Our cells have specialized parts called organelles, and scientists have learned more about one of them, the Golgi apparatus. It is made up of a series of pouches, and because it is responsible for packaging proteins and sending them to their proper location, is a critical center for cellular transport. The new work, by researchers at the University of Alberta, has called current assumptions about its composition into question.
"The Golgi sorts material as it is made and directs it to different locations. It is like a cellular post office. Our research - which goes back in time to examine how cells evolved over billions of years - challenges existing theories around how the cell's Golgi is structured," explained the study leader, Joel Dacks, a U of A cellular biologist and Canada Research Chair in Evolutionary Cell Biology. "This is critical because when this important element of a cell's membrane trafficking system malfunctions in humans, diseases such as Alzheimer's and Parkinson's occur."
The work was performed along with a team of researchers in the Czech Republic and seeks to provide insight into the fundamentals of biology. We gain a better understanding of disease when we know more about the basics. "You can't figure out why your car doesn't run if you don't know how cars work in the first place,” Dacks continued.
Scientists thought that one gene gives the Golgi apparatus its hallmark look - a series of flattened membrane-enclosed disks that are fused together, and known as cisternae, he noted.
First author Lael Barlow, a Ph.D. student, used existing and new genome sequence data and computational analysis to study the evolution and occurrence of genes that are considered to be responsible for Golgi stacking across a wide range of organisms, including amoeba, fish, and humans.
"After testing every gene proposed as responsible, we found that none of them match the predicted pattern of presence and absence across genomes as the gene for stacking of the Golgi," said Barlow.
The authors have now suggested an explanation that has been proposed before; many different kinds of genes acted in complementary and redundant ways. This theory may explain how it arose and should be investigated further.
"The analogy would be that instead of a great song being the result of a single essential solo artist, with backup singers, the song is the result of a choir and many choristers that can compensate for one another," added Dacks.
This work has provided an incredibly detailed picture of Golgi organization in ancient cellular origins. It has revealed that the organelle was more complex than thought. It also shows that the cisternae, or pancake-style organization, was created over one and a half billion years ago.
"It's very exciting, kind of like replacing old grainy aerial photos of a Mayan settlement with much higher-resolution images of the same site, showing that the society was more complex than anticipated at that time point and how it was organized," said Dacks. “This work points to a new path to understanding the organization of a critical part of our cells and brings into the light an even more detailed picture of our deep evolutionary history."