Improvement of Animal Welfare Through Transgenic Techniques
The use of transgenic animal models frequently allows the researcher to perform the experiments in a manner that is more consistent with the 3R principles of responsible animal experimentation. This is reflected by the fact that the use of transgenic animals often results in either the lowered degree of experimental severity or the reduction of total numbers of mice that are required to perform the experiments. Regrettably, standard protocols used in the course of generating transgenic mice still rely on a number of surgical procedures that pose a burden to the animals used. One of our goals is to refine transgenic techniques so that they are either more efficient and thus require fewer animals or pose a reduced burden to individual animals.
Transgenic Vasectomy (TgV)
Refinement of multiple transgenic and reproductive techniques
Vasectomy is a surgical procedure (severity level of 2) which until now is indispensable for the preparation of males which are subsequently used to induce pseudopregnancy in foster females. Such females are required for strain rederivation by embryo transfer (ET) as well as other techniques that involve ET such as the production of transgenic and “knock-out” mice. We have recently refined all ET-dependant methods by generating a transgenic mouse strain carrying a dominant male-specific sterility trait. Males from such a strain could be used directly to induce pseudopregnancy in females thus making the vasectomy procedure redundant.
Dominant male sterility was attained by overexpressing a Protamine-1 (Prm1) EGFP fusion protein under the transcriptional and translational regulatory control of Prm1. Male mice from lines showing strong overexpression of the Prm1-EGFP fusion protein displayed complete and dominant male sterility without affecting the ability to mate and to produce copulatory plugs. Conversely the females of the same line remained fertile thus allowing the propagation of the line through mating with wild-type males. Male sterility was due to impaired spermatid maturation affecting sperm viability and motility. The “genetic vasectomy system” was further improved by genetically linking the dominant male sterility to ubiquitous EGFP expression in the soma as an easy phenotypic marker enabling rapid genotyping of transgenic males and females. This double transgenic TgV-EGFP strain represents a reliable and cost-effective “genetic vasectomy” procedure making the conventional surgical vasectomy methodology obsolete.
The latest version of the TgV-EGFP strain is publicly available through the European mouse mutant archive (EMMA) repository.
References:
Figure 1. The dominant, male-sterile TgV-EGFP strain.
A) HA staining of the cross section through the cauda epididymis of wild-type and TgV-EGFP male mice. B) Breeding scheme of the TgV-EGFP strain showing the genetic linkage of the TgV male sterility trait and the full-body EGFP expression over successive generations. C) Typical TgV-EGFP litter. The EGFP positive TgV-EGFP offspring are clearly visible. D) Total number of spermatozoa found in the cauda epididymis of successive generations of TgV-EGFP males.
