A research team led by Jing Naihe, a researcher with the Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences (CAS), has established a molecular map for genes in mouse embryos with several scientists.

Their discoveries, which were published on the website of the UK-based journal Nature on Aug 8, enabled the tracking of cell "ancestors" in different locations and paved the way for more efficient methods of obtaining stem cells for certain human organs.

This may in turn promote the development of stem cell-related regenerative medicine.

A living individual develops from the embryo emerging from a fertilized egg. The cells in the embryo multiply from generation to generation, and ultimately produce a complete individual.

It is essential to understand the origin of life and trace the causes of diseases by exploring the "genealogy" of cell families, tracing their "ancestors" at an early stage of embryonic development and analyzing their "lineages".

In the early stage of embryonic development, the fertilized eggs first develop into blastocysts, and then form three embryonic layers: outer, middle and inner.

The ectoderm eventually develops into nerve, skin and other tissues, the mesoderm develops into heart, blood, muscle and bone, and the endoderm develops into lung, liver, pancreas and intestines.

The formation of the three embryonic layers directly affects whether the fetus can be born smoothly from the mother. However, it is not clear how cells multiply, differentiate, and determine their destiny. The development of each cell from the embryonic stage remains to be revealed.

Jing’s team developed a new technique to analyze the transcription histology of cells in different spatial locations and developmental times of early mouse embryos, and successfully mapped a three-dimensional stereogram of cell growth trajectory with both temporal and spatial information.

"Scientists can trace the ancestors of different embryonic cells through this encyclopedic growth trajectory," Jing said, adding that after tracing the origin, the team found that some of the endodermal cells originally thought to have developed entirely from the epiderm were likely to have "crossed" the epiderm directly from the primitive endoderm, while some specific cells were thought to have followed other differentiated paths.

Mesoembryonic and ectodermal cells may have common "precursor" cells, he said, adding that these discoveries have overturned people's understanding of traditional cell genealogy.

In recent years scientists have mostly followed the "growth" path of cells, and differentiated the "precursor" cells from pluripotent stem cells for regenerative medicine and disease-related research into stem cells.

The findings will help to improve the differentiation system of cells in liver, pancreas, spinal cord and other organs, and provide a new possible way to obtain the stem cells of organs through differentiation, which may be more efficient and faster than the path based on "traditional cell genealogy", said Peng Guangdun, co-author of the paper and a researcher with the CAS Guangzhou Institute of Biomedicine and Health.

Jing said that the findings are a major revision and supplement to the classical hierarchical pedigree theory of developmental biology, and will greatly promote the development of early embryonic development and stem cell regeneration medicine.

Spatial expression domains of embryonic spatial transcriptome during early embryonic development and their similarities. [Image: CAS]

ture A presents the spatial expression domains of mice from early implantation (E5.5) to late gastrointestinal motility (E7.5); Picture B shows the similarity of spatial expression domains of early embryos. The color strips at different stages represent gene expression domains: MOR-morula, ICM-endoderm, Epi-epiderm, PrE-primitive endoderm, En-endoderm, E1-endoderm gene expression domains 1, Ect-ectoderm, PS-protoderm, M-mesoderm, MA-front mesoderm, and MP-back mesoderm. The correlation between structural domains is calculated, and the thickness of the connection line represents the relative correlation.

Source: China Science Daily

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