A Design for Blood

Under the veil of night, a bloodthirsty vampire bat crawls towards it unsuspecting prey and sinks its teeth into its victim. Although the host is unaware of the bat’s presence, its blood flows freely, providing a meal for the small predator.

After biting its prey, the bat secretes enzymes into its saliva that prevent blood from clotting around the wound. According to a recent study from Texas Tech researchers Caleb Phillips and Robert Baker, this unique ability is the result of a genetic mutation.

This discovery could have implications for human health, Phillips said. Phillips, an assistant professor and the curator of the Genetic Resources Collection at the Natural Science Research Laboratory, said Entpd1, a gene that is expressed in the blood vessels of many species including humans, is uniquely expressed in the salivary glands of vampire bats.

This gene produces molecules in the blood vessels that allow blood to circulate without clotting, he said. If a blood vessel is punctured or cut, the Entpd1 molecules adjacent to the injury retract from the center of the vessel, allowing clotting to occur.

Ordinarily, this clotting process would limit a vampire bat’s ability to get adequate nutrition from its prey. However, unique genetic adaptations allow the vampire bat to release Entpd1 molecules in its saliva.

Because of the evolution of gene expression profiles in the vampire bats’ salivary glands, their saliva acts as a potent anticoagulant, Phillips said. When the bat bites its prey, secretions in the saliva prevent clotting.

Although the host’s cells attempt to retract Entpd1 to begin clotting, the enzyme is replenished by the bat’s saliva, and the blood flow continues, he said.

Phillips said this unique trait is the result of gene recruitment, an evolutionary process in which genes already present in the genome are expressed in a new location in the body.

Vampire bats are the only mammal that feeds exclusively on blood and are the only mammal we know of that uses Entpd1 gene in this manner, Phillips said. They are able to exploit a gene shared among lots of species and use it for a new purpose.

In addition to contributing to general scientific knowledge, Phillips said this type of discovery has potential to advance medical treatments.

Some of the most potent anticoagulants we have identified are derived from proteins found in vampire bats’ saliva. Because these proteins prevent clotting, they may be used to improve stroke victims’ chances of survival, he said. We do not yet know the applications of the genes we looked at in this study, but there is potential to advance medicine through this kind of work.

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