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Animal Biotechnology: Science-Based Concerns
meat and milk composition comparing the products of cloned animals and full siblings evaluating in detail any unanticipated compositional differences, differences in protein quality, or nutrient bioavailability.
Since the donor nuclei used to produce EMS clones are taken from embryonic cells, there is little if any genomic reprogramming needed to drive embryogenesis. However, blastomeres from embryos of more than eight cells, (i.e., from the stages typically used for BNT), must be reprogrammed upon NT (Van Stekelenberg-Hamers et al., 1995; Kono, 1997; Bordignon et al., 2001), since they express a substantial number of genes, including paternal genes, that are not expressed by the oocyte nucleus. Indeed, the nucleus of the mature donor oocyte is transcriptionally quiescent and is associated with a different set of chromatin proteins (e.g., histones) compared to the recipient oocyte nucleus. A similar array of gestational and postnatal abnormalities seen in somatic cell nuclear transfer also has been observed in BNT (Wilson et al., 1995; Garry et al., 1996; Wilmut et al., 1997; Cibelli et al., 1998) clones. To the degree that inadequate or otherwise different reprogramming relative to that occurring normally in gametic nuclei occurs in BNT (De Sousa et al., 1999; Daniels et al., 2000), the composition of food products from NT animals might differ from that of ordinary animals. Although it is difficult to characterize the level of concern without specific data, it seems unlikely that there are changes in gene expression directly related to EMS and BNT cloning procedures that would raise nutritional or food safety concerns. Food products from BNT clones have been consumed by humans, with no apparent ill effects. Based on current scientific understanding, the committee regards products of EMS and BNT clones as posing a low level of food safety concern. Nevertheless, it would seem appropriate that the FDA use available analytic tests to evaluate the composition of food products from animals that themselves result directly from BNT cloning procedures to verify that they fulfill existing standards for animal-derived food products. The products from the offspring of cloned animals were regarded as posing no food safety concern because the animals are the result of natural matings.
The cloning of animals from somatic cells is more recent. Limited sample size and health and production data, as well as rapidly changing cloning protocols, make it difficult to draw conclusions regarding the safety of milk, meat, or other products from somatic cell clones and their offspring. The key scientific issue is whether and to what degree the genomic reprogramming that occurs when a differentiated nucleus is placed into an enucleated egg and forced to drive the development of a clone might result in gene expression that raises food safety concerns. Differences in patterns of developmental gene expression in non-engineered individuals and somatic cell clones would be greatest during early development when reprogramming is incomplete. A number of datasets suggest that the health and wellbeing of neonatal and young somatic cell clones often are impaired relative to those of normal individuals (see Chapter 6