|Year : 1990 | Volume
| Issue : 5 | Page : 364-366
Study of inheritance of depigmentation of dog's muzzle
K G Shah
Source of Support: None, Conflict of Interest: None
A new animal model system was developed using dog's muzzle to demonstrate genetic transmission of depigmentation. Dog's muzzle is 'black in colour and heavily pigmented with pigement melanin. This study provides cluse to the genetic transmission of depigmentation. The genetic transmission of depigmentation of dog's muzzle was autosomal dominant.
Keywords: Inheritance, Depigmentation, Dog′s Muzzle
|How to cite this article:|
Shah K G. Study of inheritance of depigmentation of dog's muzzle. Indian J Dermatol Venereol Leprol 1990;56:364-6
The melanocyte is one of the well studied cells of the mammal yet the inheritance of depigmentation in humans is not properly understood. The application of experimental techniques to animal models has helped to some extent in unraveling the etiology of vitiligo. A striking example of depigmentation that resembles the vitiligo of humans is amelanosis in the Dam chicken. These chickens have black feathers shortly after being hatched. At about six weeks of age, the feathers begin to turn white. Eventually, the chickens become totally white. This disorder is inherited as a polygenic trait'. In this study dog's muzzle was used as an experimental animal model to find out the exact inheritance of depigmentation. No such study is available in the literature.
| Material and methods|| |
The nose, facial portion of the respiratory system and the anterior portions of the upper and the lower jaws collectively constitute the muzzle. Dog's muzzle was used as an experimental animal model to demonstrate genetic transmission of depigmentation. Dog's muzzle is very heavily pigmented due to the pigment melanin and black in colour. So it was used as an experimental animal model to study genetic inheritance of depigmentation. A one year old female mongrel street dog with depigmented patches on the muzzle and depigmented mucous membrane of the mouth was domesticated [Figure - 1]. She was mated to a male street dog of known ancestry but from different family without any depigmentation of the muzzle and mucous membrane. His father and mother were having normal pigmented muzzles. The pedigrees were studied for four generations for a period of ten years.
| Results|| |
Results are shown in pedigree chart [Figure - 2]. It is evident that both sexes of all the generations are affected in the vertical transmission. The depigmented muzzle offspring appears in every generation, with no 'skipping.' The character is transmitted by 1-2 to approximately half her offsprings on the average. Unaffected offsprings do not transmit the trait to their offsprings. The occurrence and transmission of the depigmentation of the muzzle are not influenced by sex. Male to male transmission is present. Inbreeding of affected dogs 11-3 and 11-4 resulted in five offspring, two of which 111-12, 111-15 showed depigmented muzzle. Consanguineous mating of normal dog 11-4 and 11-5 resulted in two normal offsprings 111-16 and 111-17. The depigmentation of the muzzle of one of the affected pups is shown in [Figure - 3]. [Figure - 4] shows five pups of which central three pups are having depigmented muzzles and other two are having normal pigmented muzzles.
This experiment of inheritance of depigmentation of dog's muzzle proves that genetic transmission of depigmentation is autosomal dominant.
| Discussion|| |
Gene specific for vitiligo has not been located so far. Appearance of depigmented muzzle among successive generations in the pedigree in [Figure - 2] is due to a gene present in the first generation 1-2. Dog's muzzle is heavily laden with the pigment melanin and the pigment resembles human melanin. It can be an ideal animal model to study genetic inheritance of depigmentation. So a new animal model system was developed using dog's muzzle to demonstrate genetic transmission of depigmentation.
Such study helps in understanding genetic prognosis and genetic counseling when applied to human depigmentation. This study establishes the mode of transmission of the depigmentation through the construction of the pedigree.
In [Figure - 2] the pedigree illustrates the character of depigmented muzzle which is dominant over the pigmented muzzle.
| References|| |
|1.||Nordlund JJ: Vitiligo, Arch Dermatol, 1982; 118: 5-7. |
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]