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Different strategies for midline formation in bilaterians

Nature Reviews Neuroscience volume 5, pages 502–510 (2004)Cite this article

Abstract

The evolutionary emergence of the bilateral body plan and the central nervous system required the establishment of a midline organizer. The formation of a solitary, elongated but narrow organizing region for the dorsoventral (or mediolateral) axis requires rather complex molecular interactions. Different modes of midline formation evolved in vertebrates, insects and planarians, indicating that midline formation had a crucial role in the diversification of higher organisms.

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Figure 1: Hypotheses for the transition from radially symmetrical to bilaterally symmetrical animals.
Figure 2: The problem of generating a stripe-shaped organizing region.
Figure 3: Vertebrate solution: midline formation by local elongation owing to a moving organizer.
Figure 4: Formation of a near-Cartesian coordinate system in the chick.
Figure 5: The insect solution: ventral midline formation by repression from a dorsal organizer.
Figure 6: Midline formation in Drosophila melanogaster.
Figure 7: Midline formation by repulsion from a circumventing border: the flatworm solution.

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DATABASES

CnidBase

aristaless

β-catenin

ems

goosecoid

Nkx2.5

Otx

Tcf

Wnt

Entrez Gene

Brachyury

chordin

Gurken

nodal

lefty2

Krox20

pipe

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S2 (simulation)

S3 (simulation)

S4 (simulation)

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Meinhardt, H. Different strategies for midline formation in bilaterians. Nat Rev Neurosci 5, 502–510 (2004). https://doi.org/10.1038/nrn1410

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