Mechanisms for pattern formation leading to axis formation and lineage allocation in mammals: A marsupial perspective

Abstract

Developing patterns in early embryogenesis are analysed in conceptuses from several families, including Dasyuridae, Phalangeridae, Macropodidae and Didelphidae, in which cleavage has been examined in some detail. Features common to cleavage and blastocyst formation, and in some cases to hypoblast formation, are used to develop an outline of possible mechanisms leading to axis formation and lineage allocation. Relevant features that have been described only in some species are also included. It is suggested that certain features of marsupial cleavage establish patterns in the developing blastocyst epithelia, pluriblast, trophoblast and hypoblast that contribute to axis formation and lineage a..