Evolutionary lability in Hox cluster structure and gene expression in Anolis lizards

Area of Science:

• Evolutionary Developmental Biology
• Genomics
• Molecular Evolution

Background:

• Hox genes are essential for embryonic axis patterning and are organized in compact clusters.
• Vertebrate Hox gene clusters are conserved, with spacing critical for function.
• Squamate reptile genomes exhibit high variability in transposable elements (TEs), potentially influencing Hox cluster evolution.

Purpose of the Study:

• To investigate the role of transposable elements (TEs) in the evolution of Hox gene clusters in squamate reptiles.
• To determine if TE accumulation in Hox clusters impacts gene expression and developmental processes.
• To test the hypothesis that TEs contribute to evolutionary diversification in lizards and snakes.

Main Methods:

• Performed de novo transposable element (TE) prediction across 17 lizard and snake genomes.
• Quantified TE content within Hox gene clusters and compared it to genome-wide levels.
• Analyzed the age distribution of TEs in Anolis lizards and correlated TE abundance with Hox gene expression patterns.

Main Results:

• Hox clusters generally contain 50% less TE content than the genome-wide average.
• Anolis lizards exhibit unusually high TE content in their Hox clusters, approaching genomic levels.
• Peaks of TE activity in Anolis lizards coincide with speciation events, and high TE content correlates with aberrant Hox gene expression.

Conclusions:

• Transposable elements (TEs) can accumulate in Hox gene clusters, particularly in Anolis lizards.
• TE accumulation in Hox clusters is linked to altered gene expression and may drive evolutionary diversification.
• TEs likely play a significant role in developmental processes and the evolutionary trajectory of squamate reptiles.