Changes in Hox genes' structure and function during the evolution of the squamate body plan

Area of Science:

• Evolutionary Developmental Biology
• Comparative Genomics
• Vertebrate Embryogenesis

Background:

• Hox genes are crucial for establishing the anterior-posterior body axis in vertebrates.
• Modifications in Hox gene expression correlate with the evolution of vertebrate body plan diversity.
• Reptiles exhibit a wide range of morphological variations, particularly in axial skeleton development.

Purpose of the Study:

• To investigate the genomic organization of Hox clusters in various reptile species.
• To analyze the impact of genomic rearrangements and transposable elements on Hox gene regulation.
• To compare Hox gene expression patterns between species with distinct axial skeletons, like snakes and lizards.

Main Methods:

• Genomic sequencing and analysis of Hox clusters across different reptile taxa.
• Identification and quantification of transposable elements within Hox loci.
• Comparative gene expression analysis (e.g., RNA sequencing) during somitogenesis in corn snakes and whiptail lizards.

Main Results:

• Squamate reptiles (lizards and snakes) possess exceptionally large numbers of transposable elements in their Hox clusters.
• These elements are associated with extensive genomic rearrangements affecting coding and regulatory regions of Hox genes.
• Significant alterations in Hox13 and Hox10 expression were observed during snake somitogenesis, linked to thoracic and caudal region expansion.

Conclusions:

• Genomic rearrangements and transposable element accumulation in Hox clusters are key features of squamate evolution.
• Divergent expression patterns of posterior Hox genes, including sequence and regulatory variations, facilitated morphological radiation in snakes.
• The Hox genetic system demonstrates adaptability in overcoming collinear constraints to generate substantial morphological diversity.