Abstract
Left-right (l-r) symmetry breaking and the establishment of asymmetric animal body plan during embryonic development are fundamental questions in nature. The molecular basis of l-r symmetry breaking of snails is a fascinating topic as it is determined by a maternal single handedness-determining locus at a very early developmental stage. This perspective describes the current state of the art of the chiromorphogenesis, mainly based on our own work, i.e. the first step of l-r symmetry breaking, as proven by our "Mechanogenetics", before the start of zygotic gene expression, transfer of chirality information to the cell-fate determining stage, and the expression of nodal at the blastula stage. The Nodal signalling pathway is a common mechanism in vertebrates' chiromorphogenesis in later development. Studies on snails, especially Lymnaea (L.) stagnalis, shall give important insights into the molecular basis of chiromorphogenesis not only in Lophotrochozoa but in vertebrates as well.
Highlights
Chirality is expressed throughout nature, whether microscopic or macroscopic, and whether animate or inanimate
As the species had not been well studied compared with Lymnaea peregra (Freeman & Lundelius, 1982) except for the detailed observation of development (Meshcheryakov, 1990), we studied the breeding behaviour (Hosoiri et al 2003), correlation of cleavage pattern and organismal morphology (Shibazaki et al 2004), cytoplasm injections to the 1-cell embryos of opposite chirality (Kuroda, 2014), cytoskeletal dynamics during spiral cleavages (Shibazaki et al 2004), expression of nodal-Pitx genes (Kuroda et al 2009), creation of mirrorimage healthy animals by twisting blastomeres at the third cleavage (Kuroda et al 2009), etc
When the dextral embryos were treated with actin depolymerization agents, latrunculin A or B, they showed a concomitant absence of spiral deformation (SD) and spindle inclination (SI) (Fig. 1b I left), resembling sinistral embryos (Fig. 1a II)
Summary
Chirality is expressed throughout nature, whether microscopic or macroscopic, and whether animate or inanimate. Most animals appear symmetric externally, but exhibit chirality within the body cavity, i.e. in terms of asymmetric organ position, directional organ looping and lateralized organ function in the larva and adult. Both in animate and inanimate domains, chirality is an excellent approach for studying the link between macroscopic and microscopic phenomena. We constructed backcrossed congenic animals (Hosoiri et al 2003; Kuroda, 2014; Kuroda et al 2009; Shibazaki et al 2004) and carried out positional cloning in order to identify the handedness determining gene(s)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
