Release date: 2017-05-10
On May 2, the Journal of Cell Biology published a research paper entitled "Retinal Adult Stem Cell Embryonic Origin Double Potential Cells" by the Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. He Jie Research Group, Center for Excellence in Brain Science and Intelligent Technology, completed. The study used rainbow fish cloning analysis to reveal the precise localization of retinal stem cells in the ciliary margin of the retina at the single-cell level. At the same time, a class of resting cells that have not been reported yet are found in the marginal zone. In addition, this study used in situ cell lineage to elucidate the precise cell lineage of embryonic development of retinal stem cells, revealing that retinal stem cells originate from a group of bipotent cells in the epithelial cells of the optic vesicle. This work has discovered the cell lineage basis of retinal stem cell development, and provides an important experimental basis for further revealing the molecular mechanism of retinal stem cell development and finally realizing the in vitro reconstruction of retinal stem cell microenvironment.
In lower vertebrates, retinal stem cells are located in the ciliary marginal zone of the retina. In the life of a lower vertebrates, such as zebrafish, the retina can grow. Whole life-long retinal growth is achieved through the proliferation and differentiation of retinal stem cells. In the process of evolution, higher vertebrates, the retinal ciliary marginal zone cells, have a weaker ability to produce various retinal neurons. But there is growing evidence that in mammals, cells in the ciliary marginal zone of the retina still have the potential to produce new neurons, but in the in vivo environment these potentials are silenced. The reason is still unclear, which is also a major proposition in the field of neurodevelopment and regeneration. Therefore, a better understanding of the microenvironment of lower animal retinal stem cells and their embryonic origin will be more helpful in understanding the causes of silencing of higher vertebrates, such as mammalian retinal stem cells, and provide an important experimental basis for finding ways to activate these stem cells.
In the past, zebrafish was used as a model animal to study the development of retina. It was found that the eye stalk developed into a visual vesicle structure with intermediate epithelial cells and lateral epithelial cells through valgus, and the epithelial cells in the optic vesicle migrated into the lateral epithelial cells. It gradually develops into a cup structure, and the stem cells of the retina are derived from the epithelial cells of the group. However, the precise localization of retinal stem cells in the retina and the precise cell lineage pattern of embryonic retinal progenitor cells developing into retinal stem cells are unclear.
The research team used zebrafish as a model animal and used rainbow fish-based clonal analysis to accurately locate retinal stem cells in the outermost layer of the second or third layer of the retinal ciliary marginal zone. Retinal stem cells have a longer cell cycle than other retinal precursor cells in the ciliary margin of the retina. In addition, the team also found that the outermost layer of cells in the ciliary marginal zone of the retina is a new type of cell that is completely at rest. RNA in situ hybridization experiments showed that they neither expressed molecular markers of retinal stem cells nor expressed or weakly expressed molecular markers associated with retinal pigment cells. Further research is needed on the maintenance of retinal stem cells by such new cells.
Based on the accurate localization of retinal stem cells, the researchers further sought the embryonic origin of retinal stem cells. Kaede is a photoconverting protein that changes from green to red under 405 nm laser irradiation. The mRNA of the nuclear localization phototransformer nls-kaede was injected into the embryo of wild-type zebrafish. In the optic vesicle stage of retinal development, single-cell phototransformation of the optic vesicle epithelial cells expressing the Kaede protein, by analyzing clones derived from a single epithelial cell, the researchers found that: retinal stem cells can only be a group of epithelial cells in the optic vesicle Double-potential cells are produced; this group of bipotent cells produce retinal stem cells while producing retinal pigment cells, which are a group of cells with relatively short cell cycles. RNA in situ hybridization experiments showed that these double-potential cells expressed both the molecular markers of retinal stem cells and the markers of retinal pigment cells. Other cells in the epithelial cells of the retinal optic vesicle can only produce retinal pigment cells or retinal precursor cells.
This work reveals the cell type composition and characteristics of the microenvironment of the retinal ciliary marginal region at the single cell level, providing an experimental basis for further exploration of the steady state maintenance of the retinal stem cell microenvironment. In addition, the discovery of dual-potential cells provides a cell lineage basis for further study of the molecular mechanisms of retinal stem cell embryo development, providing the possibility to ultimately understand the mechanisms of retinal stem cell production and maintenance.
The work was completed by assistant researcher Tang Xia and intern Gao Jianan under the guidance of researcher He Jie; Jia Xinling of the research group assisted in the completion of important RNA in situ hybridization experiments; during the study, the project also received health science research from Shanghai Academy of Health Sciences. The assistance of Pan Yujun's research team. The work was funded by the National Natural Science Foundation of China (31471042) and the Youth Thousand Talents Program.
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Figure: During the period from 18 hours to 26 hours after zebrafish birth, rapidly dividing bipotential cells (BP, blue) in the middle epithelial cell layer of the optic vesicle migrate into the outer epithelial cell layer, during which the bipotential cells proliferate. Produce a precursor cell of retinal pigment epithelial cells (PP, black) and a precursor cell of retinal stem cells (SP, red). Subsequent precursor cells of the retinal stem cells (SP, red) exhibit a longer cell cycle and produce three types of cell lineage patterns through cell division: a non-nickname split produces a retinal stem cell (S, red) and a CMZ Tip resting cells (D; black/red; accounting for 60% of the cell lineage produced by RSC); the second is asymmetric division to produce a retinal stem cell RSC (S, red) and a retinal precursor cell (RP, red ; accounted for 38% of the cell lineage produced by RSC; the third is symmetric division to produce two retinal stem cells (S, red; 2% of the cell lineage produced by RSC). At the same time, retinal pigment epithelial precursor cells (PP, black) produce two types of cell lineages through proliferation and division: one cell lineage includes two retinal pigment cells (P; black, 64%); The lineage included a retinal pigment cell (P, black) and a CMZ tip resting cell (D, black/red; 36%). CMZ tip resting cells (D, black/red) can be produced either by retinal pigment epithelial precursor cells (PP, black) or by retinal stem cell precursor cells (SP, red).
Source: Chinese Academy of Sciences website
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