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Transgenic technology for mosquitoes is now more than two decades old, and a wide array of control sequences have been described for regulating gene expression in various life stages or specific tissues. Despite this, comparatively little attention has been paid to the development and validation of other transgene-regulating elements, especially 3ʹ-untranslated regions (3ʹUTRs). As a consequence, the same regulatory sequences are often used multiple times in a single transgene array, potentially leading to instability of transgenic effector genes. To increase the repertoire of characterized 3ʹUTRs available for genetics-based mosquito control, we generated fifteen synthetic sequences based on the base composition of the widely used SV40 3ʹUTR sequence, and tested their ability to contribute to the expression of reporter genes EGFP or luciferase. Transient transfection in mosquito cells identified nine candidate 3ʹUTRs that conferred moderate to strong gene expression. Two of these were engineered into the mosquito genome through CRISPR/Cas9-mediated site-specific insertion and compared to the original SV40 3ʹUTR. Both synthetic 3ʹUTRs were shown to successfully promote transgene expression in all mosquito life stages (larva, pupa and adults), similar to the SV40 3ʹUTR, albeit with differences in intensity. Thus, the synthetic 3ʹUTR elements described here are suitable for regulating transgene expression in Ae. aegypti, and provide valuable alternatives in the design of multi-gene cassettes. Additionally, the synthetic-scramble approach we validate here could be used to generate additional functional 3ʹUTR elements in this or other organisms.

Background: CB-012 is an allogeneic anti-CLL-1 CAR-T cell therapy in development for evaluation in relapsed or refractory acute myeloid leukemia (r/r AML). CB-012 is engineered with a next-generation CRISPR genome-editing technology to leverage both checkpoint disruption and immune cloaking to enhance persistence of CAR-T cell antitumor activity. Methods: Caribou’s CRISPR hybrid RNA-DNA (chRDNA) guides in combination with Cas12a were used to make five edits in the manufacture of CB-012. A fully human anti-CLL-1 CAR transgene was site-specifically inserted into the TRAC gene, thereby eliminating TCR expression to prevent graft-versus-host disease. A B2M-HLA-E fusion transgene was inserted into the native B2M gene, preventing expression of all HLA class I antigens except HLA-E, to blunt both T and NK cell-mediated allograft rejection of the CAR-T cells. A knockout of the PDCD1 gene prevented PD-1 receptor expression and thus PD-L1 ligand binding, thereby prolonging antitumor activity. These multiplex genome-editing strategies were designed to enhance persistence of CB-012 antitumor activity and potentially achieve durable therapeutic responses. Results: CB-012 CAR-T cells express a potent, fully human anti-CLL-1 scFv CAR construct and demonstrate CLL-1-dependent cytotoxicity, proliferation, and cytokine secretion in vitro using AML cell line models. In AML xenografts, robust tumor control and prolongation of survival was observed following a single dose of CB-012. In serial rechallenge assays, CB-012 cells maintained increased cytolytic potential when repeatedly challenged with CLL-1-expressing tumor cells compared to similarly engineered CAR-T cells without a PD-1 knockout, demonstrating a functional benefit of PD-1 abrogation. This advantage was modelled in vivo, conferring superior prolongation of survival with CB-012 treatment compared to similarly engineered CAR-T cells without a PD-1 knockout. Additionally, CB-012 cells expressing the B2M-HLA-E fusion demonstrated resistance to NK cell-mediated cytotoxicity in vitro. Conclusions: CLL-1 is a compelling therapeutic target as it is highly expressed on AML tumor cells and leukemic stem cells, but not expressed on hematopoietic stem cells. It has also been established as a target in human proof-of-concept studies. CB-012 demonstrated potent and specific CLL-1-targeted cytolytic activity, and the genome-editing strategy employed to manufacture and armor CB-012 conferred a functional advantage in the context of the potentially immunosuppressive tumor microenvironment associated with r/r AML. Citation Format: Elizabeth Garner, Erin Kelly, Sai Namburi, Cian Colgan, Tristan Fowler, Devin Mutha, Art Aviles, Morena Stanaway, Raymond Guo, Zili An, Emilie Degagne, George Kwong, Leslie Edwards, Emma Jakes, McKay Shaw, Benjamin Schilling, Jeremy Huynh, Ricky Luu, Max Sidorov, Rhonda Mousali, Mikk Otsmaa, Justin Skoble, Steven Kanner. CB-012, an allogeneic anti-CLL-1 CAR-T cell therapy engineered with next-generation CRISPR technology to resist both the immunosuppressive tumor microenvironment and immune cell-mediated rejection, for patients with relapsed or refractory acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3201.

Mosquito gene editing has become routine in several laboratories with the establishment of systems such as transcription-activator-like effector nucleases (TALENs), zinc-finger nucleases (ZFNs), and homing endonucleases (HEs). More recently, clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology has offered an easier and cheaper alternative for precision genome engineering. Following nuclease action, DNA repair pathways will fix the broken DNA ends, often introducing indels. These out-of-frame mutations are then used for understanding gene function in the target organisms. A drawback, however, is that mutant individuals carry no dominant marker, making identification and tracking of mutant alleles challenging, especially at scales needed for many experiments. High-resolution melt analysis (HRMA) is a simple method to identify variations in nucleic acid sequences and utilizes PCR melting curves to detect such variations. This post-PCR analysis method uses fluorescent double-stranded DNA-binding dyes with instrumentation that has temperature ramp control data capture capability and is easily scaled to 96-well plate formats. Described here is a simple workflow using HRMA for the rapid detection of CRISPR/Cas9-induced indels and the establishment of mutant lines in the mosquito Ae. aegypti. Critically, all steps can be performed with a small amount of leg tissue and do not require sacrificing the organism, allowing genetic crosses or phenotyping assays to be performed after genotyping.

Genetics-based pest management processes, including the sterile insect technique, are an effective method for the control of some pest insects. However, current SIT methods are not directly transferable to many important pest insect species due to the lack of genetic sexing strains. Genome editing is revolutionizing the way we conduct genetics in insects, including in Tribolium castaneum, an important genetic model and agricultural pest. We identified orthologues of β2Tubulin, Rad50-ATPase and enolase in T. castaneum. Using RT-PCR, we confirmed that these genes are predominantly expressed in the testis. PiggyBac-based transformation of T. castaneum cis-regulatory regions derived from Tc-β2t, Tc-rad50 or Tc-eno resulted in EGFP expression specifically in the T. castaneum testis. Additionally, we determined that each of these regulatory regions regulates EGFP expression in different cell types of the male gonad. Cis-regulatory regions from Tc-β2t produced EGFP expression throughout spermatogenesis and also in mature sperms; Tc-rad50 resulted in expression only in the haploid spermatid, while Tc-eno expressed EGFP in late spermatogenesis. In summary, the regulatory cis-regions characterized in this study are not only suited to study male gonadal function but could be used for development of transgenic sexing strains that produce one sex in pest control strategies.

Aedes aegypti is a critical vector for transmitting Zika, dengue, chikungunya, and yellow fever viruses to humans. Genetic strategies to limit mosquito survival based upon sex distortion or disruption of development may be valuable new tools to control Ae. aegypti populations. We identified six genes with expression limited to pupal development ; osi8 and osi11 (Osiris protein family), CPRs and CPF (cuticle protein family), and stretchin (a muscle protein). Heritable CRISPR/Cas9-mediated gene knockout of these genes did not reveal any defects in pupal development. However, stretchin-null mutations (strnΔ35/Δ41) resulted in flightless mosquitoes with an abnormal open wing posture. The inability of adult strnΔ35/Δ41 mosquitoes to fly restricted their escape from aquatic rearing media following eclosion , and substantially reduced adult survival rates. Transgenic strains which contain the EGFP marker gene under the control of strn regulatory regions (0.8 kb, 1.4 kb, and 2.2 kb upstream, respectively), revealed the gene expression pattern of strn in muscle-like tissues in the thorax during late morphogenesis from L 4 larvae to young adults. We demonstrated that Ae. aegypti pupae-specific strn is critical for adult mosquito flight capability and a key late-acting lethal target for mosquito-borne disease control.