Acquisition of pluripotency in the chick embryo occurs during intrauterine embryonic development via a unique transcriptional network
Background Acquisition of pluripotency by transcriptional regulatory factors is an initial developmental event that is required for regulation of cell fate and lineage specification during early embryonic development. The evolutionarily conserved core transcriptional factors regulating the pluripotency network in fishes, amphibians, and mammals have been elucidated. There are also species-specific maternally inherited transcriptional factors and their intricate transcriptional networks important in the acquisition of pluripotency. In avian species, however, the core transcriptional network that governs the acquisition of pluripotency during early embryonic development is not well understood. Results We found that chicken NANOG (cNANOG) was expressed in the stages between the pre-ovulatory follicle and oocyte and was continuously detected in Eyal-Giladi and Kochav stage I (EGK.I) to X. However, cPOUV was not expressed during folliculogenesis, but began to be detectable between EGK.V and VI. Unexpectedly, cSOX2 could not be detected during folliculogenesis and intrauterine embryonic development. Instead of cSOX2, cSOX3 was maternally inherited and continuously expressed during chicken intrauterine development. In addition, we found that the pluripotency-related genes such as cENS-1, cKIT, cLIN28A, cMYC, cPRDM14, and cSALL4 began to be dramatically upregulated between EGK.VI and VIII. Conclusion These results suggest that chickens have a unique pluripotent circuitry since maternally inherited cNANOG and cSOX3 may play an important role in the initial acquisition of pluripotency. Moreover, the acquisition of pluripotency in chicken embryos occurs at around EGK.VI to VIII. ; This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No.2015R1A3A2033826) and the International Research & Development Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning of Korea (NRF-2016K1A3A1A21005676).
