The protein Mnd2 inhibits premature separation of chromosomes during the formation of gametes. The now published discovery of this regulatory function may help to understand the origin of some common congenital chromosome defects. The project of a team of the University of Vienna funded by the Austrian Science Fund (FWF) contributes to the Campus Vienna Biocenter maintaining a top-level position in the field of cell division research.
During the division of somatic cells (mitosis) newly duplicated chromosomes (sister chromatids) separate and segregate to opposite daughter cells. The cell division, which leads to the formation of gametes (egg and sperm cells), serves a different purpose. In this cell division called meiosis, the two complete sets of chromosomes (maternal and paternal ones) in each body cell are reduced to a single one.
Prof. Franz Klein and his colleague, Ph.D. student Alexandra Penkner from the Department of Chromosome Biology of the Max Perutz Laboratories at the Campus Vienna Biocenter, have now published results on an important regulation of this process in the journal CELL. These findings show that the premature segregation of sister chromatids with lethal consequences are inhibited by a protein named Mnd2.
The research carried out on the model organism Saccharomyces cerevisiae (yeast) is explained by Prof. Klein, "Until they are separated, the sister chromatids are linked by a protein ring called cohesin. This linkage ensures their correct segregation to the daughter cells later on. We have now discovered an important role of the protein Mnd2 in stabilising this arrangement up to the right moment in the cell division."
The command for opening the cohesin rings, which initiates the division, comes via the anaphase promoting complex (APC/C). Klein explains, "While we worked on Mnd2, colleagues in the USA and Germany isolated Mnd2 as one of 13 subunits of the APC/C. However, the important role of Mnd2 was not revealed. Because only during meiosis, when the gametes are created, does it become essential."