Identification of Genes Associated with Crest Cushion Development in the Chinese Crested Duck

SIMPLE SUMMARY: The crest cushion is a phenotypic appendage observed in most birds, and its appearance differs according to the species. However, the mechanism underlying the formation of the crest cushion and the changes in the expression of the associated genes during development has not been elucidated. We aimed to study the differential expression of selected genes in the Chinese crested duck to assess the genes involved in crest cushion formation and their expression. Our results show that the expression of genes belonging to the homeobox family was significantly altered during the various developmental stages, highlighting their role in the development of the crest cushion. This study elucidated a method to assess the molecular mechanism involved in the formation of the crest cushion and to assess the changes in the gene expression at the genome level. ABSTRACT: The crest trait is a specific and widely distributed phenotype in birds. However, the shape and function vary in different species of birds. To understand the mechanism of crest formation, the present study used RNA sequencing and weighted gene co-expression network analysis (WGCNA) to identify the crest-cushion-associated genes in the Chinese crested (CC) duck. As a result, 28, 40, 32, 33, and 126 differentially expressed genes (DEGs) were identified between CC and cherry valley (CV) ducks at the embryonic days (E)15, E22, E28, D7 (7 days old), and D42 stages, respectively. In addition, the results of WGCNA show that 3697 (turquoise module), 485 (green-yellow module), 687 (brown module), 205 (red module), and 1070 (yellow module) hub genes were identified in the E15, E22, E28, D7, and D42 stages, respectively. Based on the results of DEGs and WGCNA Venn analysis, three, two, zero, one, and seven genes were found to be associated with crest cushion formation at the E15, E22, E28, D7, and D42 stages, respectively. The expression of all the associated genes and some DEGs was verified by real-time quantitative polymerase chain reaction. In conclusion, this study provided an approach revealing the molecular mechanisms underlying the crested trait development.