An AsCas12f-based compact genome-editing tool derived by deep mutational scanning and structural analysis.

SpCas9 and AsCas12a are widely utilized as genome-editing tools in human cells. However, their relatively large size poses a limitation for delivery by cargo-size-limited adeno-associated virus (AAV) vectors. The type V-F Cas12f from Acidibacillus sulfuroxidans is exceptionally compact (422 amino acids) and has been harnessed as a compact genome-editing tool.

PAM-flexible Cas9-mediated base editing of a hemophilia B mutation in induced pluripotent stem cells.

Background: Base editing via CRISPR-Cas9 has garnered attention as a method for correcting disease-specific mutations without causing double-strand breaks, thereby avoiding large deletions and translocations in the host chromosome. However, its reliance on the protospacer adjacent motif (PAM) can limit its use. We aimed to restore a disease mutation in a patient with severe hemophilia B using base editing with SpCas9-NG, a modified Cas9 with the board PAM flexibility.

Cardiac progenitors instruct second heart field fate through Wnts.

The heart develops in a synchronized sequence of proliferation and differentiation of cardiac progenitor cells (CPCs) from two anatomically distinct pools of cells, the first heart field (FHF) and second heart field (SHF). Congenital heart defects arise upon dysregulation of these processes, many of which are restricted to derivatives of the FHF or SHF. Of the conserved set of signaling pathways that regulate development, the Wnt signaling pathway has long been known for its importance in SHF development.

Sarcomere maturation: function acquisition, molecular mechanism, and interplay with other organelles.

During postnatal cardiac development, cardiomyocytes mature and turn into adult ones. Hence, all cellular properties, including morphology, structure, physiology and metabolism, are changed. One of the most important aspects is the contractile apparatus, of which the minimum unit is known as a sarcomere.

Cross-Organ Transcriptomic Comparison Reveals Universal Factors During Maturation.

Various cell types can be derived from stem cells. However, these cells are immature and do not match their adult counterparts in functional capabilities, limiting their use in disease modeling and cell therapies. Thus, it is crucial to understand the mechanisms of maturation in vivo.

Protective roles of MITOL against myocardial senescence and ischemic injury partly via Drp1 regulation.

Abnormal mitochondrial fragmentation by dynamin-related protein1 (Drp1) is associated with the progression of aging-associated heart diseases, including heart failure and myocardial infarction (MI). Here, we report a protective role of outer mitochondrial membrane (OMM)-localized E3 ubiquitin ligase MITOL/MARCH5 against cardiac senescence and MI, partly through Drp1 clearance by OMM-associated degradation (OMMAD). Persistent Drp1 accumulation in cardiomyocyte-specific MITOL conditional-knockout mice induced mitochondrial fragmentation and dysfunction, including reduced ATP production and increased ROS generation, ultimately leading to myocardial senescence and chronic heart failure.

Prolonged Myocardial Regenerative Capacity in Neonatal Opossum.

Background: Early neonates of both large and small mammals are able to regenerate the myocardium through cardiomyocyte proliferation for only a short period after birth. This myocardial regenerative capacity declines in parallel with withdrawal of cardiomyocytes from the cell cycle in the first few postnatal days. No mammalian species examined to date has been found capable of a meaningful regenerative response to myocardial injury later than 1 week after birth.

Rapid manipulation of mitochondrial morphology in a living cell with iCMM.

Engineered synthetic biomolecular devices that integrate elaborate information processing and precisely regulate living cell behavior have potential in various applications. Although devices that directly regulate key biomolecules constituting inherent biological systems exist, no devices have been developed to control intracellular membrane architecture, contributing to the spatiotemporal functions of these biomolecules. This study developed a synthetic biomolecular device, termed inducible counter mitochondrial morphology (iCMM), to manipulate mitochondrial morphology, an emerging informative property for understanding physiopathological cellular behaviors, on a minute timescale by using a chemically inducible dimerization system.

Sympathetic Neurons Regulate Cardiomyocyte Maturation in Culture.

Embryos devoid of autonomic innervation suffer sudden cardiac death. However, whether autonomic neurons have a role in heart development is poorly understood. To investigate if sympathetic neurons impact cardiomyocyte maturation, we co-cultured phenotypically immature cardiomyocytes derived from human induced pluripotent stem cells with mouse sympathetic ganglion neurons.

Disease Modeling of Mitochondrial Cardiomyopathy Using Patient-Specific Induced Pluripotent Stem Cells.

Mitochondrial cardiomyopathy (MCM) is characterized as an oxidative phosphorylation disorder of the heart. More than 100 genetic variants in nuclear or mitochondrial DNA have been associated with MCM. However, the underlying molecular mechanisms linking genetic variants to MCM are not fully understood due to the lack of appropriate cellular and animal models.

Noncanonical Notch signals have opposing roles during cardiac development.

The Notch pathway is an ancient intercellular signaling system with crucial roles in numerous cell-fate decision processes across species. While the canonical pathway is activated by ligand-induced cleavage and nuclear localization of membrane-bound Notch, Notch can also exert its activity in a ligand/transcription-independent fashion, which is conserved in Drosophila, Xenopus, and mammals. However, the noncanonical role remains poorly understood in in vivo processes.

Generation of Efficient Knock-in Mouse and Human Pluripotent Stem Cells Using CRISPR-Cas9.

A knock-in can generate fluorescent or Cre-reporter under the control of an endogenous promoter. It also generates knock-out or tagged-protein with fluorescent protein and short tags for tracking and purification. Recent advances in genome editing with clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated protein 9 (Cas9) significantly increased the efficiencies of making knock-in cells.

Decreased Lamin B1 Levels Affect Gene Positioning and Expression in Postmitotic Neurons.

Gene expression programs and concomitant chromatin regulation change dramatically during the maturation of postmitotic neurons. Subnuclear positioning of gene loci is relevant to transcriptional regulation. However, little is known about subnuclear genome positioning in neuronal maturation.

Sarcomere Shortening of Pluripotent Stem Cell-Derived Cardiomyocytes using Fluorescent-Tagged Sarcomere Proteins.

Pluripotent stem cell-derived cardiomyocytes (PSC-CMs) can be produced from both embryonic and induced pluripotent stem (ES/iPS) cells. These cells provide promising sources for cardiac disease modeling. For cardiomyopathies, sarcomere shortening is one of the standard physiological assessments that are used with adult cardiomyocytes to examine their disease phenotypes.

PGC1/PPAR drive cardiomyocyte maturation at single cell level via YAP1 and SF3B2.

Cardiomyocytes undergo significant structural and functional changes after birth, and these fundamental processes are essential for the heart to pump blood to the growing body. However, due to the challenges of isolating single postnatal/adult myocytes, how individual newborn cardiomyocytes acquire multiple aspects of the mature phenotype remains poorly understood. Here we implement large-particle sorting and analyze single myocytes from neonatal to adult hearts.

Non-viral genome-editing in mouse bona fide hematopoietic stem cells with CRISPR/Cas9.

We conducted two lines of genome-editing experiments of mouse hematopoietic stem cells (HSCs) with the clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated protein 9 (Cas9). First, to evaluate the genome-editing efficiency in mouse bona fide HSCs, we knocked out integrin alpha 2b () with Cas9 ribonucleoprotein (Cas9/RNP) and performed serial transplantation in mice. The knockout efficiency was estimated at approximately 15%.

Fetal sheep support the development of hematopoietic cells in vivo from human induced pluripotent stem cells.

We report that a sheep fetal liver provides a microenvironment for generating hematopoietic cells with long-term engrafting capacity and multilineage differentiation potential from human induced pluripotent stem cell (iPSC)-derived hemogenic endothelial cells (HEs). Despite the promise of iPSCs for making any cell types, generating hematopoietic stem and progenitor cells (HSPCs) is still a challenge. We hypothesized that the hematopoietic microenvironment, which exists in fetal liver but is lacking in vitro, turns iPSC-HEs into HSPCs.

Comparative Transcriptome Landscape of Mouse and Human Hearts.

Transcriptome landscape of organs from mice and humans offers perspectives on the process of how organs develop and the similarity and diversity in each organ between the species. Among multi-species and multi-organ dataset, which was previously generated, we focused on the mouse and human dataset and performed a reanalysis to provide a more specific perspective on the maturation of human cardiomyocytes. First, we examined how organs diversify their transcriptome during development across and within two species.

Use of Freeze-thawed Embryos for High-efficiency Production of Genetically Modified Mice.

The use of genetically modified (GM) mice has become crucial for understanding gene function and deciphering the underlying mechanisms of human diseases. The CRISPR/Cas9 system allows researchers to modify the genome with unprecedented efficiency, fidelity, and simplicity. Harnessing this technology, researchers are seeking a rapid, efficient, and easy protocol for generating GM mice.

A Brief Review of Current Maturation Methods for Human Induced Pluripotent Stem Cells-Derived Cardiomyocytes.

Cardiovascular diseases are the leading cause of death worldwide. Therefore, the discovery of induced pluripotent stem cells (iPSCs) and the subsequent generation of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) was a pivotal point in regenerative medicine and cardiovascular research. They constituted an appealing tool for replacing dead and dysfunctional cardiac tissue, screening cardiac drugs and toxins, and studying inherited cardiac diseases.

A Novel Fluorescent Reporter System Identifies Laminin-511/521 as Potent Regulators of Cardiomyocyte Maturation.

Pluripotent stem cell-derived cardiomyocytes (PSC-CMs) hold great promise for disease modeling and drug discovery. However, PSC-CMs exhibit immature phenotypes in culture, and the lack of maturity limits their broad applications. While physical and functional analyses are generally used to determine the status of cardiomyocyte maturation, they could be time-consuming and often present challenges in comparing maturation-enhancing strategies.

Generation of novel Il2rg-knockout mice with clustered regularly interspaced short palindromic repeats (CRISPR) and Cas9.

X-linked severe combined immunodeficiency (X-SCID) is an inherited genetic disorder. A majority of X-SCID subjects carries point mutations in the Interleukin-2 receptor gamma chain (IL2RG) gene. In contrast, Il2rg-knockout mice recapitulating X-SCID phenotype lack a large part of Il2rg instead of point mutations.

Rapid and high-efficient generation of mutant mice using freeze-thawed embryos of the C57BL/6J strain.

Background: The CRISPR/Cas9 technique has undergone many modifications to decrease the effort and shorten the time needed for efficient production of mutant mice. The use of fresh embryos consumes time and effort during oocytes preparation and fertilization before every experiment, and freeze-thawed embryos overcome this limitation. However, cryopreservation of 1-cell embryos is challenging.

Tbx6 Induces Nascent Mesoderm from Pluripotent Stem Cells and Temporally Controls Cardiac versus Somite Lineage Diversification.

The mesoderm arises from pluripotent epiblasts and differentiates into multiple lineages; however, the underlying molecular mechanisms are unclear. Tbx6 is enriched in the paraxial mesoderm and is implicated in somite formation, but its function in other mesoderms remains elusive. Here, using direct reprogramming-based screening, single-cell RNA-seq in mouse embryos, and directed cardiac differentiation in pluripotent stem cells (PSCs), we demonstrated that Tbx6 induces nascent mesoderm from PSCs and determines cardiovascular and somite lineage specification via its temporal expression.