Nature biotechnology最新文献

Pooled genetic screening with CRISPR–Cas9 has enabled genome-wide, high-resolution mapping of genes to phenotypes, but assessing the effect of a given genetic perturbation requires evaluation of each single guide RNA (sgRNA) in hundreds of cells to counter stochastic genetic drift and obtain robust results. However, resolution is limited in complex, heterogeneous models, such as organoids or tumors transplanted into mice, because achieving sufficient representation requires impractical scaling. This is due to bottleneck effects and biological heterogeneity of cell populations. Here we introduce CRISPR-StAR, a screening method that uses internal controls generated by activating sgRNAs in only half the progeny of each cell subsequent to re-expansion of the cell clone. Our method overcomes both intrinsic and extrinsic heterogeneity as well as genetic drift in bottlenecks by generating clonal, single-cell-derived intrinsic controls. We use CRISPR-StAR to identify in-vivo-specific genetic dependencies in a genome-wide screen in mouse melanoma. Benchmarking against conventional screening demonstrates the improved data quality provided by this technology.

Major histocompatibility complex class II (MHCII) bound to a peptide antigen mediates interactions between CD4⁺ T cells and antigen-presenting cells. Targeting peptide–MHCII with T cell antigen receptors (TCRs) and TCR-like antibodies has shown promise for autoimmune diseases and microbiome tolerance. To develop a general targeting approach, we introduce targeted recognition of antigen–MHC complex reporter for MHCII (TRACeR-II) for the rapid development of peptide-specific MHCII binders. TRACeR-II binders have a small helical bundle scaffold and use a single loop to recognize peptide–MHCII, which offers versatility and enables structural modeling of the interactions to target MHCII antigens. We demonstrate rapid generation of TRACeR-II binders to multiple molecules with affinities in the low-nanomolar to low-micromolar range, comparable to best-in-class TCRs and antibodies. Through computational protein design, we created specific binding sequences in silico from only the sequence of a severe acute respiratory syndrome coronavirus 2 peptide. TRACeR-II provides a straightforward approach to target antigen–MHCII without relying on combinatorial selection on complementarity-determining region loops.

Identifying highly specific T cell receptors (TCRs) or antibodies against epitopic peptides presented by class I major histocompatibility complex (MHC I) proteins remains a bottleneck in the development of targeted therapeutics. Here, we introduce targeted recognition of antigen–MHC complex reporter for MHC I (TRACeR-I), a generalizable platform for targeting peptides on polymorphic HLA-A*, HLA-B* and HLA-C* allotypes while overcoming the cross-reactivity challenges of TCRs. Our TRACeR–MHC I co-crystal structure reveals a unique antigen recognition mechanism, with TRACeR forming extensive contacts across the entire peptide length to confer single-residue specificity at the accessible positions. We demonstrate rapid screening of TRACeR-I against a panel of disease-relevant HLAs with peptides derived from human viruses (human immunodeficiency virus, Epstein–Barr virus and severe acute respiratory syndrome coronavirus 2), and oncoproteins (Kirsten rat sarcoma virus, paired-like homeobox 2b and New York esophageal squamous cell carcinoma 1). TRACeR-based bispecific T cell engagers and chimeric antigen receptor T cells exhibit on-target killing of tumor cells with high efficacy in the low nanomolar range. Our platform empowers the development of broadly applicable MHC I-targeting molecules for research, diagnostic and therapeutic applications.

The use of adeno-associated viruses (AAVs) as donors for homology-directed repair (HDR)-mediated genome engineering is limited by safety issues, manufacturing constraints and restricted packaging limits. Non-viral targeted genetic knock-ins rely primarily on double-stranded DNA (dsDNA) and linear single-stranded DNA (lssDNA) donors. dsDNA is known to have low efficiency and high cytotoxicity, while lssDNA is challenging for scaled manufacture. In this study, we developed a non-viral genome writing catalyst (GATALYST) system that allows production of circular single-stranded DNAs (cssDNAs) up to approximately 20 kilobases as donor templates for highly efficient precision transgene integration. cssDNA donors enable knock-in efficiency of up to 70% in induced pluripotent stem cells (iPSCs) and improved efficiency in multiple clinically relevant primary immune cell types and at multiple genomic loci implicated for clinical applications with various nuclease editor systems. The high precision and efficiency in chimeric antigen receptor (CAR)-T and natural killer (NK) cells, improved safety, payload flexibility and scalable manufacturability of cssDNA shows potential for future applications of genome engineering.