Dynamic changes in expression levels and histone modifications were analyzed in a CHO-K1 batch culture by capturing expression profiles every 24 hours and histone modifications every 12 hours for understanding the contribution of epigenetic regulation on culture behavior of CHO cells.. Epigenetic regulation in Chinese Hamster Ovary cell lines

Chinese Hamster Ovary (CHO) cells are the main tool for therapeutic protein production with “human like” glycosylation patterns. Beside genetic alterations, epigenetic regulation, such as histone modifications, can play a role in determining altered production characteristics. However, so far very little detailed data on epigenetic regulation in CHO cells is available. Histone modifications regulate transcriptional “on” or “off” states of genes and influence chromatin condensation and state. Modifications are mainly based on post-translational modifications occurring within the histone N-terminal tails and are responsible for structural changes in histones or their binding to DNA. As these modifications are conserved between different species, we focus on the same six histone H3 modifications described in the International Human Epigenome Consortium. We developed a protocol for Chromatin immunoprecipitation (ChIP) for CHO cells, including cell fixation, crosslinking to stabilize protein-DNA interactions, chromatin shearing, immunoprecipitation, DNA purification, control of the immunoprecipitated DNA by RT PCR, followed by Next Generation Sequencing. As no previous data for CHO cell lines are available, we needed to explore patterns of histone modifications typical for CHO cells to enable verification of the protocol. Using this protocol, dynamic changes in histone modifications were analysed in a CHO-K1 batch culture taking samples every 12 hours for an initial assessment of the contribution of epigenetic regulation on culture behavior of CHO cells.