蝸牛殼的手性（卷繞的方向）是生物學上的一個長期未解之謎?，F(xiàn)在Cristina Grande和 Nipam Patel發(fā)現(xiàn)，蝸牛手性是由一個以其在脊椎動物左-右非對稱性中的作用而知名的基因調(diào)控的,，該基因的名稱為“nodal”,。
多數(shù)動物是兩側對稱的，但在這一框架內(nèi)卻表現(xiàn)出不同程度的左-右非對稱性,。在脊椎動物和其他后口動物中,，導致非對稱性的分子通道會利用信號作用分子Nodal。Grande 和Patel在兩個蝸牛物種中發(fā)現(xiàn)了Nodal的直系同源物（演化上的對應物）及其目標之一Pitx,，還發(fā)現(xiàn)Nodal的失去會中斷蝸牛殼的卷繞,。這表明，“nodal”信號通道對所有兩側對稱動物都是原始的,，并不像人們曾經(jīng)懷疑的那樣是后口動物所特有的,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 457, 1007-1011 (19 February 2009) | doi:10.1038/nature07603
Nodal signalling is involved in left–right asymmetry in snails
Cristina Grande1,2,3 & Nipam H. Patel1,2,3
1 Department of Molecular and Cell Biology,
2 Department of Integrative Biology, and,
3 Center for Integrative Genomics, University of California, Berkeley, California 94720-3200, USA
Many animals display specific internal or external features with left–right asymmetry. In vertebrates, the molecular pathway that leads to this asymmetry uses the signalling molecule Nodal, a member of the transforming growth factor-β superfamily1, which is expressed in the left lateral plate mesoderm2, and loss of nodal function produces a randomization of the left–right asymmetry of visceral organs3, 4. Orthologues of nodal have also been described in other deuterostomes, including ascidians and sea urchins5, 6, but no nodal orthologue has been reported in the other two main clades of Bilateria: Ecdysozoa (including flies and nematodes) and Lophotrochozoa (including snails and annelids). Here we report the first evidence for a nodal orthologue in a non-deuterostome group. We isolated nodal and Pitx (one of the targets of Nodal signalling) in two species of snails and found that the side of the embryo that expresses nodal and Pitx is related to body chirality: both genes are expressed on the right side of the embryo in the dextral (right-handed) species Lottia gigantea and on the left side in the sinistral (left-handed) species Biomphalaria glabrata. We pharmacologically inhibited the Nodal pathway and found that nodal acts upstream of Pitx, and that some treated animals developed with a loss of shell chirality. These results indicate that the involvement of the Nodal pathway in left–right asymmetry might have been an ancestral feature of the Bilateria.
