A number of American mink phenotypes display
a range of brownish colours. One of these phenotypes,
namely American Palomino (bPbP) (AP) has been found to
be associated with the tyrosinase-related protein 1
(TYRP1) gene by genotyping microsatellite markers in one
sire family. Trials for amplifying the genomic DNA and
cDNA at the beginning of intron 2 of AP TYRP1 revealed
the presence of a large insertion of approximately eight kb.
The insertion most likely disrupts different elements necessary
for the splicing of intron 2 of the TYRP1 gene. In AP
RNAseq data indicate, however, the presence of the wildtype
(wt) transcript at very low levels and Western blot
reveals three products when using an antibody raised
against middle part of the TYRP1 protein. One individual
from another brown mink phenotype—commercially
named Dawn—was also investigated at the molecular level
by long-range PCR and the same size insertion appears to
be present. By this we suggest that certain modifiers of
TYRP1 would induce different brown colour degradation,
which results in at least two different phases of brown.