Reduced Representation Bisulfite Sequencing (RRBS).

Reduced representation bisulfite sequencing (RRBS) enriches CpG-rich genomic regions using the MspI restriction enzyme-which cuts DNA at all CCGG sites, regardless of their DNA methylation status at the CG site-and enables the measurement of DNA methylation levels at 5% ~ 10% of all CpG sites in the mammalian genome. RRBS has been utilized in a large number of studies as a cost-effective method to investigate DNA methylation patterns, mainly at gene promoters and CpG islands. Here, we describe protocols for gel-free preparation of RRBS libraries, quality control, sequencing, and data analysis. Our protocols typically require nine cycles of polymerase chain reaction (PCR) amplification to obtain a sufficient amount of library for sequencing when 100 ng of genomic DNA is used as a starting material; moreover, it takes 3 days to complete library preparation and quality control procedures for up to eight samples.