School of Life Sciences, University of Nottingham, University Park NG7 2RD, UK.
Biol Lett. 2020 Jun;16(6):20200110. doi: 10.1098/rsbl.2020.0110. Epub 2020 Jun 3.
While animal bodies are typically bilaterally symmetric on the outside, the internal organs nearly always show an invariant left-right (LR) asymmetry. In comparison, snails are both internally and externally LR asymmetric, outwardly obvious in the shell coiling direction, or chirality. Although some species of snail are naturally variable for chirality, sinistral individuals occur very rarely in most species. The developmental and genetic basis of these rare mirror-imaged individuals remains mysterious. To resolve this issue, the finding of a 'one in a million' sinistral garden snail called 'Jeremy' was used to recruit citizen scientists to find further sinistral snails. These snails were then bred together to understand whether their occurrence is due an inherited condition. The combined evidence shows that rare sinistral garden snails are not usually produced due to a major effect maternal Mendelian locus. Instead, they are likely mainly produced by a developmental accident. This finding has relevance to understanding the common factors that define cellular and organismal LR asymmetry, and the origin of rare reversed individuals in other animal groups that exhibit nearly invariant LR asymmetry.
虽然动物的身体在外部通常是两侧对称的，但内部器官几乎总是表现出不变的左右（LR）不对称。相比之下，蜗牛在内部和外部都是 LR 不对称的，在外壳卷曲方向或手性上表现得很明显。尽管某些种类的蜗牛在手性上存在自然变异，但在大多数物种中，左旋个体非常罕见。这些罕见的镜像个体的发育和遗传基础仍然是个谜。为了解决这个问题，利用一只名为“杰里米”的罕见左旋花园蜗牛“百万分之一”的发现，招募了公民科学家来寻找更多的左旋蜗牛。然后将这些蜗牛一起繁殖，以了解它们的出现是否是由于遗传条件。综合证据表明，罕见的左旋花园蜗牛通常不是由主要的母系孟德尔基因座产生的。相反，它们可能主要是由发育事故产生的。这一发现对于理解定义细胞和生物体 LR 不对称的常见因素以及在其他表现出几乎不变的 LR 不对称的动物群体中罕见的反转个体的起源具有重要意义。
