Production of transgenic livestock animals bearing antisense growth hormone cDNA and analysis of mechanisms of the transgene expression

点击翻译按钮获取中文摘要

In an attempt to produce transgenic rats bearing antisense DNA complementary to sequences in the rat growth hormone(GH)gege and to investigate whether antisense RNA expression can modulate GH gene expression and body growth , we produced four transgenic founder rats(F_0)by introducing into rat embryos a fusion gene, which consisted of rat GH promoter containing with four copies of thyroid hormone response element(TRE)and antisense cDNA sequences for rat GH.This transgene promoter directed 2.8-fold stimulation of CAT gene expression in transfected GH_3 rat pituitary tumor cells compared with the rat GH promoter alone.Two of four transgenic rats expressed strongly antisense RNA in the pituitary and lymphoid tissues.Transgenicoffspring(F_1)from each founder rat exhibited dwarfism at as early as 3-4 weeks of age, and they exhibited 70-80% reduced growth rate compared with their nontransgenic littermates.We next examined the effects of inserting tandem copies of TRE on tissue-specific expression of antisense GH RNA and modulation of body growth in the transgenic rats.When antisense cDNA for rat GH linked to rat GH promoter alone was introduced into rat embryos, the offspring(F1)of the transgenic fonder rats did not exhibited dwarfism, whereas expression of antisense RNA was detected in their various tissues including pituitary and lymphoid tissues using RT-PCR.From the results, it is suggested that TRE is necessary for the suppression of GH gene expression by antisense RNA.We are now trying to produce a miniature goat by inhibiting GH gene expresion with introduction of antisense goat GH cDNA into pronuclear embryos derived from IVM/IVF oocytes.We have also demonstrated that a 6-kb upstream region of the human transthyretin gene retained all the cis-elements required for developmental, tissue-specific, and quantitatively normal expression.