On August 15th, the international academic journal Development online published the scientific research results of the Zhou Bin Research Group of the Institute of Biochemistry and Cell Biology of the Chinese Academy of Sciences, "The research results of the research group "The sauedd s a d'oedd and the origin dynamics of the cardiac valve mesenchyme".
the first time that the study was based on Nigri-nox homologous recombination, and used Nigri-nox and Cre-loxP systems to build a more precise dual homologous recombination system with the ability to simultaneously mark and trace two separate groups of stem cell groups in the body, using this new system to reveal the origin and dynamics of the cell-filling cells between the heart valves.
the successful use of the Nigri-nox system in the body with the traditional Cre-loxP system offers more technical options for development, disease and regeneration research.
genetic genealogy tracing techniques based on site-specific homologous recombination (SSR) systems are widely used in organ development, disease and tissue regeneration studies.
currently, a variety of SSR systems are commonly used, such as Cre-loxP, Flpe-frt and Dre-rox, the most common use is the Cre-loxP system, when Cre is driven by the promoter of tissue-specific genes, Cre expresses and identifies two loxP sites in the same way, will Transcription between two loxP sites terminates the sequence removal, thus allowing the normal expression of the reported gene after the transcription termination sequence, and since the excision is on the genome, it is permanent and irreversible, so that all cell populations that have expressed Cre and their sub-cells (whether or not Cre is still expressed) are permanently labeled by the reported gene protein.
based on this characteristic, SSR system is widely used in cell origin and destiny research, and the development of a new SSR system will greatly broaden the selection of genealogical tracing technology.
but the development process of life is extremely complex, the cell origin and destiny of different tissues are multi-directional and cross-cutting.
Although The Cre-loxP system has been widely used, Cre is often used in combination with traditional single-report ingress (e.g. Rosa26-LacZ, Rosa26-tdTomato, Rosa26-GFP), cre is driven by a promoter to express a corresponding reporting gene in cre cells, i.e., only one cell type can be labeled and traced, which is not enough for complex developmental disease, regeneration research in the body.
Although previous generations have developed a variety of dual systems (or multi-systems) based on different SSR systems, they have developed a variety of invivage-based research (e.g., R26:FLAP, RC:Fela, R26NZG, RC:FrePe, RC:RLTG), these systems can be classified as the same type, i.e. suitable for marking tracing a certain group of stem cells and their subgroups, and do not have the ability to mark two independent stem cells.
developade a new genealogical tracer technique that can simultaneously label two groups of independent cells is extremely important for development and regenerative medicine.
to fill this technology gap and develop a new SSR system that can be used for gene editing in the body. Based on the Nigri-nox homologous recombination system, researchers at the
Zhoubin research team constructed the world's first inviviable genetically modified tool mouse, Cdh5-Nigri mice, which was regulated by the Nigri-nox system, and combined the Nigri-nox system with the traditional Cre-loxP system to develop a new lineage tracing system that can be used to label two groups of independent cells in the body simultaneously, called R26-Nlr."
R26-NLR reported that the gene mice contained two nox sites and two loxP sites in a staggered form (nox-loxP-Stop-nox-ZsGreen-polyA-loxP-tdToamto), Cre homologous recombinant enzyme mediated The recombination of the reported gene tdTomato, the Nox recombination mediated by Nigri homologous recombinant enzymes, enables the expression of the reporting gene ZsGreen, and when Cre and Nigri are driven by two independent cell-specific promoters at the same time, it is possible to simultaneously label and trace the two separate stem cell groups in the body. Which cell group is marked
depends entirely on the initiator before the Cre and Nigri sequences, out of the limits of the dual-system technology developed by the previous ones.
: The new genealogy tracer technique R26-NLR is compared with the traditional genealogy tracing strategy.
A: Traditional genealogy tracers usually use only a single homologous recombination system (e.g. Cre-loxP, Flpe-frt, Dre-rox, etc.) in which only one cell type can be marked and traced in the same individual.
B: R26-NLR is based on two homologous recombinant systems (Nigri-nox and Cre-loxP) that allow simultaneous marking and tracing of two cell groups in the body.
to further demonstrate the benefits of the new R26-NLR system, the researchers used the system to explore the origin and dynamics of valve-to-valve filling cells during heart development in mice.
mammalian heart consists of four groups of valves, including two groups of chamber valves (two-tip and three-tip valves), and two groups of half-moon valves (aortic valves and pulmonary valves).
previous studies have shown that room valve-to-chamber hyperplial cells are mainly derived from the heart endometry and the heart ventricle, while the half-moon valve-filled cells are mainly derived from the heart endocardial membrane and nerve crucible cells.
to more easily observe the dynamic changes in the contribution of the two groups of stem cells to valve development in the same individual, the researchers mated the R26-NLR system with the Tbx18-Cre mice (labeling the heart ventricle) and the Cdh5-Nigri mice (labeled the heart endosine) to obtain Tbx18-Cre that can mark both the heart and heart endometarium; Cdh5-Nigri; R26-NLR trigene mice, through the mouse development of various points in time sampling analysis, found that the contribution of these two groups of stem cells to the chamber valve is dynamic change, Before E14.5, the cavity wall side valve (in contact with the ventricle wall) of the filling cells mainly from the endocardial membrane, E14.5 days later, with the valve valve development From the near end of the valve to the far end, it is gradually replaced by the interstitial cells of the source of the exome membrane differentiation (EPDCs), which can continue until about P7 days after birth, while the chamber spacer valves of the two-tip and three-tip valves (in contact with chamber spacing) are formed from the valve to the heart endomelis.
, the researchers also obtained Wnt1-Cre; Cdh5-Nigri; R26-NLR trigene mice, in the body at the same time label tracer nerve cell (Wnt1-Cre) and endocardial cells, through the mouse development of various point-in-time sampling analysis, found that the half-moon valve development of intermediate charge cell source is different from room valve, in early development (e13.5 or so), Inter-asthele valve hyperficion mainly originates from nerve cell, with valve development until the mouse is born, the proportion of the source of the nerve crucible cell decreased, the proportion of the endocosis source increased, but will not be replaced, and ultimately maintain a ratio of 3:2 or so, and the pulmonary valve development did not observe similar dynamic changes, basically maintained a ratio of 3:1. The successful application of the R26-NLR system in the
in vivo research shows its application prospect in solving the scientific problem of multicellular origin, and also provides a reliable technical idea for more accurate genealogy tracing technology.
under the guidance of researcher Zhou Bin, the research work was completed by graduate student Liu Yu, and received strong support from Professor Lu Ailan, Professor of the Chinese University of Hong Kong, And Sylvia Evans, Professor of the University of California, and received financial support from the Chinese Academy of Sciences, the State Fund Committee, the State Ministry of Science and Technology, and the Shanghai Science and Technology Commission.