Identification of candidate genes and regulatory mechanisms for thick shank phenotype of Dong Tao chickens.

The Dong Tao Chicken has garnered widespread attention owing to its hallmark trait of remarkably thick shanks. However, the genetic mechanisms and molecular basis underlying this unique phenotype remain largely elusive to date. We carried out crossbreeding trials, performed genome-wide association study (GWAS), and completed transcriptome sequencing of leg tissues. Crossbreeding experiments confirmed that the thick-leg trait of Dong Tao chickens is polygenically controlled. Furthermore, GWAS analysis on the F₂ segregating population screened NAKIN3 as a key candidate gene associated with this trait. Transcriptomic results indicated that tarsometatarsal skin acts as the primary tissue regulating shank circumference growth. Moreover, ACTB was recognized as a core gene driving dermal thickening of the tarsometatarsus. By interacting with IRF family members, TLR4, SOS1, IFNG, STAT family members, EGF and other molecules, ACTB participates in multiple Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways including the Toll-like receptor signaling pathway and cytokine-cytokine receptor interaction pathway to coordinately modulate dermal thickening in the tarsometatarsal skin of Dong Tao chickens. This study identifies key loci and genes governing shank development, offering theoretical basis and genetic resources for dissecting molecular mechanisms and selective breeding of Dong Tao chickens. Nevertheless, these preliminary findings need to be further verified by expanding the experimental population and sample size, together with additional independent validation experiments.