INBRED STRAINS
C57BL/6J
JU/Ct/Lm
DBA/2J-Ay/a [dilute (Myo5ad), brown (Tyrp1b),
nonagouti (a)]
YS
All alleles are available congenic with, coisogenic with or
in late stages of backcrossing onto C57BL/6J. The use of inbred congenic stocks,
wherever possible, is highly recommended because this serves as a control
that makes your work directly comparable with the work of others in the field.
(reference my paper and the Ito paper here)
EUMELANIN/PHEOMELANIN
Loci that determine whether the hair follicle pigment cells (melanocytes) produce yellow pheomelanin pigment or nonyellow eumelanin pigment.
Extension (Mc1r) Locus
The Mc1r locus encodes a receptor on the surface of the pigment cell (melanocortin 1 receptor). The receptor can bind MSH (melanocyte stimulating hormone, melanocortin) that is produced outside of the pigment cell. The receptor also can bind the protein encoded at the agouti locus that may be produced in adjacent cells. If MSH is bound to the melanocortin 1 receptor, then the melanogenic genes in the pigment cell are upregulated and eumelanin is produced within the melanocytes. When the agouti protein is bound to the Mc1r receptor, then MSH is unable to bind and the melanogenic genes in the pigment cell are down-regulated and pheomelanin pigment is produced within the pigment cell.
All C57BL/6J and JU/Ct/Lm mice are Mc1rE/Mc1rE unless otherwise stated.
C57BL/6J-Mc1rE-so/Mc1rE-so (sombre)
C57BL/6J-Mc1re/Mc1re (recessive yellow)
C57BL/6J-Mc1re/Mc1re, Tyrc-ch/Tyrc-ch (recessive yellow, chinchilla)
Agouti (A) Locus
The agouti locus encodes a protein that prevents binding of MSH (melanocyte stimulating hormone) to the melanocortin 1 receptor on the surface of the pigment cell. The agouti locus determines when and whether this agouti protein is produced, thus regulating the eumelanin/pheomelanin alternative as described above.
All C57BL/6J and JU/Ct/Lm mice are nonagouti (a/a) unless otherwise stated
DBA/2J-Ay/a
[dilute (Myo5ad), brown (Tyrp1b), nonagouti (a)]
with Ay segregating.
C57/BL/6J-A/A (agouti)
JU/Ct/Lm-Ay/a yellow - This mouse turns dark umbrous at
first molt.
C57BL/6J-Ay/a yellow – Pheomelanic throughout life
C57BL/6J-As/Aw
(agouti suppressor, white-bellied agouti)
C57BL/6J-ae/ae, (extreme non-agouti)
C57BL/6J-au/au (non-agouti umbrous)
C57BL/6J-am/am (mottled agouti) - phenotype ranges
between black, mottled and agouti
C57BL/6J-Ay/a Atrnmg/Atrnmg -Yellow, mahogany
(dark umbrous phenotype)
JU/Ct/Lm-am/am (mottled agouti) - all appear
agouti in phenotype. Also available from cryopreserved stocks at MMRRC,
accession #155
George Wolff’s
classic strain YS, which is viable yellow, piebald (Avy/a, Ednrbs/Ednrbs).
Mahogany (Atrn, attractin) Locus
Mahogany, and several other loci, cause pheomelanin production to be
reduced in mice that are mutant at the agouti locus.
All C57BL/6J and JU/Ct/Lm mice are wild type at the mahogany locus unless
otherwise stated.
C57BL/6J-Ay/a
Atrnmg/Atrnmg – Yellow, mahogany
C57BL/6J-a/a Atrnmg/Atrnmg - Black, mahogany
MELANOGENIC PATHWAY/ALBINISM
The Melanogenic Genes encode enzymes that function in the melanogenic pathway.
Albino
(Tyr) Locus (OCA1)
The albino locus encodes tyrosinase, the enzyme that is necessary for melanin pigment to be produced and therefore is the rate-limiting enzyme in melanogenesis. Tyrosinase production is reduced in pheomelanic melanocytes.
Slaty (Tyrp2) Locus
The slaty locus encodes dopachrome tautomerase (tyrosinase-related protein 2) which is an enzyme of the melanogenic pathway. TRP2 protein is not produced in pheomelanic melanocytes.
C57BL/6J and JU/Ct/Lm mice are not mutant at the slaty locus unless otherwise stated
Black/brown (Tyrp1) Locus (OCA3)
The black/brown locus encodes TRP1 protein (tyrosinase-related protein 1) which is an enzyme of the melanogenic pathway that determines whether eumelanin (if produced) will be black or brown. TRP1 protein is not produced in pheomelanic melanocytes.
All C57BL/6J and JU/Ct/Lm mice are black (Tyrp1B/Tyrp1B) (black) unless otherwise stated.
WHITE SPOTTING (Congenital Absence of Melanocytes)
These loci influence normal migration, replication, differentiation, apoptosis, of pigment cells from the neural crest during embryogenesis. Spotting phenotype and pleiotropic effects differ on the different inbred backgrounds.
Splotch (Pax3) Locus
Homozygous lethal.
Steel (Kitl) Locus
Encodes the kit ligand. May be homozygous lethal. Anemia, white spotting and defects of mast cells and reproductive cells in the heterozygote. The kit protein, carried on the cell surface of affected cell types, must bind the kit ligand protein on adjacent cells for normal development
White (Kit) Locus
May be homozygous lethal. Anemia, white spotting and defects of mast cells and reproductive cells in the heterozygote. The kit protein, carried on the cell surface of affected cell types, must bind the kit ligand protein for normal development.
Rumpwhite (Rw) Locus
Homozygous lethal
Patch (Ph)
Locus
Homozygous lethal.
Microphthalmia
(Mitf) Locus
The Mitf protein is a basic helix-loop-helix transcription factor. Depending
on genotype, birth defects include microphthalmia, retinal degeneration, mast
cell defects, various reproductive defects in male and/or female, osteopetrosis
with absence of teeth, white spotting, progressive pigment loss. peristalsis
abnormality. Other defects have been reported. These stocks are maintained
in several combinations. Most are congenic with C57BL/6J.
Piebald (Ednrb) Locus
For normal development, endothelin receptor B protein, encoded at the piebald locus, must bind endothelin 3, encoded at the lethal-spotting locus. If this does not occur, the resulting birth defects include megacolon and white spotting.
Lethal Spotting (Edn-3) Locus
For normal development, endothelin receptor B protein, encoded at the piebald locus, must bind endothelin 3, encoded at the lethal-spotting locus. If this does not occur, the resulting birth defects include megacolon and white spotting.
Belted (bt) Locus
Belted mice on the C57BL/6J background have a higher-than-normal incidence of hydrocephaly. Recessive yellow belted mice on the same background have a very high incidence of hydrocephaly (unpublished observation).
VITILIGO/FADING PHENOTYPES (Progressive Loss of Pigmentation)
causes of pigment loss may differ. Causes include apoptosis.
Some homozygous or heterozygous combinations of microphthalmia alleles listed under white spotting above exhibit a strong phenotype of progressive loss of pigmentation.
London Grey (Lgr) Locus
Faded (Fe) Locus
Silver (Si) Locus
Silver protein is not produced in pheomelanic melanocytes. Silver phenotype depends upon the background genome. Silver phenotype is expressed more strongly in mice mutant at the Tyrp1 locus.
