Morpho‐regulation in diverse chicken feather formation: Integrating branching modules and sex hormone‐dependent morpho‐regulatory modules

Abstract

Many animals can change the size, shape, texture and color of their regenerated coats in response to different ages, sexes, or seasonal environmental changes. Here we propose that the feather core branching morphogenesis module can be regulated by sex hormones or other environmental factors to change feather forms, textures or colors, thus generating a large spectrum of complexity for adaptation. We use sexual dimorphisms of the chicken to explore the role of hormones. A long-standing question is whether the sex-dependent feather morphologies are autonomously controlled by the male or female cell types, or extrinsically controlled and reversible. We have recently identified core feather branching molecular modules which control the anterior-posterior (BMP, Wnt gradient), medio-lateral (Retinoic signaling, Gremlin), and proximo-distal (Sprouty, BMP) patterning of feathers. We hypothesize that morpho-regulation, through quantitative modulation of existing parameters, can act on core branching modules to topologically tune the dimension of each parameter during morphogenesis and regeneration. Here we explore the involvement of hormones in generating sexual dimorphisms using exogenously delivered hormones. Our strategy is to mimic male androgen levels by applying exogenous dihydrotestosterone and aromatase inhibitors to adult females and to mimic female estradiol levels by injecting exogenous estradiol to adult males. We also examine differentially expressed genes in the feathers of wildtype male and female chickens to identify potential downstream modifiers of feather morphogenesis. The data show male and female feather morphology and their color patterns can be modified extrinsically through molting and resetting the stem cell niche during regeneration.

The Making of a Flight Feather: Bio-architectural Principles and Adaptation

“…This linking occurs via a Velcro-like mechanism to form the closed, coherent surface of the pennaceous feather vane. Basic barb ridge organization allows the flexibility to generate diverse barb branching forms, as seen in different feather types in current birds (Li et al, 2017;Widelitz et al, 2019).…”

Comparison of vertebrate skin structure at class level: A review

“…There are also connexins that can include gap junctions enabling communication between cells. Specifically, Connexin40 is expressed in melanocytes that generate eumelanin and pheomelanin (Inaba et al, 2019; Widelitz et al, 2019).…”

Avian Pigment Pattern Formation: Developmental Control of Macro- (Across the Body) and Micro- (Within a Feather) Level of Pigment Patterns

“…Further, sexual maturation can alter feather morphology, texture, or pigment patterns to attract a mate. The sex hormones indeed determine the feather phenotypes; however, the molecular mechanisms that convert the hormonal signal to feather coloring remain to be elucidated (Widelitz et al, 2019). Neural crest cells (NCCs) delaminate from the dorsal part of the neural tube (NT).…”

“…Administration of estrogen to male chickens can induce a female-specific ASIP expression pattern that causes female-like pigmentation (Oribe et al, 2012). Through sex-hormone regulation, birds can reset feather colors and forms by molting and regenerating new feathers at different life stages (Widelitz et al, 2019).…”