Snail spiral DNA discovered
Japanese researchers have edited snail DNA to make their shells spiral the other way around.
Almost all snails' shells coil to the right, but now researchers from the Tokyo University of Science have used CRISPR gene editing technology to make snails with shells that coil the ‘wrong’ way.
The findings are published in the journal Development, and could provide insights into the fundamental basis of left-right asymmetry in animals.
Left-right asymmetry is fairly common across animal evolution, including humans – with a heart usually on the left, for example. However, it is unclear why one type of asymmetry seems to persist.
Japanese researchers now have an answer for one species of freshwater snail (Lymnaea stagnalis) at least.
Successfully applying CRISPR gene editing technology to molluscs for the first time, researchers Masanori Abe and Reiko Kuroda made snails with mutations in a gene called Lsdia1, which had previously been suggested – but not conclusively proven – to be involved in snail shell coiling.
Surprisingly, the researchers could see signs of asymmetry at the earliest possible stage of development – when the snail embryo was just a single cell.
Additionally, the mutant snails could be reared to adults and produced exclusively leftward-coiling offspring.
“It is remarkable that these snails with reversed coiling are healthy and fertile, and that this coiling can be inherited generation after generation (we now have 5th-generation leftward-coiling snails),” Kuroda said.
“Further, these results may have an implication for snail evolution and speciation – given that left- and rightward-coiling snails probably wouldn’t interbreed.”
Given that genes like Lsdia1 are found throughout the animal kingdom, similar mechanisms for controlling left-right asymmetry could be at play in other species – including our own.
There are still details to be worked out.
Lsdia1 might control left-right asymmetry: the gene encodes a formin, a protein that is involved in regulating the cell’s internal skeleton, but more work is needed to understand how this influences the cellular behaviours that control handedness – something the Japanese team is actively working on.
“Although diverse mechanisms have been proposed for different animals, we think a unified mechanism, involving formins and cellular chirality, is probable,” Kuroda said.