8 January 2004

Learning right from left

A central unanswered question in vertebrate embryology is how the initial symmetry of the embryo is broken, and left—right organ asymmetry established. This important step in the development of the body plan is known to involve the Notch signalling pathway, which regulates expression of the Nodal gene. A mathematical model has now been used to identify factors regulating Notch during chick embryo gastrulation. This leads to the identification of transient localized accumulation of extracelluar calcium ions as the source of asymmetric activation of Notch. Free cytosolic Ca²⁺ is important throughout embryonic development. This latest finding suggests that extracellular Ca²⁺ is also important, sensed by Notch and translated into differential gene expression.

Notch activity acts as a sensor for extracellular calcium during vertebrate left-right determination
ÁNGEL RAYA, YASUHIKO KAWAKAMI, CONCEPCIÓN RODRÍGUEZ-ESTEBAN, MARTA IBAÑES, DIEGO RASSKIN-GUTMAN, JOAQUÍN RODRÍGUEZ-LEÓN, DIRK BÜSCHER, JOSÉ A. FEIJÓ & JUAN CARLOS IZPISÚA BELMONTE
Nature 427, 121–128 (2004); doi:10.1038/nature02190
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Developmental biology: Asymmetric fixation
NICK MONK
Computer simulations and laboratory experiments have shed light on how an asymmetric pattern of gene expression is fixed in vertebrate embryos — an early step towards asymmetric development of the internal organs.
Nature 427, 111–112 (2004); doi:10.1038/427111a
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8 January 2004 table of contents