Human lymphocytes express hGH-N gene transcripts of 22kDa, 20kDa and minor forms of GH, but not hGH-V gene

Expression of human growth hormone (hGH) in lymphocytes was examined by reverse transcription polymerase chain reaction (RT-PCR) in five normal subjects. Transcripts of hGH-N gene, but not hGH-V gene, were detected. Sequence analysis revealed four kinds of transcripts: 22kDa GH, 20kDa GH and two other forms of variant GH. The 20kDa GH transcript was generated by alternative splicing within exon 3, resulting in a 45bp deletion. One of the variant GH transcripts was also generated by alternative splicing within exon 3, but at a different site, resulting in a 73bp deletion. Because of a frameshift, this variant GH transcript may encode a 6.6kDa protein (truncated GH) that structurally differs from that of 22kDa GH after residue 31. In the other variant GH mRNA, exons 3 and 4 were completely skipped. The proportions of expression of 22kDa GH, 20kDa GH and the truncated GH were 60.9+/-13.6 (+/-S.D.)%, 32.7+/-14.1% and 6.4+/-1.1% (n=5), respectively, by comparative RT-PCR. We conclude that human lymphocytes, like the pituitary gland, express hGH-N gene transcripts of mainly 22kDa GH, but also 20kDa GH and minor variant forms of GH.