蝸殼螺旋的手性（即鏡像不能疊加的一種結構）由一個單一位點在遺傳上決定,，是由母方遺傳的。對此負責的基因一直未被發(fā)現(xiàn),。
Reiko. Kuroda等人發(fā)現(xiàn)，對大蝸牛“靜水椎實螺”（Lymnaea stagnalis）8-細胞階段的胚胎中的細胞進行簡單的操縱,，能夠在成年個體中逆轉手性。而且引人注目的是,，nodal基因（一個在很多物種中賦予左-右非對稱性的基因）的表達也被細胞的重排逆轉。他們還發(fā)現(xiàn),，在手性決定基因（一個或多個）與在促進主導型分裂球排列的第三次分裂時的手性細胞骨架動態(tài)之間有一個強烈的基因聯(lián)系,。這一可以跟蹤的實驗體系的獲得,，將使左-右對稱性的機制比以前更容易研究。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 462, 790-794 (10 December 2009) | doi:10.1038/nature08597
Chiral blastomere arrangement dictates zygotic left–right asymmetry pathway in snails
Reiko Kuroda1,2,3, Bunshiro Endo2, Masanori Abe2 & Miho Shimizu2
1 Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
2 Kuroda Chiromorphology Team, ERATO-SORST, JST, Komaba, Meguro-ku, Tokyo 153-0041, Japan
3 Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
4 Correspondence to: Reiko Kuroda1,2,3 Correspondence and requests for materials should be addressed to R.K.
Most animals display internal and/or external left–right asymmetry. Several mechanisms for left–right asymmetry determination have been proposed for vertebrates1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and invertebrates1, 2, 4, 9, 11, 12, 13, 14 but they are still not well characterized, particularly at the early developmental stage. The gastropods Lymnaea stagnalis and the closely related Lymnaea peregra have both the sinistral (recessive) and the dextral (dominant) snails within a species and the chirality is hereditary, determined by a single locus that functions maternally15, 16, 17, 18. Intriguingly, the handedness-determining gene(s) and the mechanisms are not yet identified. Here we show that in L. stagnalis, the chiral blastomere arrangement at the eight-cell stage (but not the two- or four-cell stage) determines the left–right asymmetry throughout the developmental programme, and acts upstream of the Nodal signalling pathway. Thus, we could demonstrate that mechanical micromanipulation of the third cleavage chirality (from the four- to the eight-cell stage) leads to reversal of embryonic handedness. These manipulated embryos grew to ‘dextralized’ sinistral and ‘sinistralized’ dextral snails—that is, normal healthy fertile organisms with all the usual left–right asymmetries reversed to that encoded by the mothers’ genetic information. Moreover, manipulation reversed the embryonic nodal expression patterns. Using backcrossed F7 congenic animals, we could demonstrate a strong genetic linkage between the handedness-determining gene(s) and the chiral cytoskeletal dynamics at the third cleavage that promotes the dominant-type blastomere arrangement. These results establish the crucial importance of the maternally determined blastomere arrangement at the eight-cell stage in dictating zygotic signalling pathways in the organismal chiromorphogenesis. Similar chiral blastomere configuration mechanisms may also operate upstream of the Nodal pathway in left–right patterning of deuterostomes/vertebrates.
