Open AccessNatural loss of function of ephrin-B3 shapes spinal flight circuitry in birds
Author(s) -
Baruch Haimson,
Oren Meir,
Reut Sudakevitz-Merzbach,
Gerard Elberg,
Samantha R. Friedrich,
Peter V. Lovell,
Sónia Paixão,
Rüdiger Klein,
Claudio V. Mello,
Avihu Klar
Publication year - 2021
Publication title -
science advances
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.928
H-Index - 146
ISSN - 2375-2548
DOI - 10.1126/sciadv.abg5968
Subject(s) - natural (archaeology) , function (biology) , loss function , neuroscience , biology , genetics , phenotype , paleontology , gene
Flight in birds evolved through patterning of the wings from forelimbs and transition from alternating gait to synchronous flapping. In mammals, the spinal midline guidance molecule ephrin-B3 instructs the wiring that enables limb alternation, and its deletion leads to synchronous hopping gait. Here, we show that the ephrin-B3 protein in birds lacks several motifs present in other vertebrates, diminishing its affinity for the EphA4 receptor. The avian ephrin-B3 gene lacks an enhancer that drives midline expression and is missing in galliforms. The morphology and wiring at brachial levels of the chicken embryonic spinal cord resemble those of ephrin-B3 null mice. Dorsal midline decussation, evident in the mutant mouse, is apparent at the chick brachial level and is prevented by expression of exogenous ephrin-B3 at the roof plate. Our findings support a role for loss of ephrin-B3 function in shaping the avian brachial spinal cord circuitry and facilitating synchronous wing flapping.