Release date: 2017-07-20
Chinese scientists have recently made major scientific breakthroughs in chromosome 3D structure and reprogramming of chromosome structure during early embryo development. The relevant results were published on the internationally famous journal CELL on July 13, 2017.
If the human DNA is drawn into a straight line, the length is about 2 meters, but the diameter of the general nucleus is only about 5 to 10 microns. Therefore, how to properly fold and store genomic DNA into the nucleus is a very important scientific issue. At the same time, existing studies have shown that the three-dimensional spatial folding of genomic DNA plays a very important role in how the nucleus directs the function of cells.
For most animals, including our humans, life begins with a combination of sperm and egg. However, the nuclear structure of the sperm nuclei and eggs is very different from other somatic cells in our body. The sperm nuclei are very small, only about 1/10 of the common nuclei. The chromosomes are packed in protamine and are in a highly compressed state. The nuclei of mature eggs are in the middle of division, and the chromosomes are in a highly compressed state, with most Cells still have very large differences. Therefore, after fertilization of sperm and eggs, how the chromosomes in the nucleus change and how to become normal cell chromosomes is a scientific problem that has never been understood. At the same time, understanding the changes in the high-level structure of chromosomes during mammalian development helps us understand how humans develop from individuals to fertilized eggs.
Based on this research background, the Liujiang Research Group of the Beijing Institute of Genomics of the Chinese Academy of Sciences and the Huang Xingxu Research Group of the Shanghai University of Science and Technology collaborated to study the above issues. Due to the limited number of mammalian gametes and early embryos, the research team solved the problem of using a small number of cells to establish a 3D chromosome structure map to obtain high-resolution chromosome high-level structural maps of mouse sperm, eggs and early embryos.
Studies have shown that mature eggs have no topological domains (TADs), and ultra-long-range chromosome interactions prevail in sperm. At the same time, it was found that the high-level chromosome structure in the fertilized egg and the 2-cell stage embryo is almost non-existent. As the development progresses, the high-level chromosome structure is gradually established. At the same time, the establishment of high-level chromosome structures does not depend on the activation of the transcription of the fertilized egg genome, but on the replication of the genome. In addition, this study first discovered the association between high-level structure of chromosomes and DNA methylation, and found that early development of DNA demethylation is also associated with higher-level structures of chromosomes.
The results of this study have laid an important foundation for understanding how mammals develop from a fertilized egg into a multifunctional individual, paving the way for researchers to understand the true 3D genomic structure of early embryos, and the early embryonic development of mammalian cells is high. Resolution Chromosome Advanced Structure Atlas data will provide valuable resources for epigenetic and bioinformatics research, helping to reveal the mysteries of embryonic development.
The research was supported by the pilot project of the Chinese Academy of Sciences, the Natural Science Foundation of China, and the National Key Research and Development Project of the Ministry of Science and Technology.
Source: Sina Pharmaceutical News
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