A functional study of transforming growth factor-beta from the gonad of Pacific oyster Crassostrea gigas.

ABSTRACT

The transforming growth factor (TGF)-ß superfamily is a group of important growth factors involved in multiple processes such as differentiation, cell proliferation, apoptosis and cellular growth. In the Pacific oyster Crassostrea gigas, the oyster gonadal (og) TGF-ß gene was recently characterized through genome-wide expression profiling of oyster lines selected to be resistant or susceptible to summer mortality. Og TGF-ß appeared specifically expressed in the gonad to reach a maximum when gonads are fully mature, which singularly contrasts with the pleiotropic roles commonly ascribed to most TGF-ß family members. The function of og TGF-ß protein in oysters is unknown, and defining its role remains challenging. In this study, we develop a rapid bacterial production system to obtain recombinant og TGF-ß protein, and we demonstrate that og TGF-ß is processed by furin to a mature form of the protein. This mature form can be detected in vivo in the gonad. Functional inhibition of mature og TGF-ß in the gonad was conducted by inactivation of the protein using injection of antibodies. We show that inhibition of og TGF-ß function tends to reduce gonadic area. We conclude that mature og TGF-ß probably functions as an activator of germ cells development in oyster.