Molecular isolation and characterisation of carp transforming growth factor beta 1 from activated leucocytes

The transforming growth factor (TGF beta) family of proteins are a set of pleiotropic secreted signalling molecules with unique and potent immunoregulatory properties. In this study the molecular cloning of carp TGF beta 1 is reported. A partial cDNA of the TGF beta protein was initially identified from a cDNA pool, obtained by subtracting the cDNAs from Con A-induced carp head kidney leucocytes from uninduced carp head kidney leucocyte cDNA. The entire coding sequence was assembled by sequencing both ends of the cDNA clone by using an anchored PCR reaction. Sequence analysis revealed an ORF encoding a protein of 376 amino acids, containing the similar unique pattern of conserved cysteines (seven out of nine) in the cysteine knot structure which exists in all known TGF beta proteins. Compared with other animal TGF beta s, the cDNA clone shows approximately 59-42, 40-38 and 37-36% amino acid identity with TGF beta 1, TGF beta 3 and TGF beta 2 respectively. Carp TGF beta 1 is expressed at low levels in carp head kidney, spleen, egg and liver, whereas its messenger RNA level is increased after activation of the head kidney leucocytes with Con A. Sequence analysis and pattern of expression suggests that this is the carp TGF beta 1.