編者按：這是一個很有趣的科學問題,，為什么高等生物器官,，尤其是脊椎生物會出現(xiàn)左右器官不對稱，今天剛剛出版的Nature報道了這個發(fā)現(xiàn)。以前的研究認為Notch信號中的Nodal 基因和胞漿內(nèi)自由鈣是主要決定因素，最新的研究顯示細胞外鈣也是重要的因素,，它能被Notch信號感受，并表達不同的基因,。象為什么大象大而狗小,，為什么有些動物能在水中進行肺呼吸而不缺氧...，這一系列看似簡單的平常問題,，都包含有許多科學道理,。
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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