Identification of Chicken Type II Keratin Gene Family Members and Bioinformatics Analysis of Their Functions

Purpose To further explore the molecular characterization and function of the chicken (Gallus gallus) type Ⅱ keratin gene (KRT) family.

Methods The members of the type Ⅱ KRT family were identified from chicken genome data, and their molecular characteristics, chromosome distribution, collinearity within and among species, and molecular function were analyzed by bioinformatics method.

Results A total of 14 chicken type Ⅱ KRTs were identified, all of which were clustered on chromosome 34. The KRT8, LOC107055419, and LOC768978 genes each had two alternative splicing variants. The coding regions of the genes were similar in base composition but different in sequence. The structure of the transcriptional regions, including the number and position of exons and introns, varied among the genes. Collinearity showed that there were no gene fragmentduplications (no collinearity) within the chicken species or between G. gallus and Pavo muticus. However, there were two gene fragment duplications between G. gallus and Meleagris gallopavo; and there was one gene fragment duplication each between G. gallus and Anas platyrhynchos, and between G. gallus and Coturnix japonica, respectively. The chicken type Ⅱ KRTs were all unstable hydrophilic proteins, with highly diverse amino acid compositions and isoelectric points ranging from 5.10 to 8.89. The number of conserved motifs in chicken type Ⅱ KRTs ranged from 9 to 10, including the Filament, Filament superfamily, and Keratin_2_head conserved domains; and their structures were mainly composed of α-helix. Compared to Homo sapiens and Mus muscμlus, chicken had fewer members in the type Ⅱ KRT gene family. Functional analysis indicated that the proteins in this family were involved in biological pathways such as keratinization and intermediate filament formation in the nucleus and cytoplasm, playing a role in the structural integrity of the epidermis and its epidermal appendages.

Conclusion The chicken type Ⅱ KRT gene family shows significant sequence diversity but encodes proteins with similar structures. As major components of the cytoskeleton, these proteins are likely closely related to the growth, development, and structural integrity of chicken feathers.