Dorsoventral limb patterning in paired appendages emerged via regulatory repurposing of an ancestral posterior fin module.

ABSTRACT: Limbs exhibit adaptive differentiation along their dorsal-ventral (DV) axis, determined by the dorsal expression of the LIM homeobox gene Lmx1b. The paired appendages (ie the pectoral and pelvic fins from which limbs evolved) arose in an early jawless ancestor via co-option of a midline-fin genetic program including modules for anterior-posterior (AP) and proximal-distal (PD) patterning. Unlike the AP and PD axes, median fins lack an unambiguous DV axis, leaving the origin of this DV pattern in paired appendages unresolved. Here, we describe Lmx1b expression in the posterior midline fins of cichlids, sturgeons, catsharks, and lampreys, revealing an ancestral role for this gene predating the origin of paired appendages. In median fins, Lmx1b activation depends on shh from the ZPA, whereas i

SUBMITTER: Zdral S 

PROVIDER: S-EPMC12816808 | biostudies-literature | 2026 Jan

REPOSITORIES: biostudies-literature