The Dm element located in the Igκ locus is hypermethylated in primary RAG- deficient pre-B cells

Abstract

The Igκ locus undergoes a series of epigenetic changes, such as active histone modifications and DNA demethylation, to participate in V(D)J recombination, which is initiated by RAG endonuclease (also known as RAG1/RAG2), during B cell development in the bone marrow. We previously showed that RAG2 is involved in Igκ locus demethylation in RAG-deficient pre-B cells. The Dm element is located in the Igκ locus and has the highest density of CpG sites. Here, we performed a bisulfite DNA-modification assay and chromatin immunoprecipitation (ChIP) experiment to analyze the epigenetics of the Dm element. We found that the Dm element was hypermethylated in RAG deficiency pre-B cells. However, the Dm element was demethylated in splenic B cells. Moreover, the Dm element exhibited high levels of active histone modifications, such as H3K27Ac and H3K9Ac, and binding of Pax5 to it was detected in B cells. In conclusion, our findings indicate that the methylation status of the Dm element undergoes changes in splenic mature B cells. These results provide new insights into the mechanisms of Igκ locus methylation regulation during B cell development.