'eLife' Egg cells have a backup plan

In order to reproduce successfully, egg cells must divide perfectly

In a new study, Northwestern University researchers have discovered a previously unknown mechanism in C.

Sadie Wignall of Northwestern University, who led the study, said: "Before our work, certain proteins were thought to be necessary for cell division

The research was published today (March 29) in the journal eLife

Wignall is an associate professor of molecular biological sciences in Northwestern's Weinberg College of Arts and Sciences

When the egg is fertilized with the sperm, the resulting embryo begins to divide rapidly and eventually develops into a healthy organism

While other cells in the body divide perfectly 99% of the time, egg cells are prone to inexplicably go wrong

To understand why egg cells are more prone to errors, Wignall studied a football-shaped structure called the spindle, which organizes genetic material before egg cells divide

"The spindle is like a machine," Wignall said

The spindle consists of long rope-like structures called microtubules

"Motorins bind to and move along microtubules, just as humans walk on their legs," Wignall said

Before Wignall's new study, researchers thought that two motor proteins (dynein and kinesin 12) were primarily responsible for this task

"When we removed these proteins, the entire spindle exploded," Wignall said

In the absence of dynein and kinesin 12, another dynein, called kinesin 5, comes out of hiding to perform its backup tasks
.
Ultimately, this previously unknown mechanism restores the spindle structure, allowing the chromosomes to be pulled apart
.

While the study was done in C.
elegans, which is often used as a model for reproduction, Wignall believes a similar mechanism may exist in humans
.
But because so few human eggs are donated to scientific research, researchers are exploring questions and figuring out details by studying biological models before examining humans
.

"All the components in our study are also present in human eggs," Wignall said
.
"Spindles seem to form in the same way in humans, and even look exactly the same
.
It would be very interesting if humans also had this backup mechanism
.
"

Multiple motors cooperate to establish and maintain acentrosomal spindle bipolarity in C.
elegans oocyte meiosis