Early Mesoderm formation in the Mouse Embryo

The inaccessibility of the mammalian embryo to experimental manipulation during germ layer formation and early organogenesis, and the awkward geometry of the rodent embryo in particular, have meant that, compared with birds and amphibians, mammals have contributed little to our understanding of mesoderm formation in the vertebrates. Observations on morphology extend back more than 100 years (Snow, 1977) and have been supplemented with more refined investigation with transmission electron microscopy (Batten and Haar, 1979; Poelmann, 1981; Franke et al, 1983), and scanning electron microscopy (Tam & Meier, 1982; Tam et al., 1982; Hashimoto and Nakatsuji, 1989).