Gametogenesis regulation and its disturbance in relation to triploidy in cupped oysters, Crassostrea gigas

• Main Author: Maillard, Floriane
• Other Authors: Œstrogènes, reproduction, cancer (OeReCa), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Normandie Université, Christophe Lelong
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2021
• Subjects: Oyster; Triploidy; Spermatogenesis; Cell cycle; Mitosis; Meiosis; Environment; Triploïdie; [SDV.BDLR.RS]Life Sciences [q-bio]/Reproductive Biology/Sexual reproduction; Pacific; Crassostrea gigas
• Online Access: https://theses.hal.science/tel-03709567; https://theses.hal.science/tel-03709567/document; https://theses.hal.science/tel-03709567/file/sygal_fusion_28561-maillard-floriane.pdf

The Pacific cupped oyster, Crassostrea gigas is a successive irregular hermaphrodite bivalve mollusc with an annual and seasonal breeding cycle. Its gametogenetic cycle is strongly influenced by the environment parameters. Most of living species, oysters are naturally diploids (2n). For shellfish aquaculture, triploids oysters (3n) have been developed to obtain sterile animals. Therefore, they exhibit a higher growth by allocating these energy reserves for the growth. But, some studies have shown the ability of a group of 3n oysters (named 3nα) to carry out gametogenesis closed to 2n with numerous proliferating gonial cells and a second group without or with low reproduction potential (named 3nβ) showing an abnormal accumulation of locked germ cells with condensed nuclei. Our study aims to understand the regulations of spermatogenesis in both α and β groups, during mitosis and meiosis events. Thus, our results argue to the deregulation of the germinal lineage and the establishment of the gonadal tract to explain the lower spermatogenesis in 3n oysters. Transcriptomic analysis on the SAC (Spindle Assembly Complex) actors and a proteomic approach reveals the involvement of a cell spindle checkpoint during mitosis and meiosis and of the meiotic homologous recombination in the successful of spermatogenesis in 3nα and disruptions in 3nβ. The spermatogenesis of the 3nα oysters can be explain by epigenetic regulations such as DNA methylation have involved in gene silencing. To conclude, these results provide major data to understand the reproductive regulations of 3nα and β, particularly in the context of global changes, regarding the natural 2n oysters. L'huître creuse du Pacifique, Crassostrea gigas, est un mollusque bivalve hermaphrodite irrégulier successif avec un cycle de reproduction annuel et saisonnier. Son cycle gamétogénétique est fortement influencé par les paramètres environnementaux. Comme la plupart des êtres vivants, les huîtres sont naturellement diploïdes (2n). Pour la conchyliculture, les huîtres ...