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Tetraspanin Cd9b plays a role in fertility in zebrafish
Sarah Greaves1, Katherine S Marsay1,2, Peter N Monk3
1School of Biosciences, University of Sheffield, Sheffield, United Kingdom.
Abstract:
In mice, CD9 expression on the egg is required for efficient sperm-egg fusion and no effects on ovulation or male fertility are observed in CD9 null animals. Here we show that cd9b knockout zebrafish also appear to have fertility defects. In contrast to mice, fewer eggs were laid by cd9b knockout zebrafish pairs and, of the eggs laid, a lower percentage were fertilised. These effects could not be linked to primordial germ cell numbers or migration as these were not altered in the cd9b mutants. The decrease in egg numbers could be rescued by exchanging either cd9b knockout partner, male or female, for a wildtype partner. However, the fertilisation defect was only rescued by crossing a cd9b knockout female with a wildtype male. To exclude effects of mating behaviour we analysed clutch size and fertilisation using in vitro fertilisation techniques. Number of eggs and fertilisation rates were significantly reduced in the cd9b mutants suggesting the fertility defects are not solely due to courtship behaviours. Our results indicate that CD9 plays a more complex role in fish fertility than in mammals, with effects in both males and females.
Insights
CD9 plays a crucial role in zebrafish fertility, impacting both egg production and fertilization rates. Unlike in mice, CD9 knockout in zebrafish affects both male and female reproductive functions.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Genetics
Background:
- CD9 protein is essential for sperm-egg fusion in mice.
- CD9 knockout mice show no defects in ovulation or male fertility.
- The role of CD9 in fish reproduction is not well understood.
Purpose of the Study:
- To investigate the function of CD9 in zebrafish reproduction.
- To determine if CD9 knockout affects fertility in zebrafish.
- To compare the role of CD9 in fish versus mammalian fertility.
Main Methods:
- Generated cd9b knockout zebrafish.
- Assessed fertility parameters including egg laying and fertilization rates.
- Utilized in vitro fertilization (IVF) to control for mating behaviors.
- Analyzed primordial germ cell numbers and migration.
Main Results:
- cd9b knockout zebrafish exhibited reduced egg laying and fertilization rates.
- Fertility defects were not linked to primordial germ cell number or migration.
- Egg number reduction was rescued by introducing wildtype partners (male or female).
- Fertilization defect was only rescued by using a wildtype male with a cd9b knockout female.
- IVF confirmed reduced egg numbers and fertilization rates in cd9b mutants.
Conclusions:
- CD9 plays a more complex role in fish fertility than in mammals.
- CD9 appears to influence both male and female reproductive functions in zebrafish.
- The study highlights species-specific roles for CD9 in reproduction.
