The unique mechanism of the genetic state of the egg is revealed

bing team at the Institute of Biophysics of the Chinese Academy of Sciences in The United States discovered Stella, the first safeguard factor for the normal establishment of methylation levels of DNA in the egg cell genome. The paper was published recently in Nature.
only a limited number of eggs in the lifetime of female mammals. The level of DNA methylation of the egg is very low, only about half the level of DNA methylation of sperm and most end-differentiated somogene cells. However, it is not clear how this unique state of DNA methylation of the egg is formed, what factors are regulated, and what is biologically significant.
researchers have sifted through the cDNA library of mouse egg cells to identify a new type of DNA methylation regulatory gene, Stella. This time, the researchers explored Stella's role in ovarian cell maturation and found that Stella prevented UHRF1 from accumulating in the ovarian nucleus through an active nuclear transport process. Stella knocked out abnormal UHRF1 intranucleotic accumulation, excessive DNA methylation, and doubled the level of methylation of the mature egg genome to a level similar to that of sperm DNA methylation. The study found the first regulatory factor to protect the unique methylation state of the egg.
addition, the study found that the abnormally high methylation caused by Stella's absence occurred mainly in the silent genomic region, seriously affecting the quality of mature eggs and the activation of the maternal genome of the second-cell stage embryo after fertilization. Therefore, the methylation spectrum unique to the maternal genome is very important for development, and reveals the biological significance of the unique genome low methylation state of the egg.
study found that abnormal methylation in Stella's missing egg cells was catalyticized by DNMT1. The findings rewrite the textbook classification of DNA methylase. What's more, it provides clues to functional interpretation of the high expression of DNMT1 in a variety of cell types in the body that have withdrawn from the cell cycle, such as ovaries and neurons, and has important implications for the significance of DNA methylation responsible for DNMT in the aging process. (Source: China Science Journal)