Mammalian chimaeras / Anne McLaren.

  • Anne McLaren
Date:
[1976]
Catalogue details
    17/168 (page 7)
    Uses of chimaeras 7 son, 1974) and rabbits (Gardner & Munro, 1974; Moustafa, 1974), and chi- maeric rats have been made by the aggregation method (Mayer & Fritz, 1974; R. J. Mullen, personal communication). No problems have been encountered in inducing aggregation between cleaving embryos of different strains, or even of different rodent species. Mouse-rat aggregation chimaeras develop successfully to the blastocyst stage (Mulnard, 1973; Stern, 1973; Zeilmaker, 1973), and cells from both species can be seen contributing to both inner cell mass and trophoblast. The dual origin of the trophoblast might be expected to interfere with the implantation process in either mouse or rat uteri, since blastocysts of neither species are able to implant normally in the uterus of the other (Tarkowski, 1962), and indeed no successful post-implantation development of mouse-rat aggregation chimaeras has been reported. Using the mouse-bank vole com¬ bination, Mystkowska (1975) attempted to produce aggregation chimaeras with trophoblast of entirely mouse origin by sandwiching one bank vole embryo between two mouse embryos. After transfer to a mouse foster-mother, some of the chimaeric embryos continued to develop for a few days, though morphological abnormalities were seen. The most successful between-species experiments have been those of Gardner & Johnson (1973), using the injection technique to introduce rat inner cell masses into mouse blastocysts, before transfer to mouse foster- mothers. Evidence of the composite origin of embryos up to the egg cylinder stage (7 days of gestation) was obtained by treating alternate sections with fluorescent anti-rat and anti-mouse immune sera. Electrophoretic examina¬ tion of later stages for enzyme markers suggested that the rat component decreased in amount towards the end of gestation (M. H. Johnson, personal communication). No proven chimaeras have as yet survived beyond birth. Uses of chimaeras This book will be mainly concerned with two types of experimental study for which chimaeras provide uniquely suitable material. The first belongs to the field of experimental embryology, making use of the two cell populations to trace the origin and fate of tissues and cell lineages in development, as earlier embryologists used cell populations marked with vital dyes. The second is an aspect of developmental genetics, and seeks to analyse how genetically different cells collaborate to form an adult animal. Although the distinction between the two approaches is often blurred. Chapters 3 and 4 will concentrate on the experimental embryology aspects, and Chapters 5 to 9 on developmental genetics. The construction of 'fate maps', and the clonal analysis of development, have been pursued in an elegant manner in insects, especially Drosophila, using genetic mosaics rather than chimaeras (see for example Hotta & Benzer,