Mitosis is a fundamental aspect of cell biology, learned by middle school students the world over. But there are still molecular secrets embedded in the ubiquitous biological process. Researchers from MIT recently learned that daughter cells are given a fresh start by the mother cell which ejects waste products from the cell, in a process called exocytosis, before cleavage. The findings, published this week in eLife, build upon the team’s 2019 paper about the biomass dynamics involved in cell division.
Rather than measure cells using mass spectrometry, which requires lysing cells, the researchers were able to use quantitative phase microscopy and other techniques to image single living cells and determine their dry mass. Cells generally increase in mass as they prepare to split and molecules are constantly entering and exiting through the cell membrane. But the researchers were able to detect a noticeable dip in dry mass between metaphase and anaphase in actively dividing cells. Using fluorescent markers on such cells’ lysosomes, the authors of the paper were able to plainly see when waste was being flushed out early in mitosis.