dog fur

Notes from memory on dog fur color
Lots of papers by Schmutz.

MC1R: melanocortin1 receptor.
 alleles: E. EM (black mask). e. also grizzle/domino allele  in afghans salukis. I forget the symbol and don't understand the phenotype - something about the face? light over eyes?
MC1R is a G-protein-coupled receptor with  7 transmembrane domains; it  activates cAMP.
There are  five melanocortin receptors (e.g. MC1R - MC5R). For MC1R, an agonist is alpha Melanocyte-Stimulating Hormone proopiomelanocortin. Other agonists for melanocortin receptors include ACTH, opioids, satiety.

Tyrosinase: enzyme that coverts  tyrosine to DOPA and DOPA to dopaquinone; both done by tyrosinase. then to either eumelanin or pheomelanin with cysteine
Note: conversion of tyrosine to l-DOPA can also be done by tyrosine hydroxyase, e.g. in Substantia Nigra dopamine cells in the brain.

ASIP or ASP:  agouti signaling protein. (or is it peptide?)
ASIP is an antagonist of alpha MSH, blocks the receptor. This makes production of pheomelanin instead of eumelanin.
Alleles: A^y, a^t, a, a^w
A^y is fawn, yellow to red shades, pheomelanin. A^y is dominant? If e/e, and A^y, no black hairs?
    (Fawn or red-yellow dogs can have black or brown nose, eye rims, pads, because agouti only affects      fur color not skin color.)
a^w is wolf or wild type? wolves have this. agouti or banded hairs on top, light below. keeshonds are an example. (Another gene causes the fawn to be washed out to a cream/white in Keeshonds etc.)  Banded hairs: individual hairs have a tip band of black, then a band of pheomelanin/tan, then another band of black. The ventral side of dog is pale.

a^t is black and tan like a doberman, rottweiler, etc: mostly black (or brown in dogs with bb genotype) but with pheomelanin/tan points - spots over eyes, tips of paws etc.
a is recessive black. some herding breeds, German Shepherd Dog, Belgian sheepdog (Groenendael)

Beta defensin gene makes black by making beta defensin 306? molecule which blocks the ASIP molecule from turning off MC1R. Called K (from 'blacK') in older genetics lit. K is dominant to A.
I think this is limited to dogs and a few other animals - some kind of cattle? Not the typical causeof black animals? There are some other alleles. kb is brindle? k is recessive, no beta defensin made?
K>kb>k? maybe others?

What is the saddle tan mutation - there is paper on this.

Brown color is a result of an allele of tyrosinase-related protein one: tyrp1.
 ? 3 different mutations in gene have been separately linked to brown.   then tyosinase like protein 2 is dopachome tautomerase?
B=dominant = black? b= brown? e.g. chocolate lab? nose, eye rims, pads will also be brown. Euchromatin that makes a brown color instead of black. I don't know why this is, why it looks brown.

Mutation in melanophilin is cause of 'dilute': Weimaraner color, 'blue' Dobermans, Isabella Dobermans. Melanophilin links the melanosome to the actin filament for transport of the melanosome to the keratinocyte. Other proteins arealso involved including a myosin - mysosinVa? Mutation leads to macromelanosomes that do not transport well...?

 SILV has another name with mel in it? CMEL? Is this merle?
double merle: lethal?/ deafness/blindness?

white spotting. Irish. in other animals, often caused by an allele of Kit. In dogs usually it is not caused  by a mutation of Kit. But one line of GSDs had a Kit mutation. Is this MITF?
White spotting is complicated. From small amount on feet, tail tip, muzzle, then chest, neck, around neck, blaze over face, to almost all white except for ears.  Seems like the areas remaining colored are not the same as the tan areas in black and tan dogs. White areas have no melanocytes? This would be a result from the spread of melanoblasts during embryonic development?
And/or melanocytes not making pigments?
See piebald.
See doggenetics.uk site for some details and graphic.

 . . . . . . . . . . . . .
In fish and other  non-mammals, the cells are called melanophores, not melanocytes. The color stays in the cell. In melanocytes, melanin granules are transferred to keratincytes from dendritic parts of melanocytes. In fish, melanin granules transported throughout cell to make dark color or condensed in center to make light color. (or is it the other way?
this is also true in lizards like chameleons.

. . . . . . . . . . . .
Melanoblasts are cells from/in the  neural crest. Melanin granules are related to lysosomes; they are called melanosomes. Melanin is synthesized in the melanosomes by enzymes inside.