Short stature caused by biologically inactive growth hormone (GH) is characterized by lack of GH action despite high immunoassayable GH levels in serum and marked catch-up growth to exogenous GH administration. We found a heterozygous single-base substitution (A → G) in exon 4 of the GH-1 gene of a girl with short stature, clinically suspected to indicate the presence of bioinactive GH and resulting in the substitution of glycine for aspartic acid at codon 112. We confirmed the presence of mutant GH in the serum using isoelectric focusing analysis. The locus of mutation D112G was found within site 2 of the GH molecule in binding with GH receptor (GHR)/GH binding protein (GHBP). The expressed recombinant mutant GH tended to form a 1:1 instead of the 1:2 GH-GHBP complex normally produced by wild-type GH. The formation of a 1:2 GH-GHBP complex is compatible with the dimerization of GHRs by GH, a crucial step in GH signal transduction. Mutant GH was less potent than wild-type GH not only in phosphorylation of tyrosine residues in GHR, janus kinase 2 (JAK2), and signal transducers and activators of transcription 5 (STAT5) in IM-9 cells, but also in metabolic responses of BaF/GM cells, a stable clone transfected with cDNA of the chimera of the extracellular domain of human GHR, the transmembrane and the cytoplasmic domain of the human thrombopoietin receptor. These results indicate that the D112G mutation in the GH-1 gene causes production of bioinactive GH, which prevents dimerization of GHR and is therefore responsible for the patient's short stature. ( J. Clin. Invest.

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Interferon-a (IFN-a) is a principle cytokine that plays a key regulatory role in mammalian immune systems. The recombinant DNA of IFN-a is composed of the signal sequence region for rice 10 kDa prolamin cDNA, the aminoterminal region of b-glucuronidase DNA, and the mature polypeptide region of human IFN-aDNA, and is expected to produce a biologically active form of IFN-a. This chimerical DNA for coding IFN-a under the control of a cauliflower mosaic virus 35S promoter and a 5Ј-intron of rice cytosolic superoxide dismutase gene (sodcC1), was transformed into dwarf rice by an Agrobacterium-mediated system. Three lines of transgenic rice plant expressing various levels of IFN-a polypeptide were finally generated. The expression level of the recombinant polypeptide in each line was analyzed by an IFN-a antiviral activity assay and enzyme immunoassay. Higher expression of IFN-a was achieved in developing seed endosperm in two of transgenic rice lines. The replacement of the native signal peptide of IFN-a with the prolamin signal peptide was effective for transporting the IFN-a polypeptide into the ER-derived protein body of developing seed endosperm. These results suggest that rice can be used to produce many biologically active mammalian proteins that accumulate in target organelles such as protein bodies.

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