INTRODUCTION AND EXPRESSION OF THE BACTERIAL GLYOXYLATE CYCLE GENES IN TRANSGENIC MICE

The glyoxylate cycle, catalysed by two unique enzymes: isocitrate lyas e (ICL; EC 4.1.3.1) and malate synthase (MS; EC 4.1.3.2), is necessary for the net conversion of acetate into glucose. This metabolic pathwa y operates in microorganisms, higher plants and nematodes. Two bacteri al genes, encoding ICL and MS, were modified in order to introduce the m into the mouse germ line. The ovine metallothionein-Ia (MT-Ia) promo ter-aceB gene-ovine growth hormone (GH) gene (3' GH sequence) construc t was fused to the ovine MT-Ia promoter-aceA gene-ovine GH gene (3' GH sequence). Therefore, in this single DNA sequence, both aceA and aceB are under independent MT-Ia promoter control and can be induced by zi nc. Transgenic mice were generated by pronuclear microinjection of the aceB-aceA gene construct. We now report the establishment of four mou se lines carying these two transgenes. Studies on the progeny of these lines indicate that one line (No. 91) is expressing both genes at the mRNA and enzyme levels in the liver and intestine, whereas another li ne (No. 66) has a much lower expression. Both enzyme activities were d etected in the liver and intestine at levels up to 25% of those measur ed in fully derepressed Escherichia coli cells.