Testicular involution prior to sex change in gilthead seabream is characterized by a decrease in DMRT1 gene...

Area of Science:

• Reproductive biology
• Fish immunology
• Endocrinology

Background:

• Leukocytes play roles in mammalian testes, including immune surveillance and tissue remodeling.
• Seasonal fish testes undergo regression, particularly during sex change.
• The gilthead seabream is a protandrous seasonal teleost fish.

Purpose of the Study:

• To investigate leukocyte presence during the second reproductive cycle (RC) of gilthead seabream.
• To analyze the testicular degenerative process in gilthead seabream, especially before their sex change.
• To understand the role of immune cells in gonadal remodeling.

Main Methods:

• Sampling of gilthead seabream during their second RC.
• Analysis of gonadal development stages using light and electron microscopy.
• Detection of leukocytes (macrophages, B and T lymphocytes, acidophilic granulocytes) via immunocytochemistry and flow cytometry.
• Gene expression analysis of DMRT1 and immune cell markers using PCR.
• Assessment of cell proliferation (BrdU) and apoptosis (DNA fragmentation).

Main Results:

• Gilthead seabream were males in the first two RCs, with testicular degeneration occurring during the second RC.
• Leukocytes, including acidophilic granulocytes, macrophages, and lymphocytes, were present in the testes.
• Acidophilic granulocyte infiltration increased during the later stages of testicular involution.
• DMRT1 gene expression decreased concurrently with testicular degeneration.

Conclusions:

• Innate and adaptive immune cells are present in gilthead seabream gonads.
• A significant testicular degenerative process precedes sex change in gilthead seabream.
• This degeneration is marked by apoptosis, necrosis, immune cell infiltration, and reduced DMRT1 levels.