Hox genes control homocercal caudal fin development and evolution.

Area of Science:

• Evolutionary Biology
• Developmental Biology
• Genetics

Background:

• Ancient bony fishes possessed heterocercal tails, unlike the homocercal tails of modern teleosts.
• The evolutionary transition from heterocercal to homocercal tails in teleosts is not fully understood.
• Hox13 genes are known regulators of posterior identity in animal development.

Purpose of the Study:

• To investigate the role of hox13 genes in teleost caudal fin formation.
• To understand the genetic mechanisms underlying the evolution of homocercal tails.

Main Methods:

• Analysis of zebrafish hox13 gene expression patterns.
• CRISPR/Cas9 gene editing to create hox13 mutant zebrafish.
• Phenotypic analysis of mutant caudal fins.

Main Results:

• Double mutants of hoxb13a and hoxc13a failed to develop caudal fins.
• Single hox13 mutants exhibited heterocercal-like tail morphologies.
• These findings link hox13 gene function to caudal fin evolution.

Conclusions:

• Hox13 genes are essential for caudal fin development in teleosts.
• The evolution of the homocercal tail in teleosts may be linked to the neofunctionalization or subfunctionalization of hox13 duplicates after genome duplication.
• This study provides insights into the genetic basis of a major evolutionary transition in vertebrate morphology.