Researchers discover new sex hormone .
- SIGMABIOL
- Jul 11, 2020
- 2 min read
The new hormone that stimulates sexual functions in fish could lead to novel infertility treatments in humans.
When University of Ottawa 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.
WHAT WAS THE PROJECT?
Kim and I were working with international collaborators from the Institute of Hydrobiology at the Chinese Academy of Sciences in Wuhan. Using gene-editing technology set up by our Chinese colleagues, we mutated two related genes and studied the effects on sexual function in zebrafish. They are freshwater fish belonging to the carp and minnow family that are now a widely used model organism in biomedical research.
WHAT DID THEY DISCOVER?
We changed the secretogranin-2 genes through specific mutations and found that it affected the ability of females and males to breed. It severely reduced their sexual behavior.
The fish look normal, but when both sexes are put together, they almost ignore each other!
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 we 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 disruption of sexual behaviour in any animal
WHAT ROLE SECRETOGRANIN-2 PLAYS?
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. We 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.
SUMMARY:-
The secretory granule protein secretogranin-2 is processed to the bioactive neuropeptide secretoneurin. While these are expressed in hypothalamic neurons and anterior pituitary cells, a role in hormonal control of reproduction is unknown. We provide in vivo evidence that secretogranin-2 plays a critical role in fertility regulation. Mutation of the secretogranin-2a and -2b genes in zebrafish leads to disrupted sexual behaviors, reduced ovulation and egg-laying, and suboptimal fertility and embryo survival. Injection of a synthetic secretoneurin peptide enhanced reproductive outcomes in the mutant fish. Our secretogranin-2 mutants offer an amenable model system in which to screen potential injectable stimulators of reproduction, be they for spawning in cultured fish species or to help with the search for new human infertility treatments.
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