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Subject: NIH STUDY UNCOVERS DETAILS OF EARLY STAGES IN MUSCLE FORMATION AND
REGENERATION
U.S. Department of Health and Human Services NATIONAL INSTITUTES OF HEALTH
NIH News Eunice Kennedy Shriver National Institute of Child Health and Human
Development (NICHD) <http://www.nichd.nih.gov/> For Immediate Release:
Tuesday, January 8, 2013
CONTACT: Robert Bock, 301-496-5133, <e-mail:[log in to unmask]>
NIH STUDY UNCOVERS DETAILS OF EARLY STAGES IN MUSCLE FORMATION AND
REGENERATION Mouse study findings may offer clues for understanding cell
fusion
Researchers at the National Institutes of Health have identified proteins
that allow muscle cells in mice to form from the fusion of the early stage
cells that give rise to the muscle cells.
The findings have implications for understanding how to repair and
rehabilitate muscle tissue and to understanding other processes involving
cell fusion, such as when a sperm fertilizes an egg, when viruses infect
cells, or when specialized cells called osteoclasts dissolve and assimilate
bone tissue in order to repair and maintain bones.
Their findings were published online in the Journal of Cell Biology.
"Through a process that starts with these progenitor cells, the body forms
tissue that accounts for about one-third of its total weight," said the
study's senior author, Leonid V. Chernomordik, Ph.D., of the Section on
Membrane Biology at the Eunice Kennedy Shriver National Institute of Child
Health and Human Development (NICHD), the NIH institute where the research
was conducted. "Our study provides the first look at the very early stages
of this fusion process."
Dr. Chernomordik conducted the study along with researchers at NICHD
(Evgenia. Leikina, D.V.M.,; Kamram. Melikov, Ph.D.; Samristha Sanyal,
Ph.D.; Santosh Verma, Bokke Eun, Ph.D.; Claudia Gebert, D.V.M., Ph.D.; Karl
Pfeifer, Ph.D., and Vladimir.A. Lizunov, Ph.D.) and at Tel Aviv University,
in Israel (Michael M. Kozlov, Ph.D.).
Muscle cells originate from precursor cells known as myoblasts. Myoblasts
fuse to form a single long tubular cell called a myocyte (a muscle fiber).
Muscle tissue is composed of large collections of these fibers. The fusion
of myoblasts into muscle fibers takes place early in fetal development.
With exercise and throughout a person's life, the process is repeated to
form new muscle mass and repair old or damaged muscle.
It takes many hours for cells to prepare for fusion, but the fusion process
itself is very rapid. To study myoblast fusion, the researchers first
blocked the start of the fusion process with a chemical. Ordinarily, the
mouse myoblasts the researchers worked with fuse at varied intervals. By
blocking fusion, and then lifting the block, the researchers were able to
synchronize fusion in a large number of cells, making the process easier to
study.
The researchers identified the two distinct stages of cell fusion and the
essential proteins that facilitate these stages.
In the first stage, two myoblasts meet, and proteins on cell surface
membranes cause the membranes to meld. In the second stage, a pore opens
between the cells and their contents merge. This second step is guided by
proteins inside the cells.
The work identifies two cell surface proteins that act at the start of
myoblast fusion. These proteins belong to a large family of proteins called
annexins. Annexins are also known to play a role in membrane repair and in
inflammation.
The researchers identified the protein dynamin, found inside the cell, as
essential to the second stage of the cell fusion process.
"Dynamin also has an unexplained link to certain rare and poorly understood
myopathies -- disorders characterized by underdeveloped muscles," said Dr.
Chernomordik. "We hope that further examination of the role of dynamin in
cell fusion will lead to a greater understanding of these conditions."
A graphic accompanying this release is available at
<http://www.nichd.nih.gov/news/releases/Pages/010713-cell-fusion-image1.aspx
>. The research article upon which the release is based can be downloaded
free of charge at <http://jcb.rupress.org/content/200/1/3.full>.
About the Eunice Kennedy Shriver National Institute of Child Health and
Human Development (NICHD): The NICHD sponsors research on development,
before and after birth; maternal, child, and family health; reproductive
biology and population issues; and medical rehabilitation. For more
information, visit the Institute's website at <http://www.nichd.nih.gov/>.
About the National Institutes of Health (NIH): NIH, the nation's medical
research agency, includes 27 Institutes and Centers and is a component of
the U.S. Department of Health and Human Services. NIH is the primary federal
agency conducting and supporting basic, clinical, and translational medical
research, and is investigating the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and its programs,
visit <www.nih.gov>.
NIH...Turning Discovery into Health -- Registered, U.S. Patent and Trademark
Office
-------------------
The HTML version of this release contains an Illustration showing how muscle
fibers form at:
<http://www.nichd.nih.gov/news/releases/PublishingImages/cell_fusion.jpg>
###
This NIH News Release is available online at:
<http://www.nih.gov/news/health/jan2013/nichd-08.htm>.
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