Allende, Miguel L2024-10-142024-10-142024-01-19Cumplido N, Arratia G, Desvignes T, Muñoz-Sánchez S, Postlethwait JH, Allende ML. Hox genes control homocercal caudal fin development and evolution. Sci Adv. 2024 Jan 19;10(3):eadj5991. doi: 10.1126/sciadv.adj5991. Epub 2024 Jan 19. PMID: 38241378; PMCID: PMC10798566https://hdl.handle.net/1808/35580Ancient bony fishes had heterocercal tails, like modern sharks and sturgeons, with asymmetric caudal fins and a vertebral column extending into an elongated upper lobe. Teleost fishes, in contrast, developed a homocercal tail characterized by two separate equal-sized fin lobes and the body axis not extending into the caudal fin. A similar heterocercal-to-homocercal transition occurs during teleost ontogeny, although the underlying genetic and developmental mechanisms for either transition remain unresolved. Here, we investigated the role of genes in caudal fin formation as these genes control posterior identity in animals. Analysis of expression profiles of zebrafish paralogs and phenotypes of CRISPR/Cas9-induced mutants showed that double and mutants fail to form a caudal fin. Furthermore, single mutants display heterocercal-like morphologies not seen since Mesozoic fossil teleosteomorphs. Relaxation of functional constraints after the teleost genome duplication may have allowed duplicates to neo- or subfunctionalize, ultimately contributing to the evolution of a homocercal tail in teleost fishes.Copyright © 2024 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly citedhttps://www.ncbi.nlm.nih.gov/pmc/about/copyright/Article10.1126/sciadv.adj599138241378openAccess