The development and evolution of left‐right asymmetry in invertebrates: Lessons from Drosophila and snails

Abstract

The unique nature of body handedness, which is distinct from the anteroposterior and dorsoventral polarities, has been attracting growing interest in diverse biological disciplines. Recent research progress on the left-right asymmetry of animal development has focused new attention on the mechanisms underlying the development and evolution of invertebrate handedness. This exploratory review of currently available information illuminates the prospective value of Drosophila and pulmonate snails for innovative new research aimed at elucidating these mechanisms. For example, findings in Drosophila and snails suggest that an actin filament-dependent mechanism may be evolutionarily conserved in protostomes. The polarity conservation of primary asymmetry across most metazoan phyla, which visceral handedness represents, indicates developmental constraint and purifying selection as possible but unexplored mechanisms. Comparative studies using Drosophila and snails, which have the great advantages of using genetic and evolutionary approaches, will accelerate our understanding of the mechanisms governing the conservation and diversity of animal handedness. Developmental Dynamics 237: 3497-3515, 2008.

Far from solved: A perspective on what we know about early mechanisms of left–right asymmetry

“…However, genes are ''agnosic'' with respect to laterality (Morgan, 1991); transcription does not know left from right, and a most interesting aspect of this field concerns the biophysics of how the leftright (LR) axis first becomes oriented with respect to the anterior-posterior and dorsal-ventral axes of the organism (Okumura et al, 2008;Vandenberg and Levin, 2009).…”

Consistent left-right asymmetry cannot be established by late organizers inXenopusunless the late organizer is a conjoined twin

“…While the degree of evolutionary conservation is far from clear (Levin, 2006;Okumura et al, 2008;Schlueter and Brand, 2007), these mechanisms have been worked out in the most detail in Xenopus embryos. The development of normal LR asymmetry in Xenopus embryos requires four specific ion transporters: two H + pumps, V-ATPase (Adams et al, 2006) and H,K-ATPase (Levin et al, 2002), and two K + channels, KvLQT-1 (Morokuma et al, 2008) and K atp (Chen and Levin, 2004).…”

Roles of Motile and Immotile Cilia in Left-Right Symmetry Breaking

“…Finally, to what extent is the mechanism for breaking of L-R symmetry conserved among species? L-R symmetry breaking does not appear to depend on cilia in Drosophila and snail [24]. Further development of various approaches (including genetic, cellular, biophysical, and mathematical) will be necessary to answer these questions.…”