Evolution of Emx genes and brain development in vertebrates

Area of Science:

• Evolutionary Biology
• Developmental Genetics
• Comparative Genomics

Background:

• The Emx1 and Emx2 genes play crucial roles in mammalian forebrain development.
• Understanding the evolutionary history of the Emx gene family across vertebrates is essential for comprehending forebrain development.
• Previous studies have established the presence and function of Emx genes in various vertebrate species.

Purpose of the Study:

• To investigate the evolutionary relationships of the Emx gene family within vertebrates.
• To determine the orthology and evolutionary trajectory of Emx genes across diverse vertebrate lineages.
• To clarify the number and ancestral state of Emx genes in the vertebrate lineage.

Main Methods:

• Phylogenetic analysis of Emx gene sequences.
• Comparative sequence analysis of Emx genes from human, mouse, frog, coelacanth, and zebrafish.
• In silico reconstruction of Emx gene evolution.

Main Results:

• Phylogenetic analysis revealed two main clades: Emx1 and Emx2, grouping the respective genes from most investigated taxa.
• The zebrafish Emx1-like gene formed a sister group to both Emx1 and Emx2 clades, indicating significant sequence divergence.
• This divergence suggests either the zebrafish Emx1-like gene is not orthologous to other Emx1 genes, implying three Emx genes in vertebrates, or it has undergone strong diversifying selection.

Conclusions:

• The Emx gene family in vertebrates may consist of three genes, contrary to the previously assumed two.
• The zebrafish Emx1-like gene's unique position highlights potential complexities in vertebrate Emx gene evolution.
• Further research is needed to confirm the orthology and evolutionary history of the zebrafish Emx1-like gene and its implications for vertebrate forebrain development.