A Tendon-Specific Double Reporter Transgenic Mouse Enables Tracking Cell Lineage and Functions Alteration In Vitro and In Vivo

We generated and characterized a transgenic mouse line with the tendon-specific expression of a double fluorescent reporter system, which will fulfill an unmet need for animal models to support real-time monitoring cell behaviors during tendon development, growth, and repair in vitro and in vivo. The mScarlet red fluorescent protein is driven by the Scleraxis (Scx) promoter to report the cell lineage alteration. The blue fluorescent protein reporter is expressed under the control of the 3.6kb Collagen Type I Alpha 1 Chain (Col1a1) proximal promoter. In this promoter, the existence of two promoter regions named tendon-specific cis-acting elements (TSE1, TSE2) ensure the specific expression of blue fluorescent protein (BFP) in tendon tissue. Collagen I is a crucial marker for tendon regeneration that is a major component of healthy tendons. Thus, the alteration of function during tendon repair can be estimated by BFP expression. After mechanical stimulation, the expression of mScarlet and BFP increased in adipose-derived mesenchymal stem cells (ADMSCs) from our transgenic mouse line, and there was a rising trend on tendon key markers. These results suggest that our tendon-specific double reporter system is a novel model used to study cell re-differentiation and extracellular matrix alteration in vitro and in vivo.

Gene editing in bacteria by CRISPR-Cas9 via SpCas9/sgRNA ribonucleoprotein complexes

Gene editing has been revolutionized by CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas technology in a variety of organisms. In bacteria, however, CRISPR-Cas still holds many caveats such as high toxicity of Cas9 and off-target editing effects. In this work we develop a system for the incorporation of Cas9/single guide RNA ribonucleoprotein complexes in bacteria and their successful application for gene editing via homologous recombination. Targeting of a green fluorescent protein (GFP) reporter allows for easy verification of gene-edition via conversion to blue-fluorescent protein (BFP), mediated by the well characterized 196T > C (Tyr66His) mutation.

Gene editing in bacteria via SpCas9/sgRNA ribonucleoprotein complexes

Gene editing has been revolutionized by CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas technology in a variety of organisms. In bacteria, however, CRISPR-Cas still holds many caveats such as high toxicity of Cas9 and off-target editing effects. In this work we develop a system for the incorporation of Cas9/single guide RNA ribonucleoprotein complexes in bacteria and their successful application for gene editing via homologous recombination. Targeting of a green fluorescent protein (GFP) reporter allows for easy verification of gene-edition via conversion to blue-fluorescent protein (BFP), mediated by the well characterized 196T > C (Tyr66His) mutation.