title: Differentiation: A central topic in developmental and cell biology.
abstract: The concept of "differentiation" encompasses all processes leading to differently specialized cell types, beginning with the progressive divergence of developmental pathways and ending with the successive programming and final elaboration of each particular cell type. Guidance and positional information are provided by external cues, by differentially allotted cytoplasmic determinants such as mRNA for transcription factors, and by cascades of intercellular signals. Eventually cell type specific selector genes, such as the muscle cell determining MyoD/myogenin genes and neural key genes (e. g., achaete scute-C, neurogenin), are switched on which control entire sets of subordinate effector genes. In multiplying cells "cell heredity" based on an epigenetic cellular memory enables transmission of the cell type determining program from parental to daughter cells. This memory can be based on autocatalytic self-activation of cell type specific selector genes and on the enduring action of gene groups such as the Polycomb and thrithorax complexes that code for proteins which bind to DNA sequences called cellular memory modules. These modules confer permanent accessibility (potentiation) or inaccessibility (silencing) upon many different gene loci on the chromosomes.
authors.affiliation: Department Physiology and Developmental Biology, Zoological Institute, University of Heidelberg, P.O. Box: In Neuenheimer Feld 230, D-69120 Heidelberg, Germany. w.muller@www.zoo.uni-heidelberg.de
authors.forename: W A
authors.initials: WA
authors.lastname: Müller
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic; D015509:Developmental Biology; D018507:Gene Expression Regulation, Developmental; D009024:Morphogenesis; D009124:Muscle Proteins / Q000235:genetics
chemical_list: D009124:Muscle Proteins