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The forward genetic screen is a powerful, unbiased method to gain insights into biological processes, yet this approach has infrequently been used in vivo in mammals because of high resource demands. Here, we use in vivo somatic Cas9 mutagenesis to perform an in vivo forward genetic screen in mice to identify regulators of cardiomyocyte (CM) maturation, the coordinated changes in phenotype and gene expression that occur in neonatal CMs. We discover and validate a number of transcriptional regulators of this process. Among these are RNF20 and RNF40, which form a complex that monoubiquitinates H2B on lysine 120. Mechanistic studies indicate that this epigenetic mark controls dynamic changes in gene expression required for CM maturation. These insights into CM maturation will inform efforts in cardiac regenerative medicine. More broadly, our approach will enable unbiased forward genetics across mammalian organ systems. Throughput of in vivo genetic screens is a barrier to efficient application. Here the authors use a high-throughput CRISPR-based in vivo forward genetic screen in mice to identify transcriptional regulators of cardiomyocyte maturation, including the epigenetic modifiers RNF20 and RNF40.

Skeletal muscle, constituting ~40% of body mass, serves as a primary effector for movement and a key metabolic regulator through myokine secretion. Hereditary myopathies, including dystrophinopathies (DMD/BMD), limb–girdle muscular dystrophies (LGMD), and metabolic disorders like Pompe disease, arise from pathogenic mutations in structural, metabolic, or ion channel genes, leading to progressive weakness and multi-organ dysfunction. Gene therapy has emerged as a transformative strategy, leveraging viral and non-viral vectors to deliver therapeutic nucleic acids. Adeno-associated virus (AAV) vectors dominate clinical applications due to their efficient transduction of post-mitotic myofibers and sustained transgene expression. Innovations in AAV engineering, such as capsid modification (chemical conjugation, rational design, directed evolution), self-complementary genomes, and tissue-specific promoters (e.g., MHCK7), enhance muscle tropism while mitigating immunogenicity and off-target effects. Non-viral vectors (liposomes, polymers, exosomes) offer advantages in cargo capacity (delivering full-length dystrophin), biocompatibility, and scalable production but face challenges in transduction efficiency and endosomal escape. Clinically, AAV-based therapies (e.g., Elevidys® for DMD, Zolgensma® for SMA) demonstrate functional improvements, though immune responses and hepatotoxicity remain concerns. Future directions focus on AI-driven vector design, hybrid systems (AAV–exosomes), and standardized manufacturing to achieve “single-dose, lifelong cure” paradigms for muscular disorders.

The rapid improvement of descriptive genomic technologies has fueled a dramatic increase in hypothesized connections between cardiovascular gene expression and phenotypes. However, in vivo testing of these hypotheses has predominantly been relegated to slow, expensive, and linear generation of genetically modified mice. In the study of genomic cis-regulatory elements, generation of mice featuring transgenic reporters or cis-regulatory element knockout remains the standard approach. While the data obtained is of high quality, the approach is insufficient to keep pace with candidate identification and therefore results in biases introduced during the selection of candidates for validation. However, recent advances across a range of disciplines are converging to enable functional genomic assays that can be conducted in a high-throughput manner. Here, we review one such method, massively parallel reporter assays (MPRAs), in which the activities of thousands of candidate genomic regulatory elements are simultaneously assessed via the next-generation sequencing of a barcoded reporter transcript. We discuss best practices for MPRA design and use, with a focus on practical considerations, and review how this emerging technology has been successfully deployed in vivo. Finally, we discuss how MPRAs are likely to evolve and be used in future cardiovascular research.

Precise genome-editing platforms are versatile tools for generating specific, site-directed DNA insertions, deletions, and substitutions. The continuous enhancement of these tools has led to a revolution in the life sciences, which promises to deliver novel therapies for genetic disease. Precise genome-editing can be traced back to the 1950s with the discovery of DNA’s double-helix and, after 70 years of development, has evolved from crude in vitro applications to a wide range of sophisticated capabilities, including in vivo applications. Nonetheless, precise genome-editing faces constraints such as modest efficiency, delivery challenges, and off-target effects. In this review, we explore precise genome-editing, with a focus on introduction of the landmark events in its history, various platforms, delivery systems, and applications. First, we discuss the landmark events in the history of precise genome-editing. Second, we describe the current state of precise genome-editing strategies and explain how these techniques offer unprecedented precision and versatility for modifying the human genome. Third, we introduce the current delivery systems used to deploy precise genome-editing components through DNA, RNA, and RNPs. Finally, we summarize the current applications of precise genome-editing in labeling endogenous genes, screening genetic variants, molecular recording, generating disease models, and gene therapy, including ex vivo therapy and in vivo therapy, and discuss potential future advances.

[...]there is an urgent need to develop better therapeutic strategies for treating inherited CVDs. Inclisiran (ALN-PCSsc), approved for the use in a clinical trial, is a long-acting RNA interference (RNAi) therapeutic agent that inhibits the synthesis of proprotein convertase subtilisin–kexin type 9 (Pcsk9), a target for lowering low-density lipoprotein (LDL) cholesterol to prevent coronary heart disease. [...]providing disease management for such a population is a great challenge. [...]preimplantation genetic testing (PGT) technology has been applied in the prevention of ICD, so that couples with genetic risk of ICD can avoid termination of pregnancy and give birth to healthy children without ICD susceptibility genes. [...]gene therapy is the most powerful and efficient method of managing inherited CVDs, but there is a long way to go to achieve this medical goal.

KRAS mutations are one of the most prevalent genetic alterations in colorectal cancer (CRC). Although directly targeting KRAS still is a challenge in anti-cancer therapies, alternatively inhibiting KRAS related signaling pathways has been approached effectively. Here we firstly reported that MAP kinase, transforming growth factor-β-activated kinase 1 (TAK1), commonly expressed in CRC cell lines and significantly associated with KRAS mutation status. Inhibition of TAK1 by the small molecular inhibitor NG25 could inhibit CRC cells proliferation in vitro and in vivo, especially in KRAS-mutant cells. NG25 induced caspase-dependent apoptosis in KRAS-mutant cells and in orthotopic CRC mouse models by regulating the B-cell lymphoma-2 (Bcl-2) family and the inhibitor of apoptosis protein (IAP) family. Besides inhibiting molecules downstream of MAPK, including ERK, JNK and p38 phosphorylation, NG25 could block NF-κB activation in KRAS-mutant cells. As a target gene of NF-κB, down-regulated XIAP expression may be not only involved in apoptosis induced by NG25, but also reducing the formation of TAK1-XIAP complex that can activate TAK1 downstream signaling pathways, which forms a positive feedback loop to further induce apoptosis in KRAS-mutant CRC cells. Together, these findings indicated that TAK1 is an important kinase for survival of CRCs harboring KRAS mutations, and that NG25 may be a potential therapeutic strategy for KRAS-mutant CRC.

Meiosis is a specialized cell division process that generates gametes for sexual reproduction. However, the factors and underlying mechanisms involving meiotic progression remain largely unknown, especially in humans. Here, it is first showed that HSF5 is associated with human spermatogenesis. Patients with a pathogenic variant of HSF5 are completely infertile. Testicular histologic findings in the patients reveal rare postmeiotic germ cells resulting from meiotic prophase I arrest. Hsf5 knockout (KO) mice confirms that the loss of HSF5 causes defects in meiotic recombination, crossover formation, sex chromosome synapsis, and sex chromosome inactivation (MSCI), which may contribute to spermatocyte arrest at the late pachytene stage. Importantly, spermatogenic arrest can be rescued by compensatory HSF5 adeno‐associated virus injection into KO mouse testes. Mechanistically, integrated analysis of RNA sequencing and chromatin immunoprecipitation sequencing data revealed that HSF5 predominantly binds to promoters of key genes involved in crossover formation (e.g., HFM1, MSH5 and MLH3), synapsis (e.g., SYCP1, SYCP2 and SYCE3), recombination (TEX15), and MSCI (MDC1) and further regulates their transcription during meiotic progression. Taken together, the study demonstrates that HSF5 modulates the transcriptome to ensure meiotic progression in humans and mice. These findings will aid in genetic diagnosis of and potential treatments for male infertility. The findings identify HSF5 as a novel genetic cause for human male infertility associated with meiotic arrest. Moreover, the molecular mechanism of HSF5 is first unambiguously elucidated as a transcriptional regulator orchestrating the transcriptome to ensure meiotic progression in humans and mice. This study sheds light on the genetic diagnosis and potential treatment for male infertility.

Background: Previous studies have reported that polymorphisms in the interleukin-1 gene may be involved in tumorigenesis and tumor progression. Aim: The purpose of the present study was to evaluate whether an insertion/deletion polymorphism, rs3783553, located in the miR-122 target gene interleukin-1α, was associated with the risk of colorectal cancer. Methods: Genomic DNA was extracted from peripheral venous blood of 382 patients with colorectal cancer and 433 controls, and the polymorphism was genotyped using a polymerase chain reaction assay. Results: Significantly decreased colorectal cancer risk was observed to be associated with the interleukin-1α rs3783553 insertion/insertion genotype (P=0.0001; OR=0.41; 95% CI 0.26, 0.65) and the insertion allele (P<0.001; OR=0.68; 95% CI 0.55, 0.83). Stratification analysis based on clinical and pathological features also revealed that the “TTCA” insertion allele of rs3783553 contributes to slow the progression of colorectal cancer. Conclusion: These results suggest that the rs3783553 polymorphism could be a useful genetic marker to predict the size/extent of colorectal cancer.

The ability to efficiently make precise genome edits in somatic tissues will have profound implications for gene therapy and basic science. CRISPR/Cas9 mediated homology-directed repair (HDR) is one approach that is commonly used to achieve precise and efficient editing in cultured cells. Previously, we developed a platform capable of delivering CRISPR/Cas9 gRNAs and donor templates via adeno-associated virus to induce HDR (CASAAV-HDR). We demonstrated that CASAAV-HDR is capable of creating precise genome edits within mouse cardiomyocytes at the neonatal and adult stages. Here, we report several applications of CASAAV-HDR in cardiomyocytes. First, we show the utility of CASAAV-HDR for disease modeling applications by using CASAAV-HDR to create and precisely tag two pathological variants of the titin gene observed in cardiomyopathy patients. We used this approach to monitor the cellular localization of the variants, resulting in mechanistic insights into their pathological functions. Next, we utilized CASAAV-HDR to create another mutation associated with human cardiomyopathy, arginine 14 deletion (R14Del) within the N-terminus of Phospholamban (PLN). We assessed the localization of PLN-R14Del and quantified cardiomyocyte phenotypes associated with cardiomyopathy, including cell morphology, activation of PLN via phosphorylation, and calcium handling. After demonstrating CASAAV-HDR utility for disease modeling we next tested its utility for functional genomics, by targeted genomic insertion of a library of enhancers for a massively parallel reporter assay (MPRA). We show that MPRAs with genomically integrated enhancers are feasible, and can yield superior assay sensitivity compared to tests of the same enhancers in an AAV/episomal context. Collectively, our study showcases multiple applications for precise editing of cardiomyocyte genomes via CASAAV-HDR.