Abstract

The mesoderm is the region of the embryo that gives rise to muscle, blood and connective tissues; it becomes segregated from the ectoderm and endoderm at gastrulation. Embryological studies have revealed, however, that the potential for certain embryonic cells to become part of the mesoderm is established well before gastrulation, most likely through an extracellular signalling process termed ‘induction’. The recent characterization of mesoderm‐specific mRNAs and proteins now permits an analysis of the very earliest events involved in the specification of the mesoderm at the molecular level. Such experiments should contribute to our understanding of the mechanisms involved in controlling cell differentiation.