Position-independent and high-level expression of human α-lactalbumin in the milk of transgenic rats carrying a 210-kb YAC DNA

Abstract

The level of expression of transgenes in transgenic animals varies among lines, and is often much lower than that of endogenous genes (position effects). In order to surmount position effects and establish a more efficient production system of transgenic animals producing pharmaceutical proteins in their milk, transgenic rats carrying 210‐kb YAC DNA containing the human α‐lactalbumin gene were produced. Three transgenic lines transmitted the transgene to the next generation. They had one copy of the α‐lactalbumin gene and secreted human α‐lactalbumin in their milk at concentrations of 2.0–4.3 mg/ml. No position effect was seen. The transgene was expressed specifically in the mammary gland of the transgenic rats. The 210‐kb region is thought to contain all the DNA elements required for proper expression of the human α‐lactalbumin gene. The YAC carrying the human α‐lactalbumin gene is a potential vector for the expression of foreign genes in the mammary gland. Mol. Reprod. Dev. 47:157–163, 1997. © 1997 Wiley‐Liss, Inc.

Position-independent and copy-number-related expression of a goat bacterial artificial chromosome α-lactalbumin gene in transgenic mice

“…Transcription units with longer flanking regions were not as efficiently expressed, perhaps indicating that an optimal spatial organization of the transgene rather than the occurrence of dominant cis-regulatory elements is important [19,20]. The 210 kb human αlac YAC seems to contain such elements, as the level of mammary-specific expression was similar in the four available lines carrying one copy of the transgene [8]. Our present study with the 160 kb goat αlac BAC transgene, which behaved similarly to its endogenous counterpart during mammary-gland development and functioning, has confirmed the position-independent expression of large αlac fragments and has shown a linear relationship between the number of integrated copies and the level of expression.…”

Efficient increase of the novel recombinant human plasminogen activator expression level and stability through the use of homozygote transgenic rabbits

“…Therefore, future studies should examine how to control the locus and construct an efficient expression vector in transgenic animals, and how to select expression vectors for specific recombinant proteins, eventually identifying an ideal expression vector and animal species to express different recombinant proteins. The yield must also be further improved by optimization of the expression vector construction or other methods (1)(2)(3)(4)(39)(40)(41)(42)(43).…”

Gene Transfer Strategies in Animal Transgenesis

“…The benefits of artificial chromosome transgenesis will soon be exported to biotechnological applications and, in some cases, have already been foreseen (Fujiwara et al, 1997;Zuelke, 1998Zuelke, , 1999Stinnakre et al, 1999;Rival et al, 2001). These benefits will mostly include the production of recombinant proteins of interest in the mammary gland of transgenic animals, with the hope that animal transgenesis will eventually become more reproducible, efficient, and predictable.…”

“…Soon after the initial success with mice, transgenic pigs were generated for xenotransplantation purposes using a YAC with the entire human membrane-cofactor protein (MCP) gene (Yannoutsos et al, 1995). Next, rabbits (Brem et al, 1996) and rats (Fujiwara et al, 1997) were also shown to be useful for the generation and analysis of transgenic animals with YAC transgenes. In livestock, the benefits of artificial chromosome-type transgenes are expected, fundamentally, in two fields: the already mentioned xenotransplantation projects and the efficient production of recombinant proteins of interest in the milk of transgenic animals through the use of mammary gland-specific genes (Brem et al, 1993;Zuelke et al, 1998;Fujiwara et al, 1999a;Stinnakre et al, 1999;Houdebine, 1994Houdebine, , 2000.…”