Interspecies transcriptomics identify genes that underlie disproportionate foot growth in jerboas

Area of Science:

• Developmental Biology
• Comparative Genomics
• Evolutionary Biology

Background:

• Vertebrate limb proportions vary greatly, but the genetic basis for individual bone length differences remains largely unknown.
• While skeletal elongation mechanisms are understood, how specific bones achieve disparate lengths across species is unclear.

Purpose of the Study:

• To investigate the genetic and molecular mechanisms underlying the disproportionately long metatarsals in the jerboa compared to the mouse.
• To identify genes and regulatory pathways associated with differential skeletal growth and limb proportion diversification.

Main Methods:

• Comparative transcriptome analysis of homologous growth cartilages from mouse (Mus musculus) and jerboa (Jaculus jaculus).
• Intersection of gene expression differences in metatarsals and forearms between the two species.
• Functional analysis of candidate genes, including Shox2, in mouse limb development models.

Main Results:

• Approximately 10% of orthologous genes showed differential expression linked to jerboa foot elongation.
• Identified novel genes and pathways involved in endochondral ossification and skeletal proportion.
• Discovered that Shox2 gained expression in jerboa metatarsals and is sufficient to promote distal limb elongation in mice.
• Found evidence suggesting de-repression of latent growth potential contributes to jerboa foot elongation.

Conclusions:

• Comparative transcriptomics reveals key genetic regulators of skeletal proportion diversity.
• Shox2 plays a significant role in jerboa metatarsal elongation, highlighting its adaptable function in limb development.
• The findings provide a framework for understanding modular genetic control of skeletal growth and limb morphology evolution.