Researchers have discovered a new sex hormone in zebrafish which could lead to developing better fertility treatment options for humans.
When the University of Ottawa (Canada) biologists Kim Mitchell and Vance Trudeau began studying the effects of gene mutations in zebrafish, they uncovered new functions that regulate how males and females interact while mating. "Using gene-editing technology set up by our Chinese colleagues, we mutated two related genes and studied the effects on sexual function in zebrafish," Trudeau, wrote in a paper published in the journal Proceedings of National Academy of Sciences.
According to the study, the researchers changed the secretogranin-2 genes through specific mutation and found that it affected the ability of females and males to breed. It severely reduced their sexual behaviour. The fish look normal, but when both sexes are put together, they almost ignore each other!
"Secretogranin-2 is a large protein that is important for the normal functioning of brain cells and other cells that secrete hormones to control body functions such as growth and reproduction. However, this protein can get chopped up by special enzymes and we found that one small fragment called the secretoneurin peptide is important for stimulating sexual function."
"In the genetically altered fish, we can partially restore sexual function by a single injection of the secretoneurin peptide into the body," the researchers said. They believe the peptide acts on cells in the brain and pituitary gland to increase hormone release thereby enhancing the ability of the female to ovulate and lay her eggs.
Normally, within a few minutes after a male and female are introduced for the first time, the male chases the female in a courtship ritual, and shortly therefore they spawn - that is to say, the female releases her eggs to the water, and the male instantly fertilizes them. But the researchers found that only one in 10 of the couples with mutated genes could spawn.
The couples carrying the introduced mutations produce eggs and sperm, but they are simply terrible at mating with each other. This is the first evidence that mutation of these genes leads to the disruption of sexual behaviour in any animal. "We have uncovered new genes that can regulate reproduction, and the secretoneurin peptide is therefore itself a new hormone. The secretoneurin produced in fish is remarkably similar to that found in other animals, including humans," the authors said.
"We can now use our genetically modified fish to look for other factors that could enhance sexual function, be it for increased spawning in cultured fish species, or to help with the search for new human infertility treatments," they noted.