Transgenesis: Embryo modification to sperm mediated gene transfer

The generation of transgenic animals by conventional transgenic protocols is cumbersome and not very efficient. To improve the efficiency of obtaining transgenic animals, different groups have attempted to genetically modify spermatozoa and these technologies are collectively referred to as sperm mediated gene transfer (SMGT). SMGT technologies involve the modification of either spermatozoa or spermatogonial stem cells that give rise to spermatozoa, followed by either in vitro fertilization or mating with a wild type female to generate transgenic progeny. In addition to the generation of transgenic mice, the use of SMGT technologies has resulted in multiple insights into male reproductive biology. SMGT has bypassed most of the problems associated with the traditional methods of transgenesis and has considerably improved the efficiency of obtaining transgenic animals. Various techniques have been developed by which SMGT can be achieved and this review provides an overview of the evolution of SMGT technology and will indicate how these might be used to further our understanding of mammalian growth and development.