Aquaculture Europe 2021

October 4 - 7, 2021

Funchal, Madeira

Add To Calendar 05/10/2021 12:30:0005/10/2021 12:50:00Europe/LisbonAquaculture Europe 2021EFFECTS OF BMP15 KNOCKOUT ON ATLANTIC SALMON GAMETOGENESISCongress AuditoriumThe European Aquaculture Societywebmaster@aquaeas.orgfalseDD/MM/YYYYaaVZHLXMfzTRLzDrHmAi181982

EFFECTS OF BMP15 KNOCKOUT ON ATLANTIC SALMON GAMETOGENESIS

D. Crespo(1)*, E. Kjærner-Semb(1), K. O. Skaftnesmo(1), E. Andersson(1), P. G. Fjelldal(2), T. J. Hansen(2), R. B. Edvardsen(1), R. W. Schulz(1,3), A. Wargelius(1), L. Kleppe(1)

 

(1) Institute of Marine Research, Bergen, Norway

(2) Institute of Marine Research, Matre Research Station, Matredal, Norway

(3) Utrecht University, The Netherlands

E-mail: diego.crespo@hi.no

 



Inducing sterility represents an alternative strategy for sustainable Atlantic salmon (Salmo salar) aquaculture since that can avoid genetic introgression of farmed escapees into wild populations and unwanted precoucius male sexual maturation. One possibility is to target proteins essential for germ cell formation or survival, such as previously identified gonad-specific factors. Bone morphogenetic protein (BMP15) is a critical regulatory factor in mammalian female reproduction that plays a crucial role in ovary development and oocyte maturation, while inactivating mutations in BMP15 result in sterility. Despite its importance in female fertility, little is known regarding the biological function(s) of BMP15/Bmp15 in male gonads in vertebrates. Previous work of our group revealed, as reported in mammalian models, a gonad- and germ cell-specific expression of bmp15 in salmon. To further investigate the role of Bmp15 in gonadal development, we generated in this study bmp15-edited Atlantic salmon using CRISPR/Cas9. Gamete quality analysis showed that fertilized eggs from highly mutated F0 generation bmp15 CRISPR-ed fish had low or no survival, suggesting an important role of Bmp15 in the production of functional gametes, and/or in embryonic development in salmon. However, surviving larvae were kept in order to stablish an F1 generation and to investigate potential phenotypes during gametogenesis. For that purpose, F1 bmp15 knockout (KO) mutants and control fish were reared in a common garden, gonad samples were collected, body weight and length measured and gonado-somatic (GSI) indices scored at 3 different time points (18, 22 and 26 months). At 18 months of age, ~21% of the bmp15 KO females investigated had 1 ovarian bulb only and the majority (83%) of the bmp15 KO males showed germ cell-poor testes, which was accompanied by reduced vasa expression levels compared to the control group in both sexes. In addition, transcripts levels of genes involved in estrogen biosynthesis and signaling (cyp19a1a and esr1) were stimulated in bmp15 KO females. In the following samplings (22 and 26 months of age), no significant difference was recorded for the females in none of the parameters analyzed. In contrast, the stage of spermatogenesis seemed advanced in bmp15 KO males compared to the control group, showing significantly elevated GSI values and higher cumulative frequency of spermiating testes (~50 vs. 22%) but lower expression levels of steroidogenic enzymes (cyp17a1 and star). However, the effect of bmp15 loss-of-function on sperm quality and viability requires further investigation. Taken together, our results suggest that Bmp15 plays a role in the regulation of germ cell development during early stages of both oogenesis and spermatogenesis in salmon, and that genetic ablation of bmp15 in males advances the stage of spermatogenesis but sperm production is normal. Unfortunately, due to the long generation time in female salmon, data on later stages of maturation and ovulation are not available yet and further analysis will have to clarify whether bmp15 loss-of-function leads to obvious ovarian phenotypes as described in mammals.