Functional roles of the chromatin remodeler SMARCA5(SNF2H) in mouse and bovine preimplantation embryos

Upon fertilization, extensive chromatin reprogramming occurs during preimplantation development. Growing evidence reveals species-dependent regulations of this process in mammals. ATP-dependent chromatin remodeling factor SMARCA5 (also known as SNF2H) is required for peri-implantation development in mice. However, the specific functional role of SMARCA5 in preimplantation development and if it is conserved among species remain unclear. Herein, comparative analysis of public RNA-seq datasets reveals that SMARCA5 is universally expressed during oocyte maturation and preimplantation development in mice, cattle, humans and pigs with species-specific patterns. Immunostaining analysis further describes the temporal and spatial changes of SMARCA5 in both mouse and bovine models. siRNA-mediated SMARCA5 depletion reduces the developmental capability and compromises the specification and differentiation of inner cell mass in mouse preimplantation embryos. Indeed, OCT4 is not restricted into the inner cell mass and the formation of epiblast and primitive endoderm disturbed with reduced NANOG and SOX17 in SMARCA5-deficient blastocysts. RNA-seq analysis shows SMARCA5 depletion causes limited effects on the transcriptomics at the morula stage, however, dysregulates 402 genes, including genes involved in transcription regulation and cell proliferation at the blastocyst stage in mice. By comparison, SMARCA5 depletion does not affect the development through the blastocyst stage but significantly compromises the blastocyst quality in cattle. Primitive endoderm formation is greatly disrupted with reduced GATA6 in bovine blastocysts. Overall, our studies demonstrate the importance of SMARCA5 in fostering the preimplantation development in mice and cattle while there are species-specific effects. Mouse embryos were obtained at E3.75 and E4.25 from NC and KD groups (n=2; 20 embryos per group per replicate). RNA isolation was performed by using Arcturus PicoPureRNA Isolation Kit (Applied Biosystems, Foster City, CA) based on the manufacturer's instructions. The separation of mRNAs was completed by using oligo(dT)25 beads. Sequencing libraries were constructed by using NEB Next Ultra RNA Library Prep Kit for Illumina (New England Biolabs, Ipswich, MA) according to the instructions. In brief, mRNAs were fragmented and reverse transcribed. Then, the cDNA library went through end repair, poly(A)-tailing, adaptor ligation, and PCR amplification for 12-15 cycles. Sequencing was conducted with paired-end 150 by Novogene (Beijing, China).