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Proteins guide early heart development.

Proteins guide early heart development

During the first few months of development, a human embryo's single-chambered heart must somehow transform itself into the four-chambered heart that, if all goes well, will serve as a powerful pump throughout life. If embryonic heart development goes awry, a life-threatening defect -- such as a hole in the heart -- can result.

In a quest that may someday lead to treatments for infants with heart defects, scientists are homing in on a set of proteins that may guide this in utero development.

The embryo's single-cavity heart contains a layer of jelly-like material sandwiched between an outer layer of muscle tissue and an inner tissue layer known as the endocardium. Between the fourth and eighth weeks of gestation, certain cells lining the endocardium, called endothelial cells, break away and migrate through the cardiac jelly, eventually forming tissue pads that divide the heart into four chambers.

But what triggers the cellular journey? Roger R. Markwald, a biologist at the Medical College of Wisconsin in Milwaukee, and his colleagues suggested in 1989 that so-called adherons -- packets of proteins carrying a glue-like substance -- adhere to embryonic endothelial cells and somehow cause them to begin their migration. The team reported experiments demonstrating that chick-embryo endothelial cells placed atop a gel layer in a petri dish broke away from their neighbors and started to travel into the gel when exposed to adherons isolated from the cardiac jelly of embryonic chick hearts.

The researchers have now begun to characterize the mysterious adherons. Their unpublished results suggest that cardiac adherons contain at least five key proteins, Markwald told SCIENCE NEWS. The team now hopes to identify each of these proteins and find out how they guide the crucial transformation to a four-chamber heart. Ultimately, says Markwald, such knowledge might enable researchers to develop drugs that spur self-repair in a newborn's defective heart.
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Author:Fackelmann, Kathy A.
Publication:Science News
Date:Jan 26, 1991
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