Fluorescent Reporters Distinguish Stem Cell Colony Subtypes During Somatic Cell Reprogramming

Reporter Alleles in hiPSCs: Visual Cues on Development and Disease

Reporter alleles are essential for advancing research with human induced pluripotent stem cells (hiPSCs), notably in developmental biology and disease modeling. This study investigates the state-of-the-art gene-editing techniques tailored for generating reporter alleles in hiPSCs, emphasizing their effectiveness in investigating cellular dynamics and disease mechanisms. Various methodologies, including the application of CRISPR/Cas9 technology, are discussed for accurately integrating reporter genes into the specific genomic loci. The synthesis of findings from the studies utilizing these reporter alleles reveals insights into developmental processes, genetic disorder modeling, and therapeutic screening, consolidating the existing knowledge. These hiPSC-derived models demonstrate remarkable versatility in replicating human diseases and evaluating drug efficacy, thereby accelerating translational research. Furthermore, this review addresses challenges and future directions in refining the reporter allele design and application to bolster their reliability and relevance in biomedical research. Overall, this investigation offers a comprehensive perspective on the methodologies, applications, and implications of reporter alleles in hiPSC-based studies, underscoring their essential role in advancing both fundamental scientific understanding and clinical practice.

The occurrence and development of induced pluripotent stem cells

The ectopic expression of four transcription factors, Oct3/4, Sox2, Klf4, and c-Myc (OSKM), known as "Yamanaka factors," can reprogram or stimulate the production of induced pluripotent stem cells (iPSCs). Although OSKM is still the gold standard, there are multiple ways to reprogram cells into iPSCs. In recent years, significant progress has been made in improving the efficiency of this technology. Ten years after the first report was published, human pluripotent stem cells have gradually been applied in clinical settings, including disease modeling, cell therapy, new drug development, and cell derivation. Here, we provide a review of the discovery of iPSCs and their applications in disease and development.

OCT4 is expressed in extraembryonic endoderm stem (XEN) cell progenitors during somatic cell reprogramming

During development, progenitors of embryonic stem (ES) and extraembryonic endoderm stem (XEN) cells are concomitantly specified within the inner cell mass (ICM) of the mouse blastocyst. Similarly, XEN cells are induced (iXEN cells) alongside induced pluripotent stem (iPS) cells following overexpression of Oct4, Sox2, Klf4 and Myc (OSKM) during somatic cell reprogramming. It is unclear how or why this cocktail produces both stem cell types, but OCT4 has been associated with non-pluripotent outcomes. In this report, we show that, during OSKM reprogramming, many individual Oct4-GFP-expressing cells are fated to become iXEN cells. Interestingly, SKM alone was also sufficient to induce iXEN cell formation, likely via activation of endogenous Oct4. These observations indicate that iXEN cell formation is not strictly an artifact of Oct4 overexpression. Moreover, our results suggest that a pathway to XEN may be an integral feature of establishing pluripotency during reprogramming, as in early embryo development.