CMN Weekly (24 March 2023) - Your Weekly CRISPR Medicine News

Top picks

• In vivo prime editing has successfully prevented vision loss in mice with inherited retinitis pigmentosa. Fourteen days postnatally, mice carrying a mutated phosphodiesterase 6b (PDE6b) gene were injected subretinally with AAV vectors carrying split PE^SpRY and pegRNA designed to correct the single C->T mutation. After injection, PDE enzyme activity rose from virtually zero to lasting levels around 80% of wild-type. Various behavioural tests confirmed that, in contrast to untreated mice, prime-edited mice did not develop blindness and retained their vision even into old age. Read more about the achievement and its perspectives in this insight: Eye on genome editing.
• Researchers in China present a logic-gated CRISPR-Cas13d-based nanoprodrug (URL) for orthogonal photomodulation of gene editing and prodrug release for enhanced cancer therapy. URL is the combined encapsulation in nanoparticles of a green light-activatable platinum(IV) chemotherapy prodrug and a UV light-activatable Cas13d gene editing tool. In vivo studies demonstrated that URL can deliver an ultimate chemo-photodynamic therapeutic performance in efficiently eradicating primary tumours and preventing further liver metastasis.

Research

• Researchers in The Netherlands have demonstrated the precise homology-directed installation of large genomic edits in human cells with cleaving and nicking high-specificity Cas9 variants. The method utilises in trans paired nicking (ITPN) that involves tandem single-strand DNA breaks at target loci and exogenous donor constructs by CRISPR-Cas9 nickases and fosters seamless and scarless genome editing.
• Researchers in Israel show, for the first time, that CRISPR-Cas9-based disruption of the TLR4-gene reduces pro-inflammatory polarisation of hMSCs and improves infarct healing and remodelling in mice. The results provide a new approach to improving the outcomes of cell therapy for cardiovascular diseases.
• Researchers in China describe a potential gene-editing therapy for Charcot-Marie-Tooth disease (CMT) severely affects patient activity and may cause disability. iPSCs from patients with the c.880G>A heterozygous nucleotide mutation in the GARS gene. Subsequently, CRISPR-Cas9 technology was used to repair the mutated gene sites at the iPSC level.
• Researchers in Korea have developed a split-tracrRNA system for improved scalability of tracrRNA synthesis. The split-tracrRNA, tracrRNA(41 + 23), is produced by nicking in the stem-loop 2 of the original tracrRNA(67), and it showed gene editing efficiency and specificity comparable to those of tracrRNA(67).

Industry

• Intellia Therapeutics announced that the FDA has granted Regenerative Medicine Advanced Therapy (RMAT) designation to NTLA-2002 for treating hereditary angioedema (HAE). NTLA-2002 is an in vivo CRISPR-based investigational therapy designed to inactivate the target gene, kallikrein B1 (KLKB1), to prevent life-threatening swelling attacks in people with HAE potentially.
• Graphite Bio reports recent business updates and fiscal year 2022 financial results. The year ended with a cash position of $286 million, expenses (R&D, general and administrative) of $105 million and a net loss of $101 million. In February, the company announced its decision to discontinue the development of nulabeglogene autogedtemcel (nula-cel) for sickle cell disease, which was in phase 1/2 clinical trial.
• HuidaGene Therapeutics has presented a novel min-dCas13X-mediated RNA adenine base-editing (mxABE) platform today at the 2023 Muscular Dystrophy Association Clinical & Scientific Conference. The mxABE platform efficiently corrects nonsense mutations in the DMD gene, robustly restores dystrophin expression and muscle function, and continuously sustains both dystrophin expression and muscle function for six months after one injection in a humanised DMD mouse model.

Detection

• Researchers in Mexico demonstrate how multiplex gRNAs can synergically enhance the detection of SARS-CoV-2 by CRISPR-Cas12a. Using 2-3 gRNAs in parallel resulted in a 4.5 × faster cleaving rate of the probe and increased sensitivity compared to using individual gRNAs.
• Canadian researchers demonstrate a system, FACTOR, a CRISPR-based diagnostic for sensing any nucleic acid of interest. FACTOR combines FACT (a CRISPR-based nucleic acid barcoding technology compatible with Cas12a and Cas13a) and RePAIR (a reprogrammable pairing system).
• Chinese researchers have developed a nucleic acid detection platform for identifying methicillin-resistant Staphylococcus aureus (MRSA) using CRISPR-Cas12a and sgRNAs, specifically targeting the thermonuclease (nuc) and mecA genes. The fast and precise system can detect down to 4 × 10³ fg/μL of genomic DNA in 80 min (based on fluorescence readout) or 85 min (based on strip readout).
• Researchers in China propose a CRISPR-Cas-Driven Single Micromotor (Cas-DSM) that can detect nucleic acid targets at a single-molecule level with high specificity. The Cas-DSM is a reliable and practical method for quantitatively detecting DNA/RNA in various complex clinical samples and in individual cells without any preamplification processes.
• Chinese researchers describe a chemical additive-enhanced single-step accurate CRISPR/Cas13 testing system for field-deployable ultrasensitive detection and genotyping of SARS-CoV-2 variants of concern. The genotyping results for 40 clinical samples were in 100% concordance with the standard method.

Reviews

• Phage against the machine: Discovery and mechanism of type V anti-CRISPRs. This review discusses the discovery, mechanism, and future areas for exploring anti-CRISPR proteins that phages have evolved to prevent targeting.
• Periodontal disease pathogens, pathogenesis, and therapeutics: The CRISPR-Cas effect. This review article describes the CRISPR-Cas systems in the periodontal dysbiotic microbial communities, their role in the virulence of periodontal pathogens, and their potential role in understanding the pathogenesis of periodontitis and the treatment of periodontal disease.
• CRISPR-Cas-based aptasensor as an innovative sensing approaches for food safety analysis: Recent progresses and new horizons. This study explores some of the most recent progress in the CRISPR-Cas-mediated aptasensors for detecting food risk factors, including veterinary drugs, pesticide residues, pathogens, mycotoxins, heavy metals, illegal additives, food additives, and other contaminants.
• CRISPR-Cas systems for the detection of nucleic acid and non-nucleic acid targets. This review summarises the principles and characteristics of various CRISPR-Cas systems, their use in detecting nucleic and non-nucleic acid targets, and the prospects and challenges of their applications in biosensing.
• CRISPR-Cas assisted diagnostics: A broad application biosensing approach. This review aims to describe the latest trends in the design of CRISPR-Cas biosensing technologies to highlight the insights of their advantages better and to point out the limitations that still need to be overcome for their future market entry as medical diagnostics.

Meetings

• CRISPR as a cancer and regenerative medicine research tool is an international two-day symposium at the Karolinska Institutet on 25-28 May. It brings together leading international experts in CRISPR technology and CRISPR applications in basic research in cancer and regenerative medicine.

Editor note: This article was published on 24th March 2023. In the original text, it was incorrectly stated in the Research section that: 'Chinese researchers have developed a split-tracrRNA system for improved scalability of tracrRNA synthesis. The split-tracrRNA, tracrRNA(41 + 23).....' The researchers behind that study were in Korea, and the text was updated on 27th March 2023 to reflect this.