(Non)Parallel developmental mechanisms in vertebrate appendage reduction and loss

Area of Science:

• Evolutionary developmental biology
• Comparative genomics
• Vertebrate evolution

Background:

• Appendage reduction and loss are common evolutionary events across diverse vertebrate lineages.
• Phenotypic convergence suggests underlying shared or distinct molecular mechanisms driving appendage loss.

Purpose of the Study:

• To investigate the molecular mechanisms driving appendage reduction and loss in vertebrates.
• To determine if shared genetic pathways or mechanisms underlie convergent appendage loss across distantly related taxa.

Main Methods:

• Comprehensive review of developmental and evolutionary literature concerning appendage reduction and loss.
• Analysis of over a dozen vertebrate genera spanning fish to mammals.

Main Results:

• Appendage reduction and loss are predominantly driven by modified gene expression, rather than alterations in coding sequences.
• The same developmental genes were repeatedly targeted for expression modification across various vertebrate groups.
• Specific mechanisms of gene expression modification were rarely conserved, indicating diverse regulatory routes.

Conclusions:

• Convergent evolution of appendage loss in vertebrates often involves changes in gene expression.
• Adaptive loss-of-function phenotypes can arise frequently through modifications in key developmental gene regulatory networks.