Molecular characterization of Activin Receptor Type IIA and its expression during gonadal maturation and growth stages in rohu carp.

Activin receptor type IIA (ActRIIA), a transmembrane serine/threonine kinase receptor is an important regulator of physiological traits, viz., reproduction and body growth in vertebrates including teleosts. However, existing knowledge of its role in regulating fish physiology is limited. To address this, we have cloned and characterized the ActRIIA cDNA of Labeo rohita (rohu), an economically important fish species of the Indian subcontinent. Comparative expression profiling of the receptor gene at various reproductive and growth stages supports to its role in promoting oocyte maturation, spermatogenesis and skeletal muscle development via interaction with multiple ligands of transforming growth factor-β (TGF-β) family. The full-length cDNA of rohu ActRIIA was found to be of 1587bp length encoding 528 amino acids. The three-dimensional structure of the intracellular kinase domain of rohu ActRIIA has also been predicted. Phylogenetic relationship studies showed that the gene is evolutionarily conserved across the vertebrate lineage implicating that the functioning of the receptor is more or less similar in vertebrates. Taken together, these findings could be an initial step towards the use of ActRIIA as a potential candidate gene marker for understanding the complex regulatory mechanism of fish reproduction and growth.