Macho Muscle Cells Force Their Way To Fusion

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Macho Muscle Cells Force Their Way To Fusion

http://www.medicalnewstoday.com/articles/216457.php

In fact, according to new research from s Hopkins, the fusion of muscle

cells is a power struggle that involves a smaller mobile antagonist that points

at, pokes and finally pushes into its larger, stationary partner using a newly

identified finger-like projection.

In a report published Nov. 29 in the Journal of Cell Biology, the researchers

described experiments using fruit fly embryos to identify an invasive projection

propelled by the rapid elongation of actin filaments as the main player in the

cellular power struggle.

" We found that two muscle cells don't simply open up their membranes and

symmetrically fuse together, " says H. Chen, Ph.D., an assistant

professor in the department of molecular biology and genetics, s Hopkins

University School of Medicine. " Muscle cell fusion is actually an invasive

battle. "

Before the new study, it was assumed that actin-enriched blobs sit atop the

membranes of muscle cells preparing to fuse, equally dispersed. But by observing

the accumulation of these blobs by genetics means, the team concluded that the

actin structure is produced in only one of the two muscle cell types the

aggressive fusion-competent myoblast and not in the stationary founder cell.

Further analyses of the images, made with an electron microscope, showed the

myoblast is extending multiple finger-like protrusions toward founder cells and

ultimately forcing fusion with the founder cell by forming an open pore.

" Where we once saw only blobs of actin, now we could clearly see finger-like

protrusions emanating from one cell into another, " Chen says. " That really

helped us make the connection between this structure and invasive podosomes. "

The new work shows what is believed to be the first time that an invasive

podosome-like structure has been found in developing tissue of any kind, Chen

says, noting that although podosomes were discovered several decades ago in

studies of cells growing in dishes, they have not been seen in a developing

animal or implicated as a mechanism in cell fusion.

" It may be that this new understanding of muscle cell fusion will apply

generally to other cells that fuse, " Chen says, " such as egg and sperm, for

instance, as well as bone resorption cells and cells that are vital for immune

responses. "

Muscle fusion is an integral part of muscle regeneration in genetic and acquired

muscle diseases, and an accurate understanding of this basic cellular event

could have important clinical applications in people with muscular dystrophy and

other degenerative disorders, according to Chen.

The research was supported by the National Institutes of Health and the American

Heart Association.

In addition to Chen, authors on the paper are L. Sens,

Shiliang Zhang, Peng Jin, Rui Duan, Fengbao Luo and Parachini, all of

s Hopkins; and Guofeng Zhang of the National Institute of Biomedical Imaging

and Bioengineering.

Source: s Hopkins Medicine