Effect of SARS-CoV-2 infection in early pregnancy on placental development

Dear Editor,Since the COVID-19 pandemic, the potential risks associated with maternal SARS-CoV-2 infection and its effect on fetal development have been a subject of considerable public concern. Previous studies have shown that SARS-CoV-2 infection during pregnancy may increase the incidence of adverse outcomes.

Pivotal role for long noncoding RNAs in zygotic genome activation in mice

Vertebrate life begins with fertilization,and then the zygote genome is activated after transient silencing,a process termed zygotic genome activation(ZGA).Despite its fundamental role in totipotency and the initiation of life,the precise mechanism underlying ZGA initiation remains unclear.The existence of minor ZGA implies the possible critical role of noncoding RNAs in the initiation of ZGA.Here,we delineate the expression profile of long noncoding RNAs(lncRNAs)in early mouse embryonic development and elucidate their critical role in minor ZGA.Compared with protein-coding genes(PCGs),lncRNAs exhibit a stronger correlation with minor ZGA.Distinct H3K9me3 profiles can be observed between lncRNA genes and PCGs,and the enrichment of H3K9me3 before ZGA might explain the suspended expression of major ZGA-related PCGs despite possessing PolII pre-configuration.Furthermore,we identified the presence of PolII-enriched MuERV-L around the transcriptional start site of minor ZGA-related lncRNAs,and these repeats are responsible for the activation of minor ZGA-related lncRNAs and subsequent embryo development.Our study suggests that MuERV-L mediates minor ZGA lncRNA activation as a critical driver between epigenetic reprogramming triggered by fertilization and the embryo developmental program,thus providing clues for understanding the regulatory mechanism of totipotency and establishing bona fide totipotent stem cells.

Integrated transcriptome analysis of human iPS cells derived from a fragile X syndrome patient during neuronal differentiation

Fragile X syndrome(FXS) patients carry the expansion of over 200 CGG repeats at the promoter of fragile X mental retardation 1(FMR1), leading to decreased or absent expression of its encoded fragile X mental retardation protein(FMRP). However, the global transcriptional alteration by FMRP deficiency has not been well characterized at single nucleotide resolution, i.e., RNA-seq. Here,we performed in-vitro neuronal differentiation of human induced pluripotent stem(iPS) cells that were derived from fibroblasts of a FXS patient(FXS-iPSC). We then performed RNA-seq and examined the transcriptional misregulation at each intermediate stage during in-vitro differentiation of FXS-iPSC into neurons. After thoroughly analyzing the transcriptomic data and integrating them with those from other platforms, we found up-regulation of many genes encoding TFs for neuronal differentiation(WNT1, BMP4,POU3F4, TFAP2 C, and PAX3), down-regulation of potassium channels(KCNA1, KCNC3, KCNG2, KCNIP4, KCNJ3, KCNK9,and KCNT1) and altered temporal regulation of SHANK1 and NNAT in FXS-iPSC derived neurons, indicating impaired neuronal differentiation and function in FXS patients. In conclusion, we demonstrated that the FMRP deficiency in FXS patients has significant impact on the gene expression patterns during development, which will help to discover potential targeting candidates for the cure of FXS symptoms.

H3K27me3 Signal in the Cis Regulatory Elements Reveals the Differentiation Potential of Progenitors During Drosophila Neuroglial Development

Drosophila neural development undergoes extensive chromatin remodeling and precise epigenetic regulation.However,the roles of chromatin remodeling in establishment and maintenance of cell identity during cell fate transition remain enigmatic.Here,we compared the changes in gene expression,as well as the dynamics of nucleosome positioning and key histone modifications between the four major neural cell types during Drosophila neural development.We find that the neural progenitors can be separated from the terminally differentiated cells based on their gene expression profiles,whereas nucleosome distribution in the flanking regions of transcription start sites fails to identify the relationships between the progenitors and the differentiated cells.H3K27me3 signal in promoters and enhancers can not only distinguish the progenitors from the differentiated cells but also identify the differentiation path of the neural stem cells(NSCs)to the intermediate progenitor cells to the glial cells.In contrast,H3K9ac signal fails to identify the differentiation path,although it activates distinct sets of genes with neuron-specific and glia-related functions during the differentiation of the NSCs into neurons and glia,respectively.Together,our study provides novel insights into the crucial roles of chromatin remodeling in determining cell type during Drosophila neural development.

BMP4 preserves the developmental potential of mESCs through Ube2s-and Chmp4b-mediated chromosomal stability safeguarding

Chemically defined medium is widely used for culturing mouse embryonic stem cells(mESCs),in which N2B27 works as a substitution for serum,and GSK3βand MEK inhibitors(2i)help to promote ground-state pluripo-tency.However,recent studies suggested that MEKi might cause irreversible defects that compromise the developmental potential of mESCs.Here,we demon-strated the deficient bone morphogenetic protein(BMP)signal in the chemically defined condition is one of the main causes for the impaired pluripotency.Mechanisti-cally,activating the BMP signal pathway by BMP4 could safeguard the chromosomal integrity and proliferation capacity of mESCs through regulating downstream tar-gets Ube2s and Chmp4b.More importantly,BMP4 pro-motes a distinct in vivo developmental potential and a long-term pluripotency preservation.Besides,the pluripotent improvements driven by BMP4 are superior to those by attenuating MEK suppression.Taken together,our study shows appropriate activation of BMP signal is essential for regulating functional pluripotency and reveals that BMP4 should be applied in the serum-free culture system.

Genome transfer for the prevention of female infertility caused by maternal gene mutation

Poor oocyte quality is associated with early embryo developmental arrest and infertility.Maternal gene plays crucial roles in the regulation of oocyte maturation,and its mutation is a common cause of female infertility.However,how to improve oocyte quality and develop effective therapy for maternal gene mutation remains elusive.Here,we use Zar1 as an example to assess the feasibility of genome transfer to cure maternal gene mutationecaused female infertility.We first discover that cytoplasmic deficiency primarily leads to Zar1-null embryo developmental arrest by disturbing maternal transcript degradation and minor zygotic genome activation(ZGA)during the maternal-zygotic transition.We next perform genome transfer at the oocyte(spindle transfer or polar body transfer)and zygote(early pronuclear transfer or late pronuclear transfer)stages to validate the feasibility of preventing Zar1 mutationecaused infertility.We finally demonstrate that genome transfer either at the oocyte or at the early pronuclear stage can support normal preimplantation embryo development and produce live offspring.Moreover,those pups grow to adulthood and show normal fertility.Therefore,our findings provide an effective basis of therapies for the treatment of female infertility caused by maternal gene mutation.