Developmental proteome dynamics in granulosa and thecal layers from growing follicles to pre-ovulatory duck follicles

Granulosa and thecal layer cells play important roles in the post-hatching follicular growth in laying birds. To examine the biochemical processes of granulosa and thecal layers associated with follicular growth, the technique of data independent acquisition was used in this study to explore protein profiling in granulosa and thecal layers from growing follicles in laying ducks. We identified and quantitatively analyzed 8032 proteins in granulosa cells and 9552 proteins in thecal layer cells. Hierarchical clustering of the resulting profiles revealed differential changes of expression of proteins linked to cell metabolism, signaling, cell junction, especially in steroid synthesis, peroxisome proliferator-activated receptor, and gap junction signaling pathway at different stages of follicles. The highest expression of proteins related to gap junction and peroxisome proliferator-activated receptor signaling pathway occurred in granulosa cells of 3-6 mm or 6-8 mm follicles. In granulosa cells, decreases in the enzymes that catalyze the transformation of estrone into estradiol and proteins related to calcium transport and apoptosis occurred during follicular growth. As follicles grew, proteins related to androgens biosynthesis and involved in gap junction and peroxisome proliferator-activated receptor signaling pathway decreased in the thecal layer cells. Three main group functional clusters extracted from the protein-protein interaction network, were mainly responsible for apoptosis, steroid hormone biosynthesis, and the peroxisome proliferator-activated receptor signaling pathway. These proteomic data provide a holistic framework for understanding how diverse biochemical processes in granulosa cells and thecal layer cells are coordinated at the cellular level during follicular growth in laying birds.