CMN Weekly (26 July 2024) - Your Weekly CRISPR Medicine News

Top picks

• CRISPR-Cas has been used to engineer human B cells to produce heavy-chain-only antibodies (HCAbs), mimicking camelid antibodies. The editing strategy inserts antigen-recognition domains (ARDs) into the IgG1 locus, preserving B cell receptor (BCR) functions and antibody secretion. Engineered B cells exhibited antigen-specific responses and memory cell formation in a tonsil organoid model, demonstrating the potential for customizable antibody therapies.
• Researchers have developed CasPlus, a CRISPR-Cas9 variant with T4 DNA polymerase, to improve gene editing safety and precision. CasPlus reduces on-target large deletions and chromosomal translocations, increasing precise 1- to 2-base-pair insertions. It efficiently corrected DMD mutations, restoring dystrophin expression, and showed enhanced safety in mouse germline editing and primary human T cells, offering a safer, more efficient gene editing tool.

Research

• CDC7 inhibition, achieved via CRISPR-Cas9 and the inhibitor simurosertib, impairs neuroendocrine transformation (NET) in lung and prostate tumours. This process involves MYC degradation, which is critical for NE transformation. Consequently, targeted CDC7 inhibition not only extends the effectiveness of existing therapies but also presents a promising strategy to manage high-risk patients by delaying or preventing the histological transformation associated with poor prognosis.
• American researchers have presented click editing, a new method for precise, versatile genome modifications without double-strand breaks. Click editing leverages the unique properties of DNA-dependent polymerases, RNA-programmable nickases, and minimally or unmodified nucleic acid templates called clkDNAs to target the desired edits.
• Researchers have discovered that miR-203, an epigenetically regulated microRNA, is crucial for trigeminal ganglion formation in chick embryos. Using CRISPR-Cas9 and miR-203 sponging, they showed that neural crest cells secrete miR-203, which is then incorporated into placode cells via extracellular vesicles. Overexpression of miR-203 led to ectopic coalescence and increased ganglion size, highlighting intercellular communication’s role in ganglion development.
• By precisely deleting the CD5 gene, which inhibits T-cell activation, American researchers have created chimeric antigen receptor (CAR) T-cells with superior antitumor activity, expansion, and persistence. This CRISPR-based gene editing was pivotal in boosting the therapeutic performance against various cancer models, including T-cell lymphomas, acute lymphoblastic leukaemia, B-cell malignancies, and solid tumours.
• French researchers have used CRISPR-Cas9 to reactivate fetal haemoglobin (HbF) to treat sickle cell disease (SCD). Targeting LRF repressor sites in γ-globin promoters, they achieved robust HbF synthesis in healthy donor and SCD-derived HSPCs. While maintaining differentiation, SCD cells showed reduced engraftment and a myeloid bias. Increased off-target activity and upregulation of DNA damage and inflammatory genes were observed, highlighting the need for thorough safety studies.
• Researchers have developed a novel strategy to treat spinal muscular atrophy (SMA) by combining gene supplementation with CRISPR genome editing. The study employs a CRISPR-Cas9-based homology-independent targeted integration (HITI) strategy to correct the SMA mutation in mice in conjunction with Smn1 cDNA supplementation. HITI, effective in both dividing and non-dividing cells, uses non-homologous end joining (NHEJ) to integrate transgenes, ensuring stable gene correction without the need for homologous recombination.
• Chinese researchers have demonstrated the feasibility of using RNA molecules as repair templates for homologous recombination in mammalian cells. By fusing RNA templates to the 3´-end of sgRNA, they created a single RNA molecule to target gene editing. This approach showed successful gene editing and highlighted that longer homologous arms and inducing an R-loop near the double-strand break (DSB) enhance repair efficiency.

Industry

• Cellectis has announced that the FDA has granted Orphan Drug (ODD) and Rare Pediatric Disease Designation (RPDD) Status to the UCART22 product candidate for the treatment of Acute Lymphoblastic Leukemia (ALL). UCART22 is a TALEN-engineered CD22-targeting allogeneic CAR T-cell therapeutic candidate currently being evaluated in the BALLI-0 Phase 1/2 trial.

CRISPR screens

• Using a CRISPR-Cas9-based in vivo genetic screen, TFDP1 was identified as crucial for hematopoietic stem and progenitor cell (HSPC) proliferation and post-transplant haematopoiesis. TFDP1 partners with E2F4, which is necessary for HSPC proliferation. Deletion of TFDP1 downregulates cell cycle-associated genes, half of which are direct TFDP1/E2F4 targets, highlighting their role in hematopoietic development.

Detection

• A new CreDiT (CRISPR Enhanced Digital Testing) platform enables rapid, on-site nucleic acid detection crucial for cervical cancer care, particularly in low- and middle-income countries. CreDiT integrates a one-pot CRISPR strategy for simultaneous amplification and signal analysis with robust fluorescent detection technology. It delivers sensitive HPV DNA detection in under 35 minutes, accurately identifying HPV types in clinical specimens.
• Researchers have developed a one-tube assay combining RT-RPA and CRISPR-Cas12a to detect human metapneumovirus (HMPV). By targeting the nucleoprotein gene, this assay achieves rapid visual detection at one copy/μL in 30 minutes, showing 98.53% concordance with quantitative RT-PCR. This method, which avoids cross-reactivity with other respiratory pathogens, offers a simplified and efficient platform for early HMPV detection.

Reviews

• Coding, or non-coding, that is the question. This review, among other topics, highlights the use of CRISPR-Cas gene editing technology to surgically alter miRNA response elements (MREs) in mRNAs, disrupting their competing endogenous RNA (ceRNA) function.
• Adenoviral Vector System: A Comprehensive Overview of Constructions, Therapeutic Applications and Host Responses. This review highlights the evolution of adenoviral vectors for gene therapy and vaccine development, emphasizing advancements in CRISPR-Cas9 and other technologies to enhance efficacy and safety by addressing challenges such as pre-existing immunity and developing vectors from rare adenovirus types and non-human species.
• Gene drives: an alternative approach to malaria control? This review discusses the use and progress of gene drives for vector control, particularly malaria. It also addresses the limitations and ethics of using gene drives for mosquito control.
• CRISPR/Cas9 technology in the modeling of and treatment of mucopolysaccharidosis. This review concentrates on the application of this technique in the treatment of MPS, particularly MPS I, and the modelling of disease-causing mutations.

Perspectives

• Researchers highlight the security risks of genome editing despite its medical benefits. They call for an integrated approach to regulate and prevent misuse, noting insufficient focus on dual-use concerns in the WHO’s 2021 framework. Proposed steps include 1) integrating genome editing into security strategies, 2) enhancing international dialogue, 3) creating a global verification mechanism, and 4) tracking genome editing technologies.
• A perspective in Nature Structural & Molecular Biology explores the structural and biochemical intricacies that govern the functionality of CRISPR–Cas technologies. The author emphasizes the need for a nuanced mechanistic understanding to overcome current limitations and pave the way for safer and more effective genome-editing applications in medicine and research. The author argues that uncovering the rate-limiting biochemical and enzymatic mechanisms of genome-editing technologies will broaden existing horizons and lead to the development of new tools to modify the genome.

News from CRISPR Medicine News

• On Monday, we brought a short interview with Benjamin Kleinstiver from Massachusetts General Hospital and Harvard Medical School. He presented click editing, a new method for precise, versatile genome modifications that leverages the unique properties of DNA-dependent polymerases and RNA-programmable nickases and avoids the risks associated with double-strand breaks.