Prodynorphin

Prodynorphin is a opioid polypeptide hormone involved with chemical signal transduction and cell communication. The gene for prodynorphin is expressed in the endometrium and the striatum, and its gene map locus is 20pter-p12. Prodynorphin is a basic building block of endorphins, the chemical messengers in the brain that appear most heavily involved in the anticipation and experience of pain and the formation of deep emotional bonds, and which are also critical in learning and memory.

The gene is thought to influence perception, as well as susceptibility to drug dependence, and is expressed more readily in human beings than in other primates.

Evolutionary implications
Most Asian populations of Homo sapiens have two copies of the gene sequence for prodynorphin, whereas East Africas, Middle Easterners and Europeans tend to have three repetitions. Most humans have multiple copies of the regulatory gene sequence for prodynorphin, which is virtually identical among all primates, whereas other primates have only a single copy.

The extent of regulatory gene disparities for prodynorphin, between human and primates, has gained the attention of scientists. There are very few genes known to be directly related to mankind's speciation from other great apes. According to computational biologist researcher Matthew W. Hahn of Indiana University, "This is the first documented instance of a neural gene that has had its regulation shaped by natural selection during human origins."

The prodynorphin enzyme is identical in humans and chimps, but the regulatory promoter sequences have been shown to exhibit marked differences. "Humans have the ability to turn on this gene more easily and more intensely than other primates. Given its function, we believe regulation of this gene was likely important in the evolution of modern humans' mental capacity," said Hahn.