Stearoyl-CoA desaturase enzyme converts specific medium- and long-chain saturated fatty acids to their monounsaturated form. Transgenic goats expressing a bovine beta-lactoglobulin promoter-rat stearoyl-CoA desaturase cDNA construct in mammary gland epithelial cells were produced by pronuclear microinjection. The fatty acid composition of milk from 4 female transgenic founders was analyzed on d 7, 14, and 30 of their first lactation. In 2 animals, the expression of the transgene changed the overall fatty acid composition of the resulting milk fat to a less saturated and more monounsaturated fatty acid profile at d 7 of lactation; however, this effect diminished by d 30. In addition, one animal had an increased proportion of the rumen-derived monounsaturated fatty acid C18:1 trans11 converted by stearoyl-CoA desaturase to the conjugated linoleic acid isomer C18:2 cis9 trans11. Milk that has higher proportions of monounsaturated fatty acids and conjugated linoleic acid may have benefits for human cardiovascular health.

Production of transgenic livestock by pronuclear microinjection of DNA into fertilized zygotes suffers from the compounded inefficiencies of low embryo survival and low integration frequencies of the injected DNA into the genome. These inefficiencies are one of the major obstacles to the large-scale use of pronuclear microinjection techniques in livestock. We investigated exploiting the properties of recombinase proteins that allow them to bind DNA to generate transgenic animals via pronuclear microinjection. In theory, the use of recombinase proteins has the potential to generate transgenic animals with targeted changes, but in practice we found that the use of RecA recombinase-coated DNA increases the efficiency of transgenic livestock production. The use of RecA protein resulted in a significant increase in both embryo survival rates and transgene integration frequencies. Embryo survival rates were doubled in goats, and transgene integration was 11-fold higher in goats and three-fold higher in pigs when RecA protein-coated DNA was used compared with conventional DNA constructs without RecA protein coating. However, a large number of the transgenic founders generated with RecA protein-coated DNA were mosaic. The RecA protein coating of DNA is straightforward and can be applied to any species and any existing microinjection apparatus. These findings represent significant improvements on standard pronuclear microinjection methods by enabling the more efficient production of transgenic livestock.

Summary Ten transgenic (sheep metallothionein 1a‐sheep growth hormone transgene, oMt1a‐oGH) homozygous male mice were mated to females of two lines with distinct selection backgrounds. Inter se matings yielded F2 mice in each line: selected background and control background. Genotypes with respect to the transgene insert were obtained in all mice. Weekly body weights were taken. Males were dissected at 8 weeks of age and fat pads and organs were weighed. Females were mated at 10 weeks; reproductive data were collected on the 16th day after detection of a copulatory plug. Gene action on body, fat pads and organs weights showed dominance effects. The oMt1a‐oGH transgene caused body and organ weights to increase and fat pad weights to reduce. No unfavourable effects of the transgene insert were found on reproductive traits. Results indicate that incorporation of the oMt1a‐oGH in populations of mice should be successful. Résumé Dix mâles souris, homozygotes pour le oMt1a‐oGH (mouton métallothionein 1a‐mouton hormone de croissance) ont été accouplés aux femelles de deus lignées avec différents fonds de sélection. Inter se accouplés ont rendu F2 souris dans chaque lignée: sélectionnée et contrôle. Les génotypes en ce qui concerne le transgène ont été mésurés dans tous les souris. Poids corporeles ont été obtenus chaque semaine. Les mâles ont été disséqués à huit semaines; dépôts adipaux et orgues ont été pesés. Les femelles ont été accouplés à dix semaines; données de reproduction ont été assemblés au seizième jour après la détéction d'un tampon de copulation. Dominance a été l'action génique sur le poids corporel, dépôts adipaux et orgues. Le transgène a augmenté les poids corporels et les poids des orgues mais il a réduit les poids des dépôts adipaux. Pas d'effects défavourables on été trouvés dans les caractères reproductives. Les résultats indiquent que l'incorporation du oMt1a‐oGH transgène dans populations de souris pourrai réussir. Zusammenfassung Genwirkung bei oMt1a‐oGH Transgenen in zwei Mäuselinien mit unterschiedlichem Selektionshintergrund Zehn transgene (Schaf Metallothionein 1a‐Schaf Wachstumshormon, oMt1a‐oGH) homozypote Mäuseböcke wurde an Weibchen zweier Linien unterschiedlichen Selektionshintergrundes gepaart. Inter se Paarungen resultierten in F2 Mäusen mit Selektions bzw. Kontrollhintergrund. Alle Genotypen bezüglich des Transgeninserts wurden festgestellt. Gewichte wurden wöchentlich erhoben, Männchen im Alter von 8 Wochen seziert und Fettpolster unf Organgewichte bestimmt. Weibchen wurden im Alter von 10 Wochen gepaart und Reproduktionsdaten am 16. Tag nach Erscheinen des Kopulationspfropfen erhoben. Bei Körper‐, Fettpfropfen und Orangewichten zeigten sich Dominanzwirkungen. Das oMt1a‐oGH Transgen steigert Körper und Organgewichte und reduziert jenes des Fettpfropfens. Es zeigt keine ungünstigen Wirkungen auf Reproduktion, sodaß seine Einführung in Mäusepopulationen erfolgreich sein sollte.

The use of transgenic animals to manipulate milk composition has considerable potential, both for the production of biomedical proteins and for the direct manipulation of milk composition for the improvement of dairy animals and their products (for reviews, see Wall et al. 1992; Yom & Bremel, 1993). Promoters from a number of milk protein genes from a variety of species have been tested for their ability to direct the expression of foreign proteins to the mammary gland (for review, see Maga & Murray, 1995).β-Lactoglobulin (β-lg) is the major whey protein produced in ruminant milk and is part of the normal milk composition of most mammals except humans and rodents (Pervaiz & Brew, 1985). It is expressed at high levels in the mammary gland and is developmentally regulated. Transgenic mice have been produced using the complete ovine (Simons et al. 1987; Shani et al. 1992) and caprine (Ibañez et al. 1997) β-lg genes. In general, high levels of expression were obtained with the ovine β-lg gene, and expression was also seen in a position-independent manner (Whitelaw et al. 1992). Lower levels of expression were reported using the caprine β-lg gene. Here we report the production of transgenic mice using the bovine β-lg gene. We describe high expression, position-dependent, and copy number-related expression of bovine β-lg protein in the milk of six lines of transgenic mice.