Chicken HOXC8 and HOXC10 genes may play a role in the altered skull morphology associated with the Crest phenotype

• Published in: Journal of experimental zoology. Part B, Molecular and developmental evolution Molecular and developmental evolution, 2023-09, Vol.340 (6), p.392-402
• Main Authors: Tsai, Dien‐Yu, Chen, Jiun‐Jie, Su, Pei‐Chi, Liu, I‐Ming, Yeh, Skye Hsin‐Hsien, Chen, Chih‐Kuan, Cheng, Hsu‐Chen, Chen, Chih‐Feng, Li, Wen‐Hsiung, Ng, Chen Siang
• Format: Article
• Language: English
• Subjects: Crest phenotype; ectopic expression; geometric morphometric analysis; HOX genes; RCAS system
• ISSN: 1552-5007; 1552-5015
• DOI: 10.1002/jez.b.23194

One of the most intriguing traits found in domestic chickens is the Crest phenotype. This trait, characterized by a tuft of elongated feathers sprouted from the head, is found in breeds such as Polish chickens and Silkie chickens. Moreover, some crested chicken breeds also exhibit a protuberance in their anterodorsal skull region. Previous studies have strived to identify the causative factors of this trait. This study aimed to elucidate the role of chicken HOXC8 and HOXC10 in the formation of the Crest phenotype. We explored the effect of ectopic expression of HOXC8 or HOXC10 on the chicken craniofacial morphology using the RCAS retrovirus transformation system. Microcomputed tomography scanning was conducted to measure the 3D structure of the cranial bone of transgenic embryos for geometric morphometric analysis. We found that the ectopic expression of HOXC8 or HOXC10 in chicken heads caused mild morphological changes in the skull compared with the GFP‐transgenic control group. Geometric morphometric analysis showed that HOXC8 and HOXC10 transgenic groups expressed a mild upward shape change in the frontal region of the skull compared with the control group, which is similar to what is seen in the crested chicken breeds. In conclusion, this study supports findings in previous studies in which HOX genes play a role in the formation of the altered skull morphology related to the Crest phenotype. It also supports that mutations in HOX genes may contribute to intra‐ and inter‐specific variation in morphological traits in vertebrates. In this study, we used RCAS retrovirus to overexpress HOXC10 and HOXC8 on the heads of chicken embryos and used CT scans to observe the skulls. Through geometric morphometric analysis, we found that the HOX gene transgenic embryos had more prominent craniofacial features than those in the control group. Research Highlights Mild morphological differences were found between both the RCAS::HOXC8 and RCAS::HOXC10 transgenic chicken groups and the RCAS::GFP transgenic chicken group. The findings supported the hypothesis that both HOXC8 and HOXC10 play a role in the altered skull morphology associated with the Crest phenotype.