Simultaneous CRISPR-on activation of TFAP2C and SMARCA4 promotes development of trophoblast-fate cells in bovine embryos.

Assisted reproductive techniques are widely used to produce domestic animal embryos for commercial or research purposes. In cattle, abnormal trophoblast cell differentiation during embryo development causes pregnancy and placentation failures. The CRISPR-on system has been successfully used in bovine embryos to individually activate early trophoblast lineage genes TFAP2C and SMARCA4. This study evaluates the effect of CRISPR-on activation of early and advanced trophoblast-related genes in bovine zygotes to promote trophectoderm differentiation. In one experiment, RNA was microinjected to simultaneously activate TFAP2C and SMARCA4; in another, circular DNA was microinjected to induce CDX2 or GATA3 expression separately. Controls included groups without small guide RNAs (sgRNAs, SHAM) and non-injected embryos (IVF). RNA microinjection transiently and simultaneously increased TFAP2C, SMARCA4, and downstream gene expression, producing a prolonged effect beyond individual gene activation. This led to a significant increase in trophectoderm cells at the blastocyst stage. Individual activation of CDX2 and GATA3 was effective, also inducing upstream genes without altering trophectoderm cell percentages. Neither RNA nor DNA microinjection affected blastocyst production compared to IVF. This work demonstrates the successful increase of trophoblast cells in bovine embryos using CRISPR-on, offering a useful strategy for IVF or SCNT embryos. The CRISPR-dCas9VP160 system may also aid understanding of trophoblast lineage signaling during development.