Sexually Dimorphic Sail Feathers in the Mandarin Duck: A Model for Lifelong Developmental Modulation [ChIP-seq]

Developmental processes extend beyond embryogenesis to support lifelong tissue adaptations. Avian feather follicles, with their resident stem cells and capacity for cyclic regeneration, provide a dynamic model for postnatal tissue remodeling. Here, we propose the Mandarin duck (Aix galericulata) as an ideal model to study lifelong developmental modulation, focusing on the sexually dimorphic “sail feather”—a secondary flight feather in males that undergoes seasonal transformation into a strikingly asymmetric, ornamented phenotype during the breeding season. We identified asymmetric morphogen expression in regenerating male sail feathers and used transcriptome and H3K27ac ChIP-seq to uncover male and female signaling pathways and regulatory elements. Comparative epigenomic profiling reveals enriched estrogen receptor binding motifs in females. Hormone profiling shows seasonal variation, with a marked rise in female estrogen levels preceding the mating season. These results imply Mandarin duck sail feathers integrate local morphogenetic programs, epigenetic regulation, and systemic hormonal cues to orchestrate sexually dimorphic and seasonally dynamic feather morphogenesis. This work establishes a framework for further mechanistic study of the interplay between regeneration, regional identity, and hormonal plasticity in a vertebrate integumentary system. Overall design: We profiled active regulatory elements in Mandarin duck (Aix galericulata) feather follicles using H3K27ac ChIP-seq during early regenerative growth in the breeding season (“in season”). Two body regions were compared: the sexually dimorphic sail feather (remex 12) and the adjacent secondary flight feather (remex 11). For males, we collected regenerating sail feathers that contain lateral blue and medial brown vanes (“blue+brown sail feather”; 2 biological replicates) and regenerating flight feathers with the same vane composition (“blue+brown flight feather”; 2 biological replicates). For females, we collected regenerating sail feathers characterized by dark/black pigmentation (“black sail feather”; 2 biological replicates) and regenerating flight feathers with blue and black pigmentation (“blue+black flight feather”; 2 biological replicates). In total, eight H3K27ac ChIP libraries (2 reps × 4 conditions) were generated; samples were processed in parallel with identical protocols to enable differential analyses by sex and by region (sail vs. flight).