KDM3A and KDM3B Maintain Naïve Pluripotency Through the Regulation of Alternative Splicing.

Histone modifying enzymes play a central role in maintaining cell identity by establishing a conducive chromatin environment for lineage specific transcription factor activity. Pluripotent embryonic stem cells (ESCs) identity is characterized by lower abundance of gene repression associated histone modifications that enables rapid response to differentiation cues. The KDM3 histone demethylase family removes the repressive histone H3 lysine 9 dimethylation (H3K9me2). Here we uncover a surprising role for the KDM3 proteins in the maintenance of the pluripotent state through post-transcriptional regulation. We find through immunoaffinity purification of the KDM3A or KDM3B interactome and proximity ligation assays that KDM3A and KDM3B interact with RNA processing factors such as EFTUD2 and PRMT5. By generating double "degron" ESCs to degrade KDM3A and KDM3B in the rapid timescale of splicing, we find altered splicing, independent of H3K9me2 status. These splicing changes partially resemble the splicing pattern of the more blastocyst-like ground state of pluripotency and occurred in important chromatin and transcription factors such as Dnmt3b, Tbx3 and Tcf12 . Our findings reveal non-canonical roles of histone modifying enzymes in splicing to regulate cell identity.