Emergence of a Bilaterally Symmetric Pattern from Chiral Components in the Planarian Epidermis

Most animals exhibit mirror-symmetric body plans, yet the molecular constituents from which they are formed are often chiral. In planarian flatworms, centrioles are arranged in a bilaterally symmetric pattern across the ventral epidermis. Here, we found that this pattern is generated by a network of centrioles with prominent chiral asymmetric properties. We identify centriole components required for establishing asymmetric connections between centrioles and balancing their effects to align centrioles along polarity fields. SMED-ODF2, SMED-VFL1, and SMED-VFL3 affect the assembly of centriole appendages that tether cytoskeletal connectors to position the centrioles. We further show that the medio-lateral polarization of centrioles relies on mechanisms that are partly distinct on the left and right sides of the planarian body. Our findings shed light on how bilaterally symmetrical patterns can emerge from chiral cellular organizations. [Display omitted] •Centrioles form a bilaterally symmetric pattern across the planarian epidermis•Within cells, centrioles are organized into a chiral asymmetric network•ODF2 and VFL1/3 help in establishing asymmetric connections between centrioles•Bilaterally symmetric patterns can emerge from chiral cellular structures This study by Basquin et al. shows that bilaterally symmetric tissue patterns can emerge from chiral cellular structures. Using the planarian flatworm as a model, they describe how the intrinsic chirality of the cytoskeletal network that controls the orientation of epidermal cilia is compensated to achieve bilateral symmetry of the ciliary pattern.