Distinct patterns of gene expression within different cells of an embryo are primarily determined by two main events:
Cell Differentiation: As the embryo develops, cells undergo differentiation, where they acquire specific identities and functions. Differentiation involves changes in gene expression, as certain genes are activated or repressed in specific cell types. This process leads to the establishment of distinct patterns of gene expression in different cell lineages.
Cell Signaling and Morphogen Gradients: Cells within an embryo receive signals from their surroundings that influence their gene expression profiles. Morphogens, which are signaling molecules, are often distributed in concentration gradients within the embryo. Cells interpret these gradients and respond by activating or repressing specific sets of genes. The concentration of a particular morphogen at a given location within the embryo can determine the fate of nearby cells, resulting in distinct patterns of gene expression in different regions.
Together, the interplay between cell differentiation and the influence of signaling molecules, such as morphogens, helps establish and maintain the diverse gene expression patterns observed in different cells of an embryo. These events contribute to the development of specialized cell types and the overall organization of tissues and organs during embryogenesis.