How molecular muscles help cells divide( New Haven Conn. Time-lapse videos a...)

New Haven, Conn. Time-lapse videos and computer simulations provide the first concrete molecular explanation of how a cell flexes tiny muscle-like structures to pinch itself into two daughter cells at the end of each cell division, according to a report in Science Express.

Cell biologists at Yale and physicists at Columbia teamed up to model and then observe the way a cell assembles the contractile ring, the short-lived force-producing structure that physically divides cells and is always located precisely between the two daughter cell nuclei.

This contractile ring is thought to operate like an old-fashioned purse string, said senior author Thomas D. Pollard, Sterling Professor and Chair of the Department of Molecular, Cellular & Developmental Biology at Yale. It constricts the cell membrane into a cleavage furrow that eventually pinches the cell in two.

Living cells divide into two daughter cells to reproduce themselves. In one-celled organisms like yeast, each cell division yields a new creature. In humans and other multicellular species, cell division creates an adult from an embryo. In fully developed adults, it provides necessary replacements for cells that are continuously dying in the course of natural wear and tear.

Scientists have long studied aspects of how cells actually make this division the structure of the cellular machinery, how it assembles and how the machine works. Since the 1970s, it has been known that the contractile ring is made up of muscle-like actin and myosin contractile proteins that are involved a process in some ways similar to the muscle contraction used to move arms or legs. However, there was no plausible mechanism to explain how it worked.

We found that fission yeast cells assemble their contractile ring using a search, capture, pull and release mechanism, said
'/>"/>