Data from: Formin is associated with left-right asymmetry in the pond snail and the frog

While components of the pathway that establishes left-right asymmetry have
been identified in diverse animals, from vertebrates to flies, it is
striking that the genes involved in the first symmetry-breaking step
remain wholly unknown in the most obviously chiral animals, the gastropod
snails. Previously, research on snails was used to show that left-right
signaling of Nodal, downstream of symmetry breaking, may be an ancestral
feature of the Bilateria. Here, we report that a disabling mutation in one
copy of a tandemly duplicated, diaphanous-related formin is perfectly
associated with symmetry breaking in the pond snail. This is supported by
the observation that an anti-formin drug treatment converts dextral snail
embryos to a sinistral phenocopy, and in frogs, drug inhibition or
overexpression by microinjection of formin has a chirality-randomizing
effect in early (pre-cilia) embryos. Contrary to expectations based on
existing models, we discovered asymmetric gene expression in 2- and 4-cell
snail embryos, preceding morphological asymmetry. As the formin-actin
filament has been shown to be part of an asymmetry-breaking switch in
vitro, together these results are consistent with the view that animals
with diverse body plans may derive their asymmetries from the same
intracellular chiral elements.