The blueprint of a cell: how cells organize organelle growth
Hyperspectral imaging has provided an insight into how cells organize and prioritize organelle growth.
As cells grow, their organelles also need to grow. But do all the organelles grow at the same rate? Researchers at Washington University in St. Louis (MO, USA) have used rainbow yeast and hyperspectral imaging to gain insights into how organelles grow in eukaryotic cells.
The coordination of organelle growth with overall cell growth has been explored primarily through scaling relationships between organelle sizes and host cell sizes. For example, it’s widely accepted that the volume of the nucleus scales linearly with the size of its host cell, as do the endoplasmic reticulum, vacuoles and mitochondria. However, our knowledge of scaling relationships among organelles is lacking.
To investigate this, the researchers used ‘rainbow yeast’, a strain of Saccharomyces cerevisiae that expresses fluorescent labels for six major organelles: peroxisomes, vacuoles, endoplasmic reticulum, Golgi apparatus, mitochondria and lipid droplets.
They cultured the cells in media containing varying amounts of glucose and used hyperspectral imaging to image the growing rainbow yeast cells. The technique allowed them to visualize how all the organelles changed at the same time.
How it works: the dynamic G protein-coupled receptor
A GPS-like technique has been used to track G protein-coupled receptor movement, revealing how these essential receptors function.
“Using techniques from data science, we could see how the cells patterned themselves in terms of the space for organelles as we changed the conditions they were grown in or as we changed their signaling pathways,” explained corresponding author Shankar Mukherji.
They found that organelles grow in coordinated patterns or ‘modes’ in response to nutrient availability, with some organelles growing faster than others, which allows the cell to meet increased metabolic demands.
They found that the vacuole helps keep the cell growing at a steady rate in a constant environment. “The vacuole seems to be really good at buffering the cell against randomness,” Mukherji commented. “At the same time, if the cell actually needs to change its growth rate – because its environment changes or something – then this is the organelle that seems to respond in the right way.”
Their results also suggest that organelle growth is dictated by cell size and growth rate independently, which could help cells balance these competing demands and explain why eukaryotic cells exhibit a highly diverse spectrum of cell sizes.
Next, the team plans to characterize organelle growth in human cells. “It’s possible that we’ll find that the normal relationship between a cell’s organelle profile, its size and its growth and metabolic properties become abnormal in disorders that feature abnormal metabolism, from cancer to diabetes to immunological diseases,” Mukherji commented. “Whether we can uncover these patterns – and whether they are only diagnostic, prognostic or actually underlie disease – is something we’re excited to get working on!”
