Establishment, conservation, and innovation of dorsal determination mechanisms during the evolution of vertebrate paired appendages

2025/07/05 by M. Brent Hawkins, Sofía Zdral, Silvia Naranjo +10 · 1 voice · 3 citations
Earth and Planetary Sciences · Biochemistry, Genetics and Molecular Biology · #Paleontology and Evolutionary Biology #Developmental Biology and Gene Regulation #Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities

paper · pdf · doi:10.1101/2025.07.02.662459

Abstract

Abstract Limb function requires polarized anatomy across the dorsal-ventral (DV) axis, but it is unclear when the capacity for DV differentiation of paired appendages arose in evolution. Here we define ancestral DV patterning programs in the fins of fishes. We show that the orthologue of the limb dorsal determinant, Lmx1b, is required to establish dorsality in zebrafish pectoral fins and is regulated by a conserved LARM cis-regulatory hub. However, lmx1bb expression in median fins is unaffected by removal of the LARM , suggesting its regulation is an evolutionary innovation specific to the paired appendages. Although we find the LARM is highly conserved across gnathostomes, we identify specific alteration of this region in hillstream loaches, fishes which naturally parallel “double-ventral” fin phenotypes observed in lmx1bb and LARM mutants. Altogether our findings indicate LARM -mediated dorsal identity is an ancestral feature of paired appendages that provide a prepattern for limb evolution and lineage diversification.

Citations

• Zebrafish: Housing and husbandry recommendations

Cited by

• Dorsoventral limb patterning in paired appendages emerged via regulatory repurposing of an ancestral posterior fin module
• Dorsoventral limb patterning in paired appendages emerged via regulatory repurposing of an ancestral posterior fin module. [europepmc]
• Evolutionary pathway and genetic mechanisms of fin-to-limb transition in vertebrates. [europepmc]

Discussions

• We take for granted that our hands have two sides and can articulate in an endless number of ways. But what about a fish’s fin? Can a fish know something “like the back of its fin,” or have its future [bsky, 82 points, 11 comments]

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