Avian feather development: Relationships between morphogenesis and keratinization

Haake, Anne R.; König, Gerd; Sawyer, Roger H.

doi:10.1016/0012-1606(84)90240-9

Cited by 59 publications

(36 citation statements)

References 35 publications

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“…The developmental steps that form the outer melanin layer and the thin keratin cortex responsible for iridescent colour production are only observed at these very last stages of cellular differentiation (as also observed by [37]). It is unlikely that direct metabolic processes are active at these stages [33,38], and organization should thus instead proceed through entropic, free-energyminimizing interactions, of which we suggest depletion attraction [39] plays a fundamental role. Though the emergence of organized systems through increasing entropy may seem paradoxical, the AsakuraOosawa model of attraction forces resulting from osmotic depletion have been extensively documented in colloidal mixtures [40], and have been shown or suggested to play critical roles in many biological processes [41][42][43].…”

Section: Discussionmentioning

confidence: 95%

“…Also, keratinization is likely associated with the speed at which the feather grows [34,38], potentially explaining previously reported associations between colour and growth bar width [22,28]. The rate of feather keratinization is strongly influenced by the initial amount and concentration of keratin monomers [67], which in turn is mostly limited by keratin gene transcription and mRNA abundance [68].…”

Section: Sexual Selection and The Evolution Of Iridescent Plumagementioning

confidence: 91%

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Nanostructural self-assembly of iridescent feather barbules through depletion attraction of melanosomes during keratinization

Maia

Macêdo

Shawkey

2011

J. R. Soc. Interface.

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Avian plumage colours are model traits in understanding the evolution of sexually selected ornamental traits. Paradoxically, iridescent structural colours, probably the most dazzling of these traits, remain the most poorly understood. Though some data suggest that expression of bright iridescent plumage colours produced by highly ordered arrays of melanosomes and keratin is condition-dependent, almost nothing is known of their ontogeny and thus of any developmental mechanisms that may be susceptible to perturbation. Here, we use light and electron microscopy to compare the ontogeny of iridescent male and non-iridescent female feathers in blue-black grassquits. Feather barbules of males contain a single layer of melanosomes bounded by a thin layer of keratin-producing blue iridescent colour, while those of females contain disorganized melanosomes and no outer layer. We found that nanostructural organization of male barbules occurs late in development, following death of the barbule cell, and is thus unlikely to be under direct cellular control, contrary to previous suggestions. Rather, organization appears to be caused by entropically driven self-assembly through depletion attraction forces that pin melanosomes to the edge of barbule cells and to one another. These forces are probably stronger in developing barbules of males than of females because their melanosomes are (i) larger, (ii) more densely packed, and (iii) more homogeneously distributed owing to the more consistent shape of barbules during keratinization. These data provide the first proposed developmental pathway for iridescent plumage colours, and suggest that any condition dependence of iridescent barbules is likely driven by factors other than direct metabolic cost.

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Section: Discussionmentioning

confidence: 95%

Section: Sexual Selection and The Evolution Of Iridescent Plumagementioning

confidence: 91%

Nanostructural self-assembly of iridescent feather barbules through depletion attraction of melanosomes during keratinization

Maia

Macêdo

Shawkey

2011

J. R. Soc. Interface.

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“…β-keratin in avian scales and feathers showed strong homologies in the protein coding region (Gregg et al, 1984), which suggested that the feather keratin genes may have evolved from scale keratin genes by a single deletion event (Gregg et al, 1984).Like the reptilian scales and avian scales, avian feathers have both β and α-keratins. β-keratin was detected in the feather sheath and barb ridge in feather filaments (Haake et al, 1984;Yu et al, 2002;Chondankar et al, 2003). α-keratin has been reported in the feather sheath and barb ridges of developing feather follicles (Chondankar et al, 2003).…”

Section: Keratinizationmentioning

confidence: 99%

Evo-Devo of amniote integuments and appendages.

Wu¹,

Hou²,

Plikus³

et al. 2004

Int. J. Dev. Biol.

186

185

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Integuments form the boundary between an organism and the environment. The evolution of novel developmental mechanisms in integuments and appendages allows animals to live in diverse ecological environments. Here we focus on amniotes. The major achievement for reptile skin is an adaptation to the land with the formation of a successful barrier. The stratum corneum enables this barrier to prevent water loss from the skin and allowed amphibian / reptile ancestors to go onto the land. Overlapping scales and production of β-keratins provide strong protection. Epidermal invagination led to the formation of avian feather and mammalian hair follicles in the dermis. Both adopted a proximal -distal growth mode which maintains endothermy. Feathers form hierarchical branches which produce the vane that makes flight possible. Recent discoveries of feathered dinosaurs in China inspire new thinking on the origin of feathers. In the laboratory, epithelial -mesenchymal recombinations and molecular mis-expressions were carried out to test the plasticity of epithelial organ formation. We review the work on the transformation of scales into feathers, conversion between barbs and rachis and the production of "chicken teeth". In mammals, tilting the balance of the BMP pathway in K14 noggin transgenic mice alters the number, size and phenotypes of different ectodermal organs, making investigators rethink the distinction between morpho-regulation and pathological changes. Models on the evolution of feathers and hairs from reptile integuments are discussed. A hypothetical Evo-Devo space where diverse integument appendages can be placed according to complex phenotypes and novel developmental mechanisms is presented.

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“…By E19, differentiation of cell shape and keratinization in the neoptile feather is finishing, starting from the tip of the feather (Haake et al, 1984). Nuclei and boundaries of the cells have disappeared in different parts of the feather.…”

Section: Differentiation and Maturationmentioning

confidence: 99%

The biology of feather follicles.

Yu¹,

Yue²,

Wu³

et al. 2004

Int. J. Dev. Biol.

155

133

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The feather is a complex epidermal organ with hierarchical branches and represents a multi-layered topological transformation of keratinocyte sheets. Feathers are made in feather follicles. The basics of feather morphogenesis were previously described (Lucas and Stettenheim, 1972). Here we review new molecular and cellular data. After feather buds form (Jiang et al., 2004), they invaginate into the dermis to form feather follicles. Above the dermal papilla is the proliferating epidermal collar. Distal to it is the ramogenic zone where the epidermal cylinder starts to differentiate into barb ridges or rachidial ridge. These neoptile feathers tend to be downy and radially symmetrical. They are replaced by teleoptile feathers which tend to be bilateral symmetrical and more diverse in shapes. We have recently developed a "transgenic feather" protocol that allows molecular analyses: BMPs enhance the size of the rachis, Noggin increases branching, while anti-SHH causes webbed branches. Different feather types formed during evolution (Wu et al., 2004). Pigment patterns along the body axis or intra-feather add more colorful distinctions. These patterns help facilitate the analysis of melanocyte behavior. Feather follicles have to be connected with muscles and nerve fibers, so they can be integrated into the physiology of the whole organism. Feathers, similarly to hairs, have the extraordinary ability to go through molting cycles and regenerate. Some work has been done and feather follicles might serve as a model for stem cell research. Feather phenotypes can be modulated by sex hormones and can help elucidate mechanisms of sex hormone-dependent growth control. Thus, the developmental biology of feather follicles provides a multi-dimension research paradigm that links molecular activities and cellular behaviors to functional morphology at the organismal level.

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Avian feather development: Relationships between morphogenesis and keratinization

Cited by 59 publications

References 35 publications

Nanostructural self-assembly of iridescent feather barbules through depletion attraction of melanosomes during keratinization

Nanostructural self-assembly of iridescent feather barbules through depletion attraction of melanosomes during keratinization

Evo-Devo of amniote integuments and appendages.

The biology of feather follicles.

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