MOLECULAR-CLONING AND TISSUE DISTRIBUTION OF PIG TRANSFORMING GROWTH-FACTOR-ALPHA

Transforming growth factor alpha (TGFalpha) was originally identified as a product of tumour tissues and transformed cells in culture. Altho ugh it is now clear that expression of this factor is not restricted t o neoplastic cells, there remains relatively little information about the sites of expression of TGFalpha in normal tissues. Therefore, an a mplified DNA fragment encoding the pig TGFalpha precursor was cloned b y reverse transcription-PCR (RT-PCR) using RNA isolated from normal sk in tissue as the template. Nucleotide sequence analysis predicts a 160 -residue transmembrane polypeptide that differs from the rat, mouse an d human TGFalpha precursors at 14, 15 and six sites respectively. The distribution of TGFalpha mRNA in a wide variety of pig tissues was ana lysed by RT-PCR, using oligonucleotide primers based on the pig TGFalp ha cDNA sequence. TGFalpha transcripts were detected in RNA isolated f rom 17 of the 22 tissues analysed, including four previously unreporte d sites. Using an antibody raised against a synthetic TGFalpha peptide , we have immunolocalized TGFalpha protein to cells within the red pul p of the spleen and to the distal convoluted tubules of the kidney.