Cre-mediated deletion of SMARCA5 disrupts pluripotency in mouse embryonic stem cells

In embryonic stem cells (ESCs), the SWI/SNF, CHD, and INO80 families of ATP-dependent chromatin remodellers have been implicated in maintaining pluripotency-associated gene expression. At the time of this study, the importance of ISWI family remodellers had yet to be defined, and we had sought to assess their involvement. During this time, Barisic et al. (Nature, 2019) elegantly demonstrated that the ISWI homologue SNF2H (Smarca5) is important for nucleosomal periodicity, the binding of select transcription factors, and proper differentiation of mouse ESCs. While we do not dispute their findings to any extent, our experiments have led to slightly different conclusions, and we have chosen to use this platform to share our results. Here, we explore the importance of SNF2H by deriving a conditional knockout mouse ESC line and observing the consequences of SNF2H depletion on the pluripotent state. Cre-mediated deletion of Snf2h disrupts hallmark characteristics of pluripotency, resulting in distinct morphological changes; reduced expression of the master transcription factors Oct4, Sox2, and Nanog; and reduced alkaline phosphatase activity. To understand the mechanisms of SNF2H-mediated regulation, we mapped SNF2H-bound nucleosomes genome-wide. SNF2H is broadly distributed across the genome but is preferentially enriched at active regulatory regions and transcription factor binding sites.