A. Palmetshofer et al., SPLICING VARIANTS OF THE HUMAN GROWTH-HORMONE MESSENGER-RNA - DETECTION IN PITUITARY, MONONUCLEAR-CELLS AND DERMAL FIBROBLASTS, Molecular and cellular endocrinology, 113(2), 1995, pp. 225-234
The human growth hormone/human chorionic somatomammotropin (hGH/hCS) g
ene cluster contains five genes: hGH-N, hGH-V, hCS-A, hCS-B, and hCS-L
. In this study, the nature of splicing products of their primary tran
scripts (except hCS-L) was analyzed by nuclease mapping as well as by
reverse transcription-polymerase chain reaction (RT-PCR) experiments.
All the previously described hGH-N mRNAs encoding the normal 22-K grow
th hormone, the 20-K variant as well as a transcript lacking the third
exon were found in pituitary tissue and in transiently transfected hu
man 293-S eels. In addition, splicing products lacking either exons 3
and 4 or exons 2, 3 and 4 were found in both tissues. In accordance to
previously reported data,the hGH-V, the hCS-A and the hCS-B genes whi
ch are expressed in placental tissue give rise to the 22-K mRNA but no
t to 20-K mRNA. Furthermore, no hCS mRNA arising from skipping of exon
3 was present, whereas mRNAs arising from ligation of exon 2 to exon
5 and of exon 1 to exon 5 were clearly detectable. The various hGH cDN
As were expressed in vivo and screened for lactogenic activity. Only t
he 22-K and the 20-K variant were active in this assay. All of the hGH
-N-derived differentially processed RNAs were found in cell lines of l
ymphoid (Hut-78) and of myelomonocytic type (U937), which had been rec
ently described to secrete growth hormone. Interestingly, RT-PCR analy
sis allowed the determination of hGH-N transcripts in dermal fibroblas
ts. This finding underlines the importance of growth hormone in influe
ncing immune system development and further suggests possible autocrin
e/paracrine regulatory loops in skin tissue.