Manipulation of SMARCA2 and SMARCA4 transcript levels in porcine embryos differentially alters development and expression of SMARCA1, SOX2, NANOG, and EIF1.

Epigenetic reprogramming plays a pivotal role during embryogenesis, including both covalent and non-covalent modifications to chromatin. In this study, we investigated the role of SNF2 chromatin remodeling ATPases (SMARCA2 (previously known as BRAHMA), SMARCA4 (previously known as BRG1), SMARCA5 (previously known as SNF2H), SMARCA1 (previously known as SNF2L), CHD3, and CHD5) during porcine preimplantation embryonic development. Transcript levels for these ATPases change dynamically throughout development. We also investigated the effect of altering transcript levels of SMARCA2 and SMARCA4 via mRNA injection. Overexpression of SMARCA2 and SMARCA4 severely impaired embryo development. Results from these experiments show that embryos injected with SMARCA2 mRNA arrest between the four-cell and blastocyst stages. However, embryos injected with either wild-type SMARCA4 or a dominant negative variant or SMARCA4 arrest before zygotic genome activation. No differences in transcript abundance of SOX2, POU5F1, NANOG, and EIF1 (previously known as eIF1A) were detected after injection with SMARCA2 or its dominant negative variant at 48 h post-injection. Conversely, embryos injected with wild-type SMARCA4 and its dominant negative variant possessed altered expression of these genes. Examination of SNF2-type ATPase transcript abundance across all treatment groups revealed that only SMARCA1 was altered following injection with wild-type SMARCA2 and wild-type and dominant negative SMARCA4. We conclude that the arrest in porcine embryo development observed after injection is specific to the ATPase injected. Our data strongly support the hypothesis that SMARCA2 and SMARCA4 play different but fundamental roles controlling gene expression during early mammalian embryogenesis.

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