HGH isoforms: cDNA expression, adipogenic activity and production in cell culture.

We have isolated, cloned and achieved functional expression of the cDNAs for both 22 kDa and 20 kDa human growth hormone (hGH) isoforms. A selective cDNA cloning strategy was used to preferentially and simultaneously obtain both hGH 22 kDa and hGH 20 kDa cDNAs. These were used to construct minigenes which were subcloned into two eukaryotic expression vectors and then introduced transiently in COS-7 cells and stably into CHO cells in culture. Transfection assays in COS-7 cells of both minigenes allowed the detection of the secreted hGH 22 kDa and hGH 20 kDa. These hGHs isoforms secreted into COS-7 medium were able to specifically promote differentiation of 3T3-F442A preadipocytes to adipose cells. Adipocyte differentiation was quantitated by Oil Red O triacylglycerol staining or glycerophosphate dehydrogenase activity. Furthermore, stable CHO cell lines have been derived that produce these hGH isoforms.