Editors' ChoiceDevelopment

Modular Morphology

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Science Signaling  10 Jun 2008:
Vol. 1, Issue 23, pp. ec218
DOI: 10.1126/scisignal.123ec218

Developmental genetics data from invertebrate model systems have enabled the description of gene regulatory networks that control cell fate determination during development. It is less clear how these developmental regulatory networks modulate the processes through which specified cells generate morphological form, such as migration and shape change. The primitive chordate Ciona intestinalis has emerged as a model for studying complex morphogenetic events in a system that is similar to vertebrates but morphologically simpler and more experimentally manipulable. Christiaen et al. identified transcriptionally regulated targets of the forkhead box transcription factor FoxF and fibroblast growth factor (FGF) signaling, two components involved in heart development in Ciona. The genetic network involved in heart specification regulated the expression of a subset of genes whose products promote or coordinate cellular processes, such as filipodial extension and adhesion, required for migration of the heart precursor cells. In contrast, many genes encoding other proteins involved in the mechanics of migration appeared to be constitutively expressed. The encoded proteins regulated by the heart genetic network functioned at key points to regulate migration processes independently from one another and from other cellular inputs. This implies a mechanism whereby developmental regulatory networks act as modules that can be added, removed, and shuffled to generate many different combinations of cell behaviors and, therefore, many different morphologies.

L. Christiaen, B. Davidson, T. Kawashima, W. Powell, H. Nolla, K. Vranizan, M. Levine, The transcription/migration interface in heart precursors of Ciona intestinalis. Science 320, 1349-1352 (2008). [Abstract] [Full Text]

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