Eukaryotic cells — the cells that make up most of life as we know it, including all animals, plants and fungi — are highly structured objects.
These cells assemble and maintain their own smaller interiors: membrane-bound organelles such as the nucleus, which stores genetic information, or mitochondria, which produce chemical energy. But much remains to be learned about how they organize themselves into these spatial compartments.
Physicists at Washington University in St. Louis have performed new experiments showing that eukaryotic cells can powerfully control average fluctuations in organelle size. By demonstrating that organelle size obeys the universal scaling relationship the scientists predicted theoretically, their new framework shows that organelles grow in random bursts from a finite pool of building blocks.
The study was published on January 6 in Physical Review Letters.
“In our work, we consider organelle growth steps — far from ordered ‘brick-by-brick’ assembly — to burst randomly,” said Shankar Mukherji, assistant professor of physics in the College of Arts and Sciences. .
“This bursting fundamentally limits the precision of organelle size control, but also keeps the noise of organelle size within a narrow window,” Mukherji said. “Burst growth provides a general biophysical mechanism by which cells maintain, on average, a reliable but plastic organelle size.”
Organelles must be flexible enough to allow cells to grow or shrink as their environment demands. Nevertheless, the size of the organelles must still be kept within a certain range. Biologists have previously identified certain molecular factors that regulate organelle size, but this study provides new insights into the quantitative principles of organelle size control.
Although this study used budding yeast as a model organism, the team is excited to explore how these assembly mechanisms can be exploited in different species and cell types. Mukherji said their plan to study these robust patterns could teach us how to harness organelle assembly for bioengineering applications and how to spot defects in organelle biogenesis in disease settings.
“Patterns of organelle size robustness are shared between budding yeast and human iPS cells,” Mukherji said. “The underlying molecular mechanisms that generate these bursts have not been fully elucidated and are likely organelle-specific and potentially species-specific.”
Funding: This research was supported by the National Institutes of Health (NIH R35GM142704).
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Material Provided by the Washington University in St. Louis. Originally written by Talia Ogliore. NOTE: Content may be edited for style and length.