Molecular cloning and characterization of Foxp3 in Atlantic salmon (Salmo salar)

Foxp3 is a T cell-specific transcription factor and plays a key role in the development of Treg cells and in the immune regulatory process during inflammation. Here we report cloning and characterization of the full-length cDNA of Atlantic salmon Foxp3, which possesses a Forkhead domain, a zinc finger domain and a leucine-zipper domain as its counterpart in mammals. Foxp3 is highly expressed in thymus. Furthermore, regulated expression was observed in head kidney cells in response to β-glucan and mitogens (LPS and ConA), and in the head kidney, spleen and liver after intraperitoneal injection of live Aeromonas salmonicida. In addition, transfection of CHSE-214 cells with salmon Foxp3 fused with a C-termial RFP tag, resulted in the expression of the transgene in and close to the nuclei upon stimulation. Taken together, these results suggest the presence of a Foxp3 gene in Atlantic salmon that may be an important transcription factor in immune regulation, and further research may reveal the existence of Treg-like T cells in this species.

Research highlights
► Regulatory T cell marker gene Foxp3 of Atlantic salmon is cloned and characterised.
► Foxp3 is highly expressed in thymus.
► Foxp3 mRNA expression is modulated in leukocytes by mitogens and β-glucan.
► Foxp3 mRNA expression is increased in the head kidney after Aeromonas salmonicida infection.
► Transfection of CHSE-214 cells with salmon Foxp3 fused with a C-termial RFP tag, resulted in the expression of the transgene in and close to the nuclei upon stimulation.