Interspecific Chimeras

Abstract

Several labs have published data using tissue from genetically altered mouse embryos grafted into chick embryos (1–4). The advantages gained from this technique include the ability to analyze the behavior of a population of genetically altered cells among cells with a genetically normal background. In addition, it allows analysis of a particular gene function at stages beyond the normal viability of some strains of homozygous mutant mice. Finally, it provides a marked cell population for study. Two other labs have studied mouse neural crest or neural tube grafts in chick embryos (3,4). Our experience has been with grafting and tracking the cardiac neural crest. This population of cells presents some unique problems because the hosts must be prepared by removal of the endogenous cardiac neural crest. In the absence of the endogenous cardiac neural crest cells, it is imperative that a critical number of grafted mouse neural crest cells migrate into the pharyngeal region and outflow tract or the host embryo develops a severe cardiac outflow-tract malformation that is highly lethal (5). This necessitates extreme care in handling the graft and ensuring that attachment of the graft to the host is rapid.