Análisis del papel de las islas CpG en el restablecimiento de los patrones de expresión génica dependientes de enhancers tras la salida de mitosis

Abstract

All cells within an organism typically share the same genetic material. Therefore, the differentiation of individual cell lineages is driven by a specific epigenetic and transcriptional profile, which needs to be tightly regulated to maintain cellular identity. Various genetic and epigenetic elements—such as histones modifications, transcription factors, promoters and enhancers—play a key role in guiding and preserving cell fate. In proliferative cells, transcription is completely halted during mitosis and reinitiated upon entry into G1. To maintain cellular identity, gene expression programs must be re-established after mitosis, including the reactivation of transcription factor genes that play crucial roles in cell identity regulation. These genes are typically controlled by distal enhancers. Here, we hypothesize that CpG-rich enhancers (i.e. enhancers associated with CpG islands) might be particularly important to ensure the timely and precise reactivation of regulatory genes as cells transition from mitosis to G1, thus restoring cell identity. To test this hypothesis, we selected two enhancers that are active in mouse embryonic stem cells (mESC) and created different constructs combining them with or without a CpG island. These constructs were inserted at 100 kb from the Gata6 promoter in mESCs, generating transgenic lines. By evaluating Gata6 expression via RT-qPCR in asynchronous cells, we observed that while the CpG island alone has a negative effect on Gata6 expression, the combination of an active enhancer with a CpG island increases its expression. Although these results are preliminary, the establishment of these cell lines will enable future studies in a mitotic context.