Positional information and pattern formation in development.

A widely used mechanism for pattern formation is based on positional information: cells acquire positional identities as in a coordinate system and then interpret this information according to their genetic constitution and developmental history. In Drosophila maternal factors establish the axes and set up a maternal system of positional information on which further patterning is built. There is a cascade of gene activity which leads both to the development of periodic structures, the segments, and to their acquiring a unique identity. This involves the binding of transcription factors to regulatory regions of genes to produce sharp thresholds. Many of the genes involved in these processes, particularly the Hox complex, are also involved in specifying the body axis and limbs of vertebrates. There are striking similarities in the mechanisms for specifying and recording positional identity in Drosophila and vertebrates.

[1]  P. O’Farrell.  Unanimity waits in the wings , 1994, Nature.

[2]  J. M. W. Slack,et al.  The zootype and the phylotypic stage , 1993, Nature.

[3]  L. Wolpert.  Positional information and the spatial pattern of cellular differentiation. , 1969, Journal of theoretical biology.

[4]  N. Rosenthal,et al.  A transgene target for positional regulators marks early rostrocaudal specification of myogenic lineages , 1992, Cell.

[5]  P. Lawrence.  The making of a fly , 1992 .

[6]  R. Krumlauf,et al.  Hox codes and positional specification in vertebrate embryonic axes. , 1992, Annual review of cell biology.

[7]  P. Bryant,et al.  The polar coordinate model goes molecular. , 1993, Science.

[8]  L. Wolpert.  Positional information revisited. , 1989, Development.

[9]  J. Sanes,et al.  Mammalian muscle cells bear a cell-autonomous, heritable memory of their rostrocaudal position , 1992, Cell.

[10]  Michael Levine,et al.  Binding affinities and cooperative interactions with bHLH activators delimit threshold responses to the dorsal gradient morphogen , 1993, Cell.

[11]  P. Lawrence,et al.  Drosophila segmentation: after the first three hours. , 1993, Development.

[12]  J. Slack.  Inducing factors in Xenopus early embryos , 1994, Current Biology.

[13]  Konrad Basler,et al.  Compartment boundaries and the control of Drosopfiffa limb pattern by hedgehog protein , 1994, Nature.

[14]  S. Cohen,et al.  Interaction between dorsal and ventral cells in the imaginal disc directs wing development in Drosophila , 1993, Cell.

[15]  J. Smith,et al.  Hedgehog, the floor plate, and the zone of polarizing activity , 1994, Cell.

[16]  L Wolpert,et al.  Gastrulation and the evolution of development. , 1992, Development (Cambridge, England). Supplement.

[17]  S. Carroll,et al.  Gene regulation in two dimensions: the proneural achaete and scute genes are controlled by combinations of axis-patterning genes through a common intergenic control region. , 1992, Genes & development.

[18]  S. DiNardo,et al.  Drosophila hedgehog acts as a morphogen in cellular patterning , 1994, Cell.

[19]  J. Smith,et al.  Responses of embryonic xenopus cells to activin and FGF are separated by multiple dose thresholds and correspond to distinct axes of the mesoderm , 1992, Cell.