Lavender or self-blue refers to a

plumage Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...

color pattern in the

chicken The chicken (''Gallus gallus domesticus'') is a domesticated subspecies of the red junglefowl (''Gallus gallus''), originally native to Southeast Asia. It was first domesticated around 8,000 years ago and is now one of the most common and w ...

(''Gallus gallus domesticus'') characterized by a uniform, pale bluish grey color across all

feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and an exa ...

s. The distinctive color is caused by the action of an autosomal recessive gene, commonly designated as "''lav''", which reduces the expression of

eumelanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

and

phaeomelanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

so that black areas of the plumage appear pale grey instead, and red areas appear a pale buff.Crawford, Roy ''Poultry Breeding and Genetics'', Elsevier, 1990

Description

The "lavender" gene (''lav'') in the chicken causes the dilution of both black (eumelanin) and red/brown (phaeomelanin) pigments, so according to color background, dilution due to "lavender" gives a sort of plumage color patterns: On an extended black background, this condition causes the entire surface of the body an even shade of light slaty blue, which is the typical phenotype known as '"self-blue"'. On a red/brown color plumage background, lavender gene degrades color to beige, like in some Pekin Bantams as in the picture set aside. On the color background of the Belgian Bearded d'Uccle Bantams, frequently referred to as the "Mille Fleur" in the United States, lavender causes the pattern known as "porcelain". The resulting "porcelain" pattern is beige with each feather tipped with a V-shaped of slate blue near the end of the feather and the feather tipped with a V-shaped white spangle. Light and

electron microscope An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing it ...

studies have revealed that, although lavender

melanocyte Melanocytes are melanin-producing neural-crest, neural crest-derived cell (biology), cells located in the bottom layer (the stratum basale) of the skin's epidermis (skin), epidermis, the middle layer of the eye (the uvea), the inner ear, vagina ...

s possess relatively normal dendrite morphology, there is defective peripheral accumulation of

melanosome A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotectio ...

s to the dendrites. This results in the patchy transfer of melanosomes into the

keratinocyte Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells. Basal cells in the basal layer (''stratum basale'') of the skin are sometimes referre ...

s of the growing feather. The dilution effect is essentially the result of a mixture of pigmented and unpigmented regions within the feather barbs.

History

The lavender gene was first discovered in the Porcelain variety of Belgian Bearded d'Uccle bantams in 1972,Brumbaugh JA, Chatterjee G, Hollander WF: Adendritic melanocytes: a mutation in linkage group II of the fowl. J Hered 1972, 63:19-25. and verified in 1980. Porcelain colored d'Uccle bantams were around as early as 1909, though the Porcelain variety was not recognized by the

American Poultry Association The American Poultry Association (APA) is the oldest poultry organization in North America. It was founded in 1873, and incorporated in Indiana in 1932. The first American poultry show was held in 1849, and the APA was later formed in respons ...

until 1964. Whether from the Porcelain d'Uccle or other, unknown sources, the lavender gene has been introduced to a number of new chicken breeds over the years, including the Polish and the

Silkie The Silkie, also known as the Silky or Chinese silk chicken, is a Chinese breed of chicken named for its atypically fluffy plumage, which is soft to the touch, like silk or fur. Other unusual qualities include black skin and bones, blue earlob ...

Genetic studies

"Lavender" is an

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the Phenotype, effect of a different variant of the same gene on Homologous chromosome, the other copy of the chromosome. The firs ...

mutation of the chicken affecting the

neural crest The neural crest is a ridge-like structure that is formed transiently between the epidermal ectoderm and neural plate during vertebrate development. Neural crest cells originate from this structure through the epithelial-mesenchymal transition, ...

derived

s. It causes the dilution of both

and

to a light grey or buff, respectively. It has been assigned the symbol ''lav''.Somes, R. G. 1981 ''International Registry of Poultry Genetic Stocks. A Directory of Specialized Lines and Strains, Mutations, Breeds and Varieties of Chickens, Japanese Quail and Turkeys''. Storrs Agricultural Experiment Station, The University of Connecticut, Storrs, Bulletin #460. The ultimate goal of the modern genetic studies is to find out the underlying genes involved in these traits. Lavender in chickens has been found to be a mutation caused by a single base-pair change in

exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence ...

1 of MLPH (melanophilin) gene.Vaez, M., Follett, S.A., Bed’hom, B., Gourichon, D., Tixier-Boichard, M., Burke, T. 2008 A single point mutation within the melanophilin gene causes the lavender plumage colour dilution phenotype in the chicken. BMC Genet. 9:7. In genetic linkage studies, ''Lav'' locus has been assigned to a linkage group known as Cp-R-U group (Creeper-Rose comb-Uropygial). Although Lavender locus is linked to the R ( rose comb) locus by 32.5%, its position has not yet been mapped.

Homologous mutations in other species

Until now, all the reported causal mutations in MLPH (melanophilin) of humans, mice, and other species have been single-base substitutions or small deletions, the effects of which were limited to the dilution of hairMénasché, G., Ho, C.H., Sanal, O., Feldmann, J., Tezcan, I., Ersoy, F., Houdusse, A., Fischer, A., de Saint Basile, G. 2003 Griscelli syndrome restricted to hypopigmentation results from a melanophilin defect (GS3) or a MYO5A F-exon deletion (GS1). J. Clin. Invest. 112:450-456. or feather colour. The MLPH-associated dilution of coat or plumage pigmentation should then result in the defective transport of

s. This produces a diluted, leaden or lavender blue-grey colour and has been reported in several mammals: humans ( Griscelli syndrome type 3), mice, cats, dogs and minks.

In Japanese quail

The lavender phenotype in Japanese quail (''Coturnix coturnix japonica'') is a dilution of both eumelanin and phaeomelanin in feathers that produces a blue-grey colour on a wild-type feather pattern background. Studies of intergeneric hybridization proved that the lavender mutation in quail is homologous to the same phenotype in chickens. In this species, the lavender phenotype is associated with a non-lethal complex mutation involving three consecutive overlapping chromosomal changes (two inversions and one deletion) that have consequences on the genomic organization of four genes (MLPH and the neighbouring PRLH, RAB17 and LRRFIP1). The deletion of PRLH has no effect on the level of circulating

prolactin Prolactin (PRL), also known as lactotropin and mammotropin, is a protein best known for its role in enabling mammals to produce milk. It is influential in over 300 separate processes in various vertebrates, including humans. Prolactin is secr ...

. Lavender birds have lighter body weight, lower body temperature and increased feed consumption and residual feed intake than wild-type plumage quail, indicating that this complex mutation is affecting the

metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

and the regulation of

homeothermy Homeothermy, homothermy, or homoiothermy () is thermoregulation that maintains a stable internal body temperature regardless of external influence. This internal body temperature is often, though not necessarily, higher than the immediate envir ...

In other bird species

In other bird species, similar feather colour dilutions have been described, including the autosomal recessive slate turkey (''

Meleagris gallopavo The wild turkey (''Meleagris gallopavo'') is an upland game bird native to North America, one of two extant species of turkey and the heaviest member of the order Galliformes. It is the ancestor to the domestic turkey (''M. g. domesticus''), w ...

''), milky pigeon ('' Columba livia''), and the lavender muscovy duck ('' Cairina moschata''). It is not yet known which genes are responsible for these dilution mutations in these bird species.

Chicken breeds with "lavender" varieties

Araucana The Araucana () is a breed of domestic chicken from Chile. The name derives from the historic Araucanía (historic region), Araucanía region where it is believed to have originated. It lays blue-shelled eggs, one of very few breeds that do s ...

* Belgian Bearded d'Anvers (Self-blue and Porcelain phases) * Belgian Bearded d'Uccle Bantam * Belgian d'Everberg * Booted Bantam (also called Dutch Booted Bantam) * Dutch Bantam * Old English Game Bantam *

Orpington Orpington is a town in Greater London, England, within the London Borough of Bromley. It is 13.4 miles (21.6 km) south east of Charing Cross. On the south-eastern edge of the Greater London Built-up Area, it is south of St Mary Cray, sou ...

* Pekin (chicken) * Silkie Bantam * Wyandottes, in the UK as recently as 2014

References

{{Reflist, 30em

External links

American Belgian d'Uccle Bantam Club
Chicken plumage patterns Bird colours 1970s in science Mutation