Predicting differentiation potential of human pluripotent stem cells:Possibilities and challenges

The capability of human pluripotent stem cell(hPSC)lines to propagate indefinitely and differentiate into derivatives of three embryonic germ layers makes these cells be powerful tools for basic scientific research and promising agents for translational medicine.However,variations in differentiation tendency and efficiency as well as pluripotency maintenance necessitate the selection of hPSC lines for the intended applications to save time and cost.To screen the qualified cell lines and exclude problematic cell lines,their pluripotency must be confirmed initially by traditional methods such as teratoma formation or by highthroughput gene expression profiling assay.Additionally,their differentiation potential,particularly the lineage-specific differentiation propensities of hPSC lines,should be predicted in an early stage.As a complement to the teratoma assay,RNA sequencing data provide a quantitative estimate of the differentiation ability of hPSCs in vivo.Moreover,multiple scorecards have been developed based on selected gene sets for predicting the differentiation potential into three germ layers or the desired cell type many days before terminal differentiation.For clinical application of hPSCs,the malignant potential of the cells must also be evaluated.A combination of histologic examination of teratoma with quantitation of gene expression data derived from teratoma tissue provides safety-related predictive information by detecting immature teratomas,malignancy marker expression,and other parameters.Although various prediction methods are available,distinct limitations remain such as the discordance of results between different assays and requirement of a long time and high labor and cost,restricting their wide applications in routine studies.Therefore,simpler and more rapid detection assays with high specificity and sensitivity that can be used to monitor the status of hPSCs at any time and fewer targeted markers that are more specific for a given desired cell type are urgently needed.

A finTRIM member 100 (FTR100) is unique to Otomorpha fish for constitutive regulation of IFN response

Vertebrate interferon(IFN)expression is fine-tuned in order to avoid excessive tissue injury under normal conditions and during virus infection.FinTRIM(fish novel TRIM,FTR)proteins are reported to regulate the fish IFN response.Here,we identify a novel finTRIM gene from yellow catfish(Pelteobagrus fulvidraco),which is sequentially named PfFTR100 according to the nomenclature rule in zebrafish.Genome-wide analyses reveal that FTR100 is unique to Otomorpha fish,with a single copy in spite of additional genome duplication in some fish species.Considering that few of the 99 finTRIM genes identified in zebrafish are conserved in main fish branches and most,such as FTR100,are unique to distinct branches due to lineage-specific expansion of finTRIM genes,we develop a nomenclature for newly cloned finTRIM genes from different fish species.PfFTR100 mRNA is not induced by virus infection,with a relatively high expression level comparable to that of cellular IFN and some IFN-stimulated genes(ISGs)in virally-infected tissues.However,ectopically-expressed PfFTR100 protein is attenuated in virally-infected cells through the proteasomal-dependent pathway.Overexpression of PfFTR100 promotes SVCV replication by downregulating the constitutive and inducible IFN response via a mechanism by which PfFTR100 targets IRF3 and IRF7 to attenuate their mRNA levels rather than their protein levels.Our results indicate that yellow catfish FTR100 is essential for homeostatic regulation of fish tonic IFN response.

Argonaute(AGO)proteins play an essential role in mediating BMP9-induced osteogenic signaling in mesenchymal stem cells(MSCs)

As multipotent progenitor cells,mesenchymal stem cells(MSCs)can renew themselves and give rise to multiple lineages including osteoblastic,chondrogenic and adipogenic lineages.It’s previously shown that BMP9 is the most potent BMP and induces osteogenic and adipogenic differentiation of MSCs.However,the molecular mechanism through which BMP9 regulates MSC differentiation remains poorly understood.Emerging evidence indicates that noncoding RNAs,especially microRNAs,may play important roles in regulating MSC differentiation and bone formation.As highly conserved RNA binding proteins,Argonaute(AGO)proteins are essential components of the multi-protein RNA-induced silencing complexes(RISCs),which are critical for small RNA biogenesis.Here,we investigate possible roles of AGO proteins in BMP9-induced lineage-specific differentiation of MSCs.We first found that BMP9 upregulated the expression of Ago1,Ago2 and Ago3 in MSCs.By engineering multiplex siRNA vectors that express multiple siRNAs targeting individual Ago genes or all four Ago genes,we found that silencing individual Ago expression led to a decrease in BMP9-induced early osteogenic marker alkaline phosphatase(ALP)activity in MSCs.Furthermore,we demonstrated that simultaneously silencing all four Ago genes significantly diminished BMP9-induced osteogenic and adipogenic differentiation of MSCs and matrix mineralization,and ectopic bone formation.Collectively,our findings strongly indicate that AGO proteins and associated small RNA biogenesis pathway play an essential role in mediating BMP9-induced osteogenic differentiation of MSCs.