Sebastiano, V. | Search bioRxiv

bioRxiv2018

Selection-free, high frequency genome editing by homologous recombination of human pluripotent stem cells using Cas9 RNP and AAV6

Combination of genome editing and human pluripotent stem cells (hPSCs) offers a platform for in vitro disease modeling, drug discovery and personalized stem cell therapeutics. However, incorporation of large modifications using CRISPR/Cas9-based genome editing in hPSCs typically requires the use of selection markers due to low editing efficiencies. Here we report a novel editing technology in hPSCs using Cas9 protein complexed with chemically modified single guide RNA (sgRNA) and recombinant AAV6 (rAAV6) vectors for donor delivery without marker selection. With these components, we demonstrate targeted integration of a 2.2 kb DNA expression cassette in hPSCs at frequencies up to 94% and 67% at the HBB and MYD88 loci, respectively. We used this protocol to correct the homozygous sickle cell disease (SCD) mutation in an iPSC line derived from a SCD patient with a frequency of 63%. This Cas9/AAV6 system allows for both the integration of large gene cassettes and the creation of single nucleotide changes in hPSCs at high frequencies, eliminating the need for multiple editing steps and marker selection, thus increasing the potential of editing human pluripotent cells for both research and translational applications.

bioengineering↗

bioRxiv2016

Single cell analysis of lincRNA expression during human blastocyst differentiation identifies TERT (+) multi-lineage precursor cells

Chromosome instability and aneuploidies occur very frequently in human embryos, impairing proper embryogenesis and leading to cell cycle arrest, loss of cell viability, and developmental failures in 50-80% of cleavage-stage embryos. This high frequency of cellular extinction events represents a significant experimental obstacle challenging analyses of individual cells isolated from human preimplantation embryos. Here, we carried out single cell expression profiling analyses of 241 individual cells recovered from 32 human embryos during the early and late stages of viable human blastocyst differentiation. Classification of embryonic cells was performed solely based on expression patterns of human pluripotency-associated transcripts (HPAT), which represent a family of transposable element-derived lincRNAs highly expressed in human embryonic stem cells (hESCs) and regulating nuclear reprogramming and pluripotency induction. We then validated our findings by analyzing 1,708 individual embryonic cells recovered from more than 100 human embryos and 259 mouse embryonic cells at different stages of preimplantation embryogenesis. Our experiments demonstrate that segregation of human blastocyst cells into distinct sub-populations based on single-cell expression profiling of just three HPATs (HPAT-21; -2; and -15) appears to inform key molecular and cellular events of naive pluripotency induction and accurately captures a full spectrum of cellular diversity during human blastocyst differentiation. HPATs expression-guided spatiotemporal reconstruction of human embryonic development inferred from single-cell expression analysis of viable blastocyst differentiation enabled identification of TERT(+) sub-populations, which are significantly enriched for cells expressing key naive pluripotency regulatory genes and genetic markers of all three major lineages created during human blastocyst differentiation. Results of our analyses suggest that during early stages of preimplantation embryogenesis putative immortal multi-lineage precursor cells (iMPCs) are created, which then differentiate into trophectoderm, primitive endoderm and pluripotent epiblast lineages. We propose that cellular extinction events in cleavage-stage embryos are triggered by premature activation of HPAT lincRNAs reflecting failed iMPCs creation attempts.\n\nHighlightsO_LISingle cell analysis of 1,949 human & 259 mouse embryonic cells\nC_LIO_LIIdentification of 5 most abundant HPAT lincRNAs in viable human blastocysts\nC_LIO_LIExpression profiling of just 3 lincRNAs captures cellular diversity of human blastocysts\nC_LIO_LIIdentification & characterization of TERT(+) multi-lineage precursor cells\nC_LIO_LIMTTH/HPAT lincRNAs regulatory axis of naive pluripotency induction in vivo\nC_LI

genomics↗