How do our limbs develop from a fertilized egg to a complete human body? Scientists have found some clues using single-cell technology. On January 7th, the reporter learned from Sun Yat sen University that Professor Zhang Hongbo's research group at the Zhongshan Medical College of the university has released the first single cell spatiotemporal map of human limb development, which analyzes the cellular evolution path and spatial position determination process of fetal limbs. The related research papers were published in Nature. The spatiotemporal regulatory mechanism of limb construction is a classic developmental biology challenge. Zhang Hongbo gave an example, saying, "Cutting off the cell clusters that formed forelimbs in chicken embryos and transplanting them to the back, one can actually grow complete wings. Removing the legs of adult salamanders, they can quickly regenerate, even after 8 to 10 cuts, they can still grow new legs with almost no visible scars. However, most mammals, including humans, have lost this ability to regenerate in adulthood during evolution." In the past, scientists often could only track the developmental pathways of a certain type of cell, and could only track the developmental pathways of two to three types of cells simultaneously, without being able to see how the fate of all cells evolved. For determining the spatial position of cells, scientists have limited knowledge of the number of genes obtained by slicing embryos and staining single or few cells. The development of single-cell transcriptome technology and single-cell spatial transcriptome technology has made it possible to explore cellular evolution processes. Zhang Hongbo's research team continuously sampled embryos from the beginning of the fifth week to the ninth week, obtaining over 100000 cells, each containing approximately 2000 genes. Through computational analysis, the team took the lead in constructing a detailed single-cell map of human limb development that includes all cell types. Through the team's independently developed single-cell data analysis tool - DEAPLOG, they are also able to better identify the characteristics of each cell, identify key genes, and anchor these genes to the path of cell evolution. With this information, the team can further verify through experiments which genes contribute to the disproportionation of cell fate. The co first author of the paper and postdoctoral fellow of Zhang Hongbo's team, Zhang Bao, introduced that using this map, it is possible to intuitively track the cell types generated at specific times and regions, identify new cell types, and characterize the key genes activated by different types of cells. "When the expression of these genes does not follow established patterns and plays a key regulatory role, it may lead to special developmental phenotypes, such as short and multi finger developmental abnormalities," said Zhang Bao. (Lixin News Agency) (Reporter Long Yuemei, Correspondent Zhu Jiahao, Li Jianping)