Transgenic pigs with elevated levels of growth hormone were infertile,
pre-diabetic, and experienced joint problems.
Pig (Sus domesticus).
Pig growth hormone (GH) gene, with expression controlled by either the
human cytomegalovirus (CMV) or mouse leukemia virus (MLV) promoter.
Goal of This Study:
Monitor the development of the transgenic pigs.
Results of This Study:
Transgenic DNA was injected into 1094 one- or two-celled embryos taken from
pigs and then re-implanted in 30 animals. Seventeen of these pigs
maintained their pregnancy and delivered 124 piglets, of which 31
contained the transgene.
The 31 transgenic offspring contained anywhere from 1 to 20 copies of
the transgene, and in one case the transgene had mutated.
Elevated levels of growth hormone (GH) were only detected in the blood
of 3 out of 31 transgenic animals.
The two different promoters used in the study led to very different
patterns of gene expression. In the pig with the CMV promoter, transgene
expression appeared to be localized to the pancreas, while in the pig
with the MLV promoter, transgenic RNA was detected in the pituitary,
stomach, intestine, spleen, and lymph nodes.
The transgenic pigs with elevated GH levels did not gain weight more
rapidly than is typical of non-GM pigs, but their carcassess were much
leaner (5 versus 25 mm of backfat). The pigs also appeared to be infertile
(did not show estrous behavior), had high levels of insulin in their blood
(indicating insulin resistance), and suffered from joint problems.
Ebert, K. M., T. E. Smith, F. C. Buonomo, E. W. Overstrom et al. (1990).
"Porcine Growth Hormone Gene Expression from Viral Promoters in Transgenic
Swine," Animal Biotechnology vol. 1, pp. 145-59.
Tufts University, MA; Monsanto Co., MO; New England Medical Center
Monsanto Co.; Tufts University School of Veterinary Medicine.
Not on the market as of 2009.
Copyright 2009 The Nature