DNA is extremely compressed into chromosomes, which are essential for cell division. During mitosis, chromosomes ensure that the genetic material is distributed equally throughout the daughter cell. Sense that the genetic material is distributed equally throughout the daughter cells. It’s interesting to note that different organisms have different mitotic chromosomal sizes and levels of DNA condensation. It is still unclear how this is controlled or what element controls mitotic chromosomal development and size.
Dr. Yasutaka Kakui of the Waseda Institute for Advanced Study, Frank Uhlmann of the Chromosome Segregation Laboratory at the Francis Crick Institute, and Toru Hirota of the Division of Experimental Pathology at the Cancer Institute of the Japanese Foundation for Cancer Research headed a team of researchers that set out to solve this mystery.
How did it begin? Kakui was inspired to pursue this research by his passion for chromosomes. “How is genome-wide DNA kept in cells?” It’s a long-standing, unanswered question. “We need to comprehend the chemical foundation for chromosomal development in order to increase our understanding of how cells accurately transmit genetic information to succeeding generations.” And that served as the motivation behind this investigation, the results of which were reported in cell reports.
DNA is significantly compressed to produce chromosomes during mitosis. Condensin, a large protein ring complex, is crucial to the compaction process. It compresses DNA by generating loops at specific binding locations. Therefore, condensin is essential for DNA compaction, which is strongly related to chromosomal dimensions, with thicker chromosomes being more compressed, according to scientific research. Additionally, they are aware that each species has a unique pattern of condensin-binding sites. However, it is still unknown how exactly condensin and chromatin interactions affect chromosomal size.
To answer the pertinent concerns, the researchers looked into several aspects of condensin and chromatin interactions. In both budding and fission yeasts, S. cerevisiae and S. pombe, they used Hi-C and super-resolution imaging to examine the relationship between mitotic chromatin interactions and chromosomal arm length. There is unambiguous proof that in both interphase and mitosis, the distance between chromatin interactions is precisely proportional to arm length. As a result, contacts with shorter arms are shorter, and those with longer arms are longer. We discovered that this is species-specific.
Now, larger chromatin loops result from greater distances between chromatin contacts, both of which are signs of wider chromosomal arms. In order to draw the conclusion that longer chromosomal arms were always wider within a species, the scientists studied both budding and fission yeasts. After making a successful finding in yeasts, they expanded their research to include human cells in an effort to discover similar relationships. “Our surprise finding that longer chromosomal arms are usually thicker in eukaryotic species has helped us better understand how mitotic chromosomes develop during cell divisions,” says Kakui. They would be the first to definitively demonstrate that mitotic chromosome width is determined by chromosomal arm length.
The present theories on mitotic chromosome formation have been challenged by the novel insights into mitotic chromosomal structure provided by this work. Kakui sums up: “According to our research, mitotic chromosome shape can be controlled to prevent chromosome miscarriage, which is thought to be a major factor in the development of cancer cells and/or birth abnormalities like Down syndrome.” “This could potentially alter fertility therapies as well as cancer therapy.”
