A new spin on handed asymmetry

Article Abstract:

Most vertebrate internal organs develop asymmetrically with regard to the body's midline, but questions are raised about how the early bilateral symmetry of the embryo is broken so that the L-R axis is always oriented the same way. Nonaka and colleagues have shown that an anticlockwise rotation of cilia is used by the mouse node to create extraembryonic fluid directional flow. It is proposed that such nodal flow focuses significant L-R determinants to one sie of the node, activating distinctive signalling pathways on each side of the embryo.

Observations, Symmetry (Biology)

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BMP signalling specifies the pyloric sphincter

Article Abstract:

It has been established that signalling by bone morphogenetic protein (BMP) from the avian small intestine prompts the cells of the neighbouring gizzard primordium to form a sphincter. This research provides new information about the processes by which new cell fates are determined at the borders between separate embryological domains. BMP signalling is significant in the regionalization of the gut, specifying the sphincter at its correct location to function as a gate between the gizzard and intestine.

Morphogenesis, Cell transformation

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Legs to wings and back again

Article Abstract:

Molecular clues to the biological problem of how arms or wings become different from legs have been provided by Takeuchi and colleagues and Rodriguez-Esteban and colleagues. They shows that Tbx5 and Tbx4, transcription factors expressed in the developing forelimb and hindlimb, control the identity of arms and legs. Misexpression of Tbx5 in the chick embryonic hindlimb results in a leg that looks like a wing, and misexpression of Tbx4 in the wing region leads to the formation of leg-like structures.

Abnormalities, Extremities (Anatomy)

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