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Gene expression in regenerating sea stars
Sarah E. DeWeerdt

Starfish are famous for their powers of regeneration. They can re-grow lost limbs, and a new animal can even grow from one arm and a fragment of the body. More properly known as sea stars, starfish may be useful models for studying wound healing and regeneration in humans, and scientists are analyzing gene expression in the gray sand star, Luidia foliolata, to identify genes involved in regeneration.

When the tiny, transparent larvae of L. foliolata are cut in half, each half regenerates to become a whole larva. Michael C. L. Vickery, of the University of Alabama at Birmingham, and colleagues compared gene expression in healthy larvae to that of regenerating larvae 6 hours after cutting. Using a method called suppression PCR-enhanced subtractive hybridization, the team screened dozens of genes. They found nine cDNAs, representing expressed genes or pieces of genes, that were present in regenerating larvae but not intact larvae.

One of these genes, which the researchers named sea star regeneration-associated protease (srap), has a DNA sequence similar to the gene for plasmin, a protein found in humans and many other vertebrates. Plasmin plays a role in sculpting the shape of the body during embryonic development and also contributes to wound repair. The researchers speculate that srap may play similar roles in L. foliolata. To understand how the process of regeneration unfolds, the team plans future experiments to study gene expression in regenerating sea star larvae at various times after cutting.

Vickery believes that L. foliolata, which burrows in the sand off the Pacific Coast of the U.S., will be a useful model for understanding regeneration in humans, because similarities in the very early stages of embryonic development suggest that sea stars and vertebrates are quite closely related. Many of the genes involved in development are also thought to be involved in wound healing and regeneration.

Compared to sea stars, humans have quite limited powers of regeneration, consisting mainly of wound repair and re-growth of a few tissues, such as the liver. Not only can the body not re-grow lost limbs, but some types of cells, such as heart muscle cells and nerve cells, are frustratingly incapable of growing back after damage. Nevertheless, "many studies have demonstrated or suggested a latent regenerative capacity in vertebrates, including humans," the researchers write in a recent issue of Gene.

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Vickery, M.C.L. et al. Utilization of a novel deuterostome model for the study of regeneration genetics: molecular cloning of genes that are differentially expressed during early stages of larval sea star regeneration. Gene 262, 73-80 (January 10, 2001).

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