Developmental stage-specific A-to-I editing pattern in the postnatal pineal gland of pigs(Sus scrofa)

Background: RNA editing is a widespread post-transcriptional modification mechanism in mammalian genomes.Although many editing sites have been identified in domestic pigs(Sus scrofa), little is known about the characteristics and dynamic regulation of RNA editing in the pineal gland(PG), a small neuroendocrine gland that synthesizes and secretes melatonin, which is primarily responsible to modulate sleep patterns.Results: This study analyzed the expression of adenosine-to-inosine(A-to-I) editing regulators and profiled the first dynamic A-to-I RNA editome during postnatal PG development. The results identified ADAR1 as the most abundantly expressed ADAR enzyme, which was down-regulated during postnatal PG development. Furthermore,47,284 high-confidence RNA editing sites were identified, the majority of which(93.6%) were of the canonical A-to-I editing type, followed by C-to-T editing. Analysis of its characteristics showed that the A-to-I editing sites mostly localized in SINE retrotransposons PRE-1/Pre0_SS. Moreover, a strong deficiency and preference for guanine nucleotides at positions of one base upstream or downstream were found, respectively. The overall editing level at the puberty stage was higher than at both infancy and adulthood stages. Additionally, genome-wide RNA editing was found to exhibit a dynamic stage-specific fashion(postnatally). Genes that underwent developmental changes in RNA editing were associated with catabolic processes as well as protein localization and transport functions,implying that RNA editing might be responsible for the molecular machineries of the postnatal developing PG.Remarkably, RNA editing in 3′-UTRs might regulate gene expression by influencing miRNA binding during PG development.Conclusions: This study profiles the first comprehensive developmental RNA editome in the pig PG, which contributes to the understanding of the importance of post-transcriptionally mediated regulation during mammalian postnatal PG development. Moreover, this study widely extends RNA editome resources in mammals.

Overcoming barriers to the clinical utilization of iPSCs:reprogramming efficiency,safety and quality

Differentiated cells can be reprogrammed into pluripotent stem cells,known as“induced pluripotent stem cells”(iPSCs),through the overexpression of defined transcription factors.The creation of iPSC lines has opened new avenues for patient-specific cell replacement therapies for regenerative medicine.However,the clinical utilization of iPSCs is largely impeded by two limitations.The first limitation is the low efficiency of iPSCs generation from differentiated cells.The second limitation is that many iPSC lines are not authentically pluripotent,as many cell lines inefficiently differentiate into differentiated cell types when they are tested for their ability to complement embryonic development.Thus,the“quality”of iPSCs must be increased if they are to be differentiated into specialized cell types for cell replacement therapies.Overcoming these two limitations is paramount to facilitate the widespread employment of iPSCs for therapeutic purposes.Here,we summarize recent progress made in strategies enabling the efficient production of high-quality iPSCs,including choice of reprogramming factors,choice of target cell type,and strategies to improve iPSC quality.

Progress,problems and prospects of porcine pluripotent stem cells

Pluripotent stem cells(PSCs),including embryonic stem cells(ESCs)and induced PSCs(iPSCs),can differentiate into cells of the three germ layers,suggesting that PSCs have great potential for basic developmental biology research and wide applications for clinical medicine.Genuine ESCs and iPSCs have been derived from mice and rats,but not from livestock such as the pig-an ideal animal model for studying human disease and regenerative medicine due to similarities with human physiologic processes.Efforts to derive porcine ESCs and iPSCs have not yielded high-quality PSCs that can produce chimeras with germline transmission.Thus,exploration of the unique porcine gene regulation network of preimplantation embryonic development may permit optimization of in vitro culture systems for raising porcine PSCs.Here we summarize the recent progress in porcine PSC generation as well as the problems encountered during this progress and we depict prospects for generating porcine naive PSCs.

Pluripotent stem cells secrete Activin A to improve their epiblast competency after injection into recipient embryos

It is not fully clear why there is a higher contribution of pluripotent stem cells （PSCs） to the chimera produced by injection of PSCs into 4-cell or 8-cell stage embryos compared with blastocyst injection. Here, we show that not only embryonic stem cells （ESCs） but also induced pluripotent stem cells （iPSCs） can generate F0 nearly 100% donor cell-derived mice by 4-cell stage embryo injection, and the approach has a ＂dose effect＂. Through an analysis of the PSC-secreted proteins, Activin A was found to impede epiblast （EPI） lineage development while promoting trophectoderm （TE） differentiation, resulting in replacement of the EPI lineage of host embryos with PSCs. Interestingly, the injection of ESCs into blastocysts cultured with Activin A （cultured from 4-cell stage to early blastocyst at E3.5） could increase the contribution of ESCs to the chimera. The results indicated that PSCs secrete protein Activin A to improvetheir EPI competency after injection into recipient embryos through influencing the development of mouse early embryos. This result is useful for optimizing the chimera production system and for a deep understand- ing of PSCs effects on early embryo development.