Abstract
Transgenic animals play an important role in biomedical research. Their use as animal model is still increasing. Although the process of transgenesis may contribute to refinement of animal use, the application of the biotechnological procedures that are involved in the production of transgenic animals may also cause unexpected, uncontrolled, and
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even undetected animal suffering. Therefore, the aim of the present thesis was to study the effects of the biotechnological procedures involved in genetic modification on the welfare of the resulting offspring. The two most frequently used techniques for inserting new genetic material into the mammalian germ line, pronuclear microinjection and embryonic stem (ES) cell-mediated gene transfer, have been studied. Different groups of mice were generated, each of which had undergone different aspects of the microinjection technique (Chapters 2 and 3) or of the gene targeting technique (Chapters 4 and 5), in order to determine whether the specific manipulations have any effect on the development or behaviour of the progeny. In this way, the effects of microinjection, electroporation, embryo-culture or embryo transplantation on the development of (chimeric) mice could be studied separately. All mice of the different groups were tested in their pre-weaning (0-3 weeks of age) and post-weaning period (4-30 weeks of age) for behavioural and morphological/physiological development and for clinical appearance. Thereafter, post-mortem examinations were performed. In addition, the feasibility of the use of score sheets for monitoring the welfare of transgenic mice, as part of the daily care of animals, has been explored (Chapter 6). With both techniques, the biotechnological procedures increased (perinatal) pup mortality and body weight. In addition, with the gene targeting technique, 8% of the chimeric animals was hermaphrodite. The results so far indicate that, under the present conditions, the biotechnological procedures (microinjection; in vitro culture; embryo transfer) mainly affect the viability of the embryos and seem to have no major effects on the development and behaviour of mice that survive the first 2-3 days after birth. However, before drawing general conclusions, more and different transgenic lines should be studied in a comparable way. A scoring system has been developed, containing a limited number of sensitive, easy to determine and non-invasive parameters, selected from our previous studies on implications of transgenesis for the well-being of mice. The feasibility of this scoring system has been tested, to assess the use of score sheets for monitoring the welfare of transgenic mice on a practical basis, as part of the animal technicians daily routine in a transgenic unit. It has been found to be both practical and useful. Therefore, in the production of transgenic animals, the use of score sheets is recommended, in order to detect both the intended and the non-intended (side) effects of the introduced or mutated gene at an early stage of development.
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