When FOXP2 is rendered dysfunctional in humans severe disorders of speech and language can result. As one of the most conserved genes in vertebrates, FoxP2 is also widely involved in a number of important physiological and developmental processes. What drives rapid diversification of the gene remained unknown.

Researchers of joint training program of Chengdu Institute of Biology and Sichuan University, recognized new subtypes of the gene: FoxP2, FoxP2a and FoxP2b. The duplicated FoxP2 genes (FoxP2a and FoxP2b), which were identified in teleosts using synteny and paralogon analysis on genome databases of eight organisms, were probably generated in the teleostspecific whole genome duplication event. A credible classification with FoxP2, FoxP2a and FoxP2b in phylogenetic reconstructions confirmed the teleost-specific FoxP2 duplication.

Heterogeneity in evolutionary rates among clusters consisting of FoxP2 in Sarcopterygii, FoxP2a in Teleostei and FoxP2b in Teleostei reveals asymmetric functional divergence after the gene duplication. Hierarchical cluster analyses of hydrophobicity profiles demonstrated significant structural divergence among the three clusters. The simulated thermodynamic stability variations of the forkhead box domain (monomer and homodimer) showed remarkable divergence in FoxP2, FoxP2a and FoxP2b clusters. Relaxed purifying selection and positive Darwinian selection probably were complementary driving forces for the accelerated evolution of FoxP2 in ray-finned fishes, especially for the adaptive evolution of FoxP2a and FoxP2b in teleosts subsequent to the teleost-specific gene duplication.

The results were published on the free access journal Plos One.