Impact of transgenic procedures on behavioral and physiological responses in postweaning mice.

This study evaluates the effects of biotechnological procedures involved in the process of microinjection-induced transgenesis in the mouse by comparing four groups of C57BL/6 mice that differ in their transgenic background (transgenics after integration of a functional corticotropin-releasing factor (CRF) gene construct, transgenics after integration of a nonfunctional CRF gene construct, nontransgenics after transgenic procedures, and controls). These four groups have been tested in various behavioral paradigms. Moreover, the development in growth, morphological characteristics, and clinical appearance of the animals have been recorded from 4 till 30 weeks of age. Differences in behavior, weight gain, and morphology were found between Group 1 (transgenic CRF animals) and Group 4 (control animals). For Group 2 (animals with a noncoding construct) and Group 3 (nontransgenic animals after transgenic procedures), no significant differences from control animals were found. This indicates that, under the present conditions, the biotechnological procedures related to transgenesis (microinjection, in vitro culture, and embryo transfer) have no significant effect on the normal development of the mice in the postweaning period. These results substantiate previous findings on these animals, obtained by screening them in the preweaning period (Days 0-21). However, before general conclusions as to what extent the technique of transgenesis affects the welfare of the animals can be drawn, more and different transgenic lines should be studied in this or a similar way.