Introduction to provocative questions in left–right asymmetry

Abstract

Left–right asymmetry is a phenomenon that has a broad appeal—to anatomists, developmental biologists and evolutionary biologists—because it is a morphological feature of organisms that spans scales of size and levels of organization, from unicellular protists, to vertebrate organs, to social behaviour. Here, we highlight a number of important aspects of asymmetry that encompass several areas of biology—cell-level, physiological, genetic, anatomical and evolutionary components—and that are based on research conducted in diverse model systems, ranging from single cells to invertebrates to human developmental disorders. Together, the contributions in this issue reveal a heretofore-unsuspected variety in asymmetry mechanisms, including ancient chirality elements that could underlie a much more universal basis to asymmetry development, and provide much fodder for thought with far reaching implications in biomedical, developmental, evolutionary and synthetic biology. The new emerging theme of binary cell-fate choice, promoted by asymmetric cell division of a deterministic cell, has focused on investigating asymmetry mechanisms functioning at the single cell level. These include cytoskeleton and DNA chain asymmetry—mechanisms that are amplified and coordinated with those employed for the determination of the anterior–posterior and dorsal–ventral axes of the embryo. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’.

Left-right asymmetry in firing rate of extra-retinal photosensitive neurons in the crayfish

“…Crayfish use their limbs during aggression; asymmetries of limb performance could affect this behavior (Angilletta and Wilson 2012). Levin et al (2016) have suggested that left and right asymmetries in organisms arise from embryogenesis. 6 th AG develops from two embryonic neuromeres in the crayfish Procambarus clarkii (Kondoh and Hisada 1986;Mulloney et al 2003), and the CPR-axons are in the ventral cord, in Wiersma area 82 for the left hemicord, and in area 79 of the right hemicord of the cord map of the crayfish (Hermann 1972).…”

Revealing chiral cell motility by 3D Riesz transform-differential interference contrast microscopy and computational kinematic analysis

“…Left–right asymmetry is a fundamental property that is widely observed across species, such as in the position of visceral organs and lateralized brain functions 1 , 2 . Despite a significant influence of left–right asymmetry on the body plan, its precise phenomenon, underlying molecular mechanisms and functional roles in the organisms still remain unclear 3 . With regard to the initial symmetry-breaking step, it was postulated that the molecular handedness or chirality is converted to a cellular and multicellular asymmetry that finally leads to left–right asymmetry in the organisms 4 .…”

Asymmetric Firing Rate from Crayfish Left and Right Caudal Photoreceptors Due to Blue and Green Monochromatic Light Pulses

“…Left-right asymmetry is a characteristic of the brain from vertebrate species and some invertebrate species [24], which arises from embryogenesis in the organism [25][26][27]. Crustacean decapods showed the left and right asymmetry in some anatomical regions [28][29][30].…”