzymes and PCR to enrich for regions of the genome that have high CpG content, the resulting reduced genome comprises ~1% of the original genome but includes key regulatory sequences as well as repeated regions.
The protocol involves several steps. First, genomic DNA is digested with a restriction endonuclease such as MspI, which targets CG dinucleotides. This results in DNA fragments with CG at the ends. Next, the fragments are size selected (via gel electrophoresis), which facilitates the enrichment of CpG-containing sequences. This is followed by bisulfite treatment, which converts unmethylated C nucleotides to uracil (U) while methylated cytosines will remain intact. The bisulfite-treated DNA is amplified with a proofreading-deficient DNA polymerase to facilitate amplification of both methylated cytosines as well as the C -> U converted bases. Subsequent to PCR amplification, each original unmethylated cytosine will be converted to either a T (+ strand) or an A (- strand), while methylated C will remain a C (+ strand) or a G (- strand). The PCR products are then sequenced using conventional methods and aligned to a reference.