beta (TGF-_). Researchers are only beginning to unravel how
TGF-_ works.
Receptors for TGF-_ are found on the surface of virtually every cell of
the body. When
TGF-_ binds to these receptors, signals are relayed inside the cell. The
cellular response to TGF-_ depends on the cell type. In some cells, it stimulates
growth, while in others it is actually a growth inhibitor. For example,
TGF-_ stimulates skin cells to divide, making TGF-_ an excellent wound-
healer.
In earlier research, reported in the December 1994 issue of Nature Genetics,
Marchuk identified the first gene linked to HHT. This gene, called ENG,
is located on chromosome 9 and encodes a protein called endoglin, which
also appears to bind TGF-_.
He hypothesizes that both ALK1 and endoglin are TGF-_ receptors specific
to the cells lining the blood vessels. They might only be needed if the
vessel is injured and needs to be repaired.
"This makes sense with what we know about the disease," Marchuk
said. "Children with HHT usually don't show any signs they have the
disease. But as they age, and presumably acquire mechanical damage to tiny
blood vessels that need to be repaired, the disorder shows up."
Marchuk has shown that families whose disease is linked to defects in the
endoglin gene have an increased risk of developing lesions in their lungs
that can lead to serious, secondary neurological problems. About 30 percent
of people with this form of HHT develop these lung problems.
"We are developing a genetic screen that would identify these people
so they can be followed by their doctors more closely for signs of developing
lung problems," Marchuk said.
By contrast, people whose disorder is linked to this second gene, ALK1,
rarely have lung problems. Like endoglin, this gene provides a blueprint
for a protein found almost exclusively in the cells lining blood vessels.
"We realized when we found the first gene that some fam
'"/>Contact: Karyn Hede George
georg016@mc.duke.edu
919-660-1301
Duke University 31-May-1996Page: 1 2 3 Related biology news :1.
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