Regulation of Zygotic Genome and Cellular Pluripotency

Alternative polyadenylation coordinates embryonic development, sexual dimorphism and longitudinal growth in Xenopus tropicalis

RNA alternative polyadenylation contributes to the complexity of information transfer from genome to phenome, thus amplifying gene function. Here, we report the first X. tropicalis resource with 127,914 alternative polyadenylation (APA) sites derived from embryos and adults. Overall, APA networks play central roles in coordinating the maternal-zygotic transition (MZT) in embryos, sexual dimorphism in adults and longitudinal growth from embryos to adults. APA sites coordinate reprogramming in embryos before the MZT, but developmental events after the MZT due to zygotic genome activation. The APA transcriptomes of young adults are more variable than growing adults and male frog APA transcriptomes are more divergent than females. The APA profiles of young females were similar to embryos before the MZT. Enriched pathways in developing embryos were distinct across the MZT and noticeably segregated from adults. Briefly, our results suggest that the minimal functional units in genomes are alternative transcripts as opposed to genes.

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.

The Vox mRNA and protein expression in zebrafish Pou5f3 MZspg mutant embryos

The transcription factor of pluripotency Pou5f3 is considered to enhance the Vox expression. This conclusion was based on the study of mRNA expression, but the expression of the Vent-family proteins was not analyzed. We compare spatiotemporal distribution of the Vox and Vent mRNAs and the proteins in embryos of wild type zebrafish (WT) and MZspg (spiel ohne grenzen) mutants devoid of both maternal and embryonic Pou5f3 functions. We revealed the Vox mRNA and its protein in both the WT and mutant embryos during the cleavage period. They were probably prestored maternally. The quantity of the prestored protein, unlike the mRNA, in the mutants was visibly less than that in the WT embryos. The Pou5f3, therefore, had no influence on the Vox mRNA maternal synthesis, but it affected the maternal Vox protein synthesis. During the blastula and gastrula periods the MZspg mutants, but not the WT, failed to synthesize the new Vox mRNA, while the prestored maternal mRNA was gradually degrading. At these stages the WT and mutant embryos displayed minor visual quantitative difference in staining of Vox protein. The Vent mRNA was not maternally prestored and its zygote synthesis slightly depended on the Pou5f3. The Vent protein in mutants and WT was synthesized on the new zygote mRNAs. By the gastrula period, the Vent staining of the WT and mutant embryos were almost comparable. The data obtained suggest the existence of mechanisms sustaining a required Vox and Vent proteins level, but these mechanisms are not directly dependent on the Pou5f3.

Advances and Challenges on Cancer Cells Reprogramming Using Induced Pluripotent Stem Cells Technologies

Cancer cells transformation into a normal state or into a cancer cell population which is less tumorigenic than the initial one is a challenge that has been discussed during last decades and it is still far to be solved. Due to the highly heterogeneous nature of cancer cells, such transformation involves many genetic and epigenetic factors which are specific for each type of tumor. Different methods of cancer cells reprogramming have been established and can represent a possibility to obtain less tumorigenic or even normal cells. These methods are quite complex, thus a simple and efficient method of reprogramming is still required. As soon as induced pluripotent stem cells (iPSC) technology, which allowed to reprogram terminally differentiated cells into embryonic stem cells (ESC)-like, was developed, the method strongly attracted the attention of researches, opening new perspectives for stem cell (SC) personalized therapies and offering a powerful in vitro model for drug screening. This technology is also used to reprogram cancer cells, thus providing a modern platform to study cancer-related genes and the interaction between these genes and the cell environment before and after reprogramming, in order to elucidate the mechanisms of cancer initiation and progression. The present review summarizes recent advances on cancer cells reprogramming using iPSC technology and shows the progress achieved in such field.