The role of RHOA signaling in trophectoderm cell-fate decision in cattle

• Published in: Biochemical and biophysical research communications Vol. 528; no. 4; pp. 713 - 718
• Main Authors: Kohri, Nanami, Akizawa, Hiroki, Iisaka, Sakie, Bai, Hanako, Takahashi, Masashi, Kawahara, Manabu
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 06.08.2020
• Subjects: Animals; Blastocyst; Blastocyst - cytology; Blastocyst - metabolism; Bovine; Cattle - embryology; Cattle - physiology; Differentiation; Ectoderm - cytology; Ectoderm - embryology; Ectoderm - metabolism; Embryo Culture Techniques; Female; Fertilization in Vitro; Hippo signaling pathway; Pregnancy; RHOA activity; rhoA GTP-Binding Protein - metabolism; Signal Transduction; Trophectoderm; YAP1; TEAD4; ROCK; Bovine; CDX2; D; RHOA activity; Blastocyst; RHOA; Trophectoderm; OCT4; C3; TE; ICM; IVF; iICM; Hippo signaling pathway; Differentiation
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2020.05.210

Mammalian blastocysts are composed of two distinct cell lineages, namely the inner cell mass (ICM) and trophectoderm (TE). TE cells that give rise to the embryonic placenta are marked by an exclusive expression of the key determinant transcription factor, CDX2. Although Hippo signaling pathway is known to be responsible for this TE-specific expression of CDX2, the upstream regulator of this pathway in mammalian embryos is still controversial. In the present study, the involvement of the small molecular G protein, RHOA, in TE cell-fate decision in cattle was investigated. Inhibition of RHOA by the specific inhibitor, C3 transferase (C3), severely impaired the blastocyst formation. Further, C3 treatment significantly decreased the number of blastomeres with nuclearized YAP1, the prominent effector of Hippo pathway. An artificial isolation of ICM cells from blastocysts followed by the continuing culture to regenerate TE cells was conducted and showed that TE re-emergence from the isolated ICM is governed by Hippo pathway and suppressed by C3 treatment like that observed in developing embryos. Finally, the long-term exposure to C3 suggests the presence of alternative regulators of CDX2 expression other than RHOA signaling because there were still CDX2-positive cells after C3 treatment. These results demonstrated that RHOA signaling plays a significant role in TE cell-fate decision by regulating Hippo pathway in cattle. •RHOA signaling is required for blastocyst formation in cattle.•Inhibition of RHOA signaling reduces the number of blastomeres with nuclearized YAP1.•TE reemergence from iICM is similar to TE differentiation in developing embryos.•RHOA signaling is not the sole regulator of CDX2 expression in bovine TE cells.